Brian J Enquist
- Professor, Ecology and Evolutionary Biology
- Member of the Graduate Faculty
- Ph.D. Biology
- University of New Mexico, Albuquerque, New Mexico, United States
- On the origin and consequences of allometric scaling in biology.
- M.S. Biology
- University of New Mexico, Albuquerque, New Mexico, United States
- B.A. Biology
- The Colorado College, Colorado, United States
- with distinction
- Highly Cited Researcher, Web of Science
- Web of Science, Fall 2020
- Web of Science, Fall 2019
- Elected as an Ecological Society of America Fellow (2018)
- Ecological Society of America, Spring 2018
- Leverhulme Professorship – Oxford University, UK (2017)
- The Leverhulme Trust, Spring 2017
- Martin School Fellow – Oxford University, UK (2017)
- The Oxford Martin School, Spring 2017
- American Association for the Advancement of Science (AAAS) Fellow,
- American Association for the Advancement of Science (AAAS), Spring 2012
- Galileo Circle Fellow
- College of Science Galileo Circle Fellow, University of Arizona, 2011., Spring 2011
- Elected Chair of GRC meeting "Metabolic Basis of Ecology and Evolution"
- Gordon Research Conference, Summer 2010
- CNRS Associate Research Fellow
- Centre National de la Recherche Scientifique, France, Fall 2009
- International Mobility Fellow
- Charles University, Center for Theoretical Study, Prague, Czech Republic, 2009, Spring 2009
- Honorary Doctorate in Science,
- The Colorado College, Spring 2007
- ISI Essential Science Indicators (ESI) – Author with the highest percent increase in total citations in the field of Environment/Ecology (2005)
- ISI Essential Science Indicators (ESI)http://www.in-cites.com, Fall 2005
- Top 10 Brilliant Young Scientists
- Popular Science Magazine, Spring 2004
- CABS Science Fellow (2002-2004).
- Conservation International, Spring 2002
- NSF CAREER ‘Young Investigators’ Award (2002-2007)
- National Science Foundation, Spring 2002
- George C. Mercer Award
- Ecological Society of America, Summer 2001
No activities entered.
Directed ResearchBIOC 392 (Fall 2023)
DissertationECOL 920 (Fall 2023)
Evol Of Plan Form+FunctECOL 340 (Fall 2023)
Honors Independent StudyMCB 299H (Fall 2023)
Rsrch Ecology+EvolutionECOL 610A (Fall 2023)
Senior CapstoneBIOC 498 (Fall 2023)
Senior CapstoneBIOC 498 (Summer I 2023)
Directed ResearchBIOC 392 (Spring 2023)
Directed ResearchBIOC 492 (Spring 2023)
Directed RsrchMCB 392 (Spring 2023)
DissertationECOL 920 (Spring 2023)
Independent StudyECOL 599 (Spring 2023)
ResearchECOL 900 (Spring 2023)
Senior CapstoneBIOC 498 (Spring 2023)
DissertationECOL 920 (Fall 2022)
Evol Of Plan Form+FunctECOL 340 (Fall 2022)
Independent StudyECOL 399 (Fall 2022)
ResearchECOL 900 (Fall 2022)
DissertationECOL 920 (Spring 2022)
Honors ThesisMCB 498H (Spring 2022)
ResearchECOL 900 (Spring 2022)
Senior CapstoneBIOC 498 (Spring 2022)
Directed ResearchCHEM 492 (Fall 2021)
DissertationECOL 920 (Fall 2021)
Evol Of Plan Form+FunctECOL 340 (Fall 2021)
Honors ThesisBIOC 498H (Fall 2021)
Honors ThesisMCB 498H (Fall 2021)
ResearchECOL 900 (Fall 2021)
ThesisECOL 910 (Fall 2021)
Independent StudyECOL 499 (Summer I 2021)
Biological ScalingECOL 586 (Spring 2021)
DissertationECOL 920 (Spring 2021)
ResearchECOL 900 (Spring 2021)
DissertationECOL 920 (Fall 2020)
Evol Of Plan Form+FunctECOL 340 (Fall 2020)
ResearchECOL 900 (Fall 2020)
Rsrch Ecology+EvolutionECOL 610A (Fall 2020)
ThesisECOL 910 (Fall 2020)
DissertationECOL 920 (Spring 2020)
Honors Independent StudyMCB 399H (Spring 2020)
Honors ThesisBIOC 498H (Spring 2020)
Independent StudyECOL 299 (Spring 2020)
ResearchECOL 900 (Spring 2020)
Senior CapstoneBIOC 498 (Spring 2020)
Spc Tps Ecol+Evol AECOL 596W (Spring 2020)
Directed ResearchBIOC 392 (Fall 2019)
Directed ResearchBIOC 492 (Fall 2019)
DissertationECOL 920 (Fall 2019)
Evol Of Plan Form+FunctECOL 340 (Fall 2019)
Honors Independent StudyMCB 299H (Fall 2019)
Honors ThesisBIOC 498H (Fall 2019)
Independent StudyECOL 299 (Fall 2019)
ResearchECOL 900 (Fall 2019)
Biological ScalingECOL 586 (Spring 2019)
Directed ResearchBIOC 492 (Spring 2019)
Directed ResearchCHEM 492 (Spring 2019)
Directed ResearchECOL 392 (Spring 2019)
Independent StudyECOL 299 (Spring 2019)
Independent StudyECOL 399 (Spring 2019)
Population BiologyECOL 596B (Spring 2019)
ResearchECOL 900 (Spring 2019)
Senior CapstoneBIOC 498 (Spring 2019)
Directed ResearchBIOC 392 (Fall 2018)
Directed ResearchCHEM 392 (Fall 2018)
Evol Of Plan Form+FunctECOL 340 (Fall 2018)
Independent StudyECOL 199 (Fall 2018)
Independent StudyECOL 399 (Fall 2018)
Independent StudyECOL 499 (Fall 2018)
ResearchECOL 900 (Fall 2018)
Senior CapstoneBIOC 498 (Fall 2018)
Biological ScalingECOL 586 (Spring 2018)
Independent StudyECOL 299 (Spring 2018)
Independent StudyECOL 399 (Spring 2018)
Independent StudyECOL 499 (Spring 2018)
Independent StudyMIC 399 (Spring 2018)
ResearchECOL 900 (Spring 2018)
Directed ResearchCHEM 392 (Fall 2017)
Evol Of Plan Form+FunctECOL 340 (Fall 2017)
Honors ThesisECOL 498H (Fall 2017)
Independent StudyECOL 299 (Fall 2017)
Independent StudyECOL 599 (Fall 2017)
ResearchECOL 900 (Fall 2017)
Rsrch Ecology+EvolutionECOL 610A (Fall 2017)
Spc Tps Ecol+Evol BECOL 596X (Fall 2017)
Directed ResearchECOL 392 (Spring 2017)
DissertationECOL 920 (Spring 2017)
DissertationPHYS 920 (Spring 2017)
Honors Independent StudyECOL 499H (Spring 2017)
Honors ThesisECOL 498H (Spring 2017)
Independent StudyECOL 399 (Spring 2017)
Independent StudyECOL 499 (Spring 2017)
ResearchECOL 900 (Spring 2017)
Rsrch Ecology+EvolutionECOL 610A (Spring 2017)
Senior CapstoneBIOC 498 (Spring 2017)
Directed ResearchBIOC 392 (Fall 2016)
DissertationECOL 920 (Fall 2016)
DissertationPHYS 920 (Fall 2016)
Honors Independent StudyECOL 399H (Fall 2016)
Honors Independent StudyECOL 499H (Fall 2016)
ResearchECOL 900 (Fall 2016)
Rsrch Ecology+EvolutionECOL 610A (Fall 2016)
Senior CapstoneBIOC 498 (Fall 2016)
Spc Tps Ecol+Evol BECOL 596X (Fall 2016)
ThesisECOL 910 (Fall 2016)
DissertationECOL 920 (Spring 2016)
DissertationPHYS 920 (Spring 2016)
Honors Independent StudyECOL 299H (Spring 2016)
Honors Independent StudyECOL 499H (Spring 2016)
Independent StudyECOL 199 (Spring 2016)
Independent StudyECOL 299 (Spring 2016)
Independent StudyECOL 399 (Spring 2016)
Independent StudyECOL 499 (Spring 2016)
ResearchECOL 900 (Spring 2016)
ThesisECOL 910 (Spring 2016)
- Burger, J. R., Okie, J. G., Hatton, I., Weinberger, V. P., Shrestha, M., Liedtke, K. J., Be, T., Cruz, A. R., Feng, X., Hinojo-Hinojo, C., Kibria, A. S., Ernst, K. C., & Enquist, B. J. (2023). Global city densities: re-examining urban scaling theory.More infoUnderstanding scaling relations of social and environmental attributes ofurban systems is necessary for effectively managing cities. Urban scalingtheory (UST) has assumed that population density scales positively with citysize. We present a new global analysis using a publicly available database of933 cities from 38 countries. Our results showed that (18/38) 47% of countriesanalyzed supported increasing density scaling (pop ~ area) with exponents ~5/6as UST predicts. In contrast, 17 of 38 countries (~45%) exhibited densityscalings statistically indistinguishable from constant population densitiesacross cities of varying sizes. These results were generally consistent inyears spanning four decades from 1975 to 2015. Importantly, density varies byan order of magnitude between regions and countries and decreases in moredeveloped economies. Our results (i) point to how economic and regionaldifferences may affect the scaling of density with city size and (ii) show howunderstanding country- and region-specific strategies could inform effectivemanagement of urban systems for biodiversity, public health, conservation andresiliency from local to global scales.[Journal_ref: ]
- Chacón-Labella, J., Hinojo-Hinojo, C., Bohner, T., Castorena, M., Violle, C., Vandvik, V., & Enquist, B. J. (2023). How to improve scaling from traits to ecosystem processes. Trends in ecology & evolution, 38(3), 228-237.More infoScaling approaches in ecology assume that traits are the main attributes by which organisms influence ecosystem functioning. However, several recent empirical papers have found only weak links between traits and ecosystem functioning, questioning the usefulness of trait-based ecology (TBE). We argue that these studies often suffer from one or more widespread misconceptions. Specifically, these studies often (i) conflict with the conceptual foundations of TBE, (ii) lack theory- or hypothesis-driven selection and use of traits, (iii) tend to ignore intraspecific variation, and (iv) use experimental or study designs that are not well suited to make strong tests of TBE assumptions. Addressing these aspects could significantly improve our ability to scale from traits to ecosystem functioning.
- Merow, C., Boyle, B., Enquist, B. J., Feng, X., Kass, J. M., Maitner, B. S., McGill, B., Owens, H., Park, D. S., Paz, A., Pinilla-Buitrago, G. E., Urban, M. C., Varela, S., & Wilson, A. M. (2023). Better incentives are needed to reward academic software development. Nature ecology & evolution.
- Xu, W. B., Guo, W. Y., Serra-Diaz, J. M., Schrodt, F., Eiserhardt, W. L., Enquist, B. J., Maitner, B. S., Merow, C., Violle, C., Anand, M., Belluau, M., Bruun, H. H., Byun, C., Catford, J. A., Cerabolini, B. E., Chacón-Madrigal, E., Ciccarelli, D., Cornelissen, J. H., Dang-Le, A. T., , de Frutos, A., et al. (2023). Global beta-diversity of angiosperm trees is shaped by Quaternary climate change. Science advances, 9(14), eadd8553.More infoAs Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleoclimate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (richness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta-diversity in regions that experienced large temperature change, reflecting phylogenetically and functionally selective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide.
- , A. B., , P. L., , J. S., , E. T., , L. P., , V. B., , A. G., , I. O., , B. J., & , V. M. (2022). Branching principles of animal and plant networks identified by combining extensive data, machine learning, and modeling.More infoBranching in vascular networks and in overall organismic form is one of themost common and ancient features of multicellular plants, fungi, and animals.By combining machine-learning techniques with new theory that relates vascularform to metabolic function, we enable novel classification of diverse branchingnetworks--mouse lung, human head and torso, angiosperm and gymnosperm plants.We find that ratios of limb radii--which dictate essential biologic functionsrelated to resource transport and supply--are best at distinguishing branchingnetworks. We also show how variation in vascular and branching geometrypersists despite observing a convergent relationship across organisms for howmetabolic rate depends on body mass.[Journal_ref: ]
- , G. B., , V. M., , J. G., , B. J., , W. H., & , J. H. (2022). Red herrings and rotten fish.More infoA longstanding problem in biology has been the origin of pervasivequarter-power allometric scaling laws that relate many characteristics oforganisms to body mass (M) across the entire spectrum of life from moleculesand microbes to ecosystems and mammals. In particular, whole-organism metabolicrate, B=aM^b, where a is a taxon-dependent normalisation constant and b isapproximately equal to 3/4 for both animals and plants. Recently Darveau et al.(hereafter referred to as DSAH) proposed a "multiple-causes model" for B as"the sum of multiple contributors to metabolism", B_i, which were assumed toscale as M^(b_i). They obtained for average values of b: 0.78 for the basalrate and 0.86 for the maximally active rate. In this note we show that DSAHcontains serious technical, theoretical and conceptual errors, includingmisrepresentations of published data and of our previous work. We also showthat, within experimental error, there is no empirical evidence for an increasein b during aerobic activity as suggested by DSAH. Moreover, since DSAHconsider only metabolic rates of mammals and make no attempt to explain whymetabolic rates for other taxa and many other attributes in diverse organismsalso scale with quarter-powers (including most of their input data), theirformulation is hardly the "unifying principle" they claim. These problems werenot addressed in commentaries by Weibel and Burness.[Journal_ref: ]
- Aguirre-Gutiérrez, J., Berenguer, E., Oliveras Menor, I., Bauman, D., Corral-Rivas, J. J., Nava-Miranda, M. G., Both, S., Ndong, J. E., Ondo, F. E., Bengone, N. N., Mihinhou, V., Dalling, J. W., Heineman, K., Figueiredo, A., González-M, R., Norden, N., Hurtado-M, A. B., González, D., Salgado-Negret, B., , Reis, S. M., et al. (2022). Functional susceptibility of tropical forests to climate change. Nature ecology & evolution, 6(7), 878-889.More infoTropical forests are some of the most biodiverse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forests' functional diversity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional diversity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits sampled from 2,461 individual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional diversity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally diverse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional diversity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional diversity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.
- Boyle, B. L., Maitner, B. S., Barbosa, G. G., Sajja, R. K., Feng, X., Merow, C., Newman, E. A., Park, D. S., Roehrdanz, P. R., & Enquist, B. J. (2022). Geographic name resolution service: A tool for the standardization and indexing of world political division names, with applications to species distribution modeling. PloS one, 17(11), e0268162.More infoMassive biological databases of species occurrences, or georeferenced locations where a species has been observed, are essential inputs for modeling present and future species distributions. Location accuracy is often assessed by determining whether the observation geocoordinates fall within the boundaries of the declared political divisions. This otherwise simple validation is complicated by the difficulty of matching political division names to the correct geospatial object. Spelling errors, abbreviations, alternative codes, and synonyms in multiple languages present daunting name disambiguation challenges. The inability to resolve political division names reduces usable data, and analysis of erroneous observations can lead to flawed results. Here, we present the Geographic Name Resolution Service (GNRS), an application for correcting, standardizing, and indexing world political division names. The GNRS resolves political division names against a reference database that combines names and codes from GeoNames with geospatial object identifiers from the Global Administrative Areas Database (GADM). In a trial resolution of political division names extracted from >270 million species occurrences, only 1.9%, representing just 6% of occurrences, matched exactly to GADM political divisions in their original form. The GNRS was able to resolve, completely or in part, 92% of the remaining 378,568 political division names, or 86% of the full biodiversity occurrence dataset. In assessing geocoordinate accuracy for >239 million species occurrences, resolution of political divisions by the GNRS enabled the detection of an order of magnitude more errors and an order of magnitude more error-free occurrences. By providing a novel solution to a significant data quality impediment, the GNRS liberates a tremendous amount of biodiversity data for quantitative biodiversity research. The GNRS runs as a web service and is accessible via an API, an R package, and a web-based graphical user interface. Its modular architecture is easily integrated into existing data validation workflows.
- Brun, P., Violle, C., Mouillot, D., Mouquet, N., Enquist, B. J., Munoz, F., Münkemüller, T., Ostling, A., Zimmermann, N. E., & Thuiller, W. (2022). Plant community impact on productivity: Trait diversity or key(stone) species effects?. Ecology letters, 25(4), 913-925.More infoOutside controlled experimental plots, the impact of community attributes on primary productivity has rarely been compared to that of individual species. Here, we identified plant species of high importance for productivity (key species) in >29,000 diverse grassland communities in the European Alps, and compared their effects with those of community-level measures of functional composition (weighted means, variances, skewness and kurtosis). After accounting for the environment, the five most important key species jointly explained more deviance of productivity than any measure of functional composition alone. Key species were generally tall with high specific leaf areas. By dividing the observations according to distinct habitats, the explanatory power of key species and functional composition increased and key-species plant types and functional composition-productivity relationships varied systematically, presumably because of changing interactions and trade-offs between traits. Our results advocate for a careful consideration of species' individual effects on ecosystem functioning in complement to community-level measures.
- Castorena, M., Olson, M. E., Enquist, B. J., & Fajardo, A. (2022). Toward a general theory of plant carbon economics. Trends in ecology & evolution, 37(10), 829-837.More infoPlant life-history variation reflects different outcomes of natural selection given the strictures of resource allocation trade-offs. However, there is limited theory of selection predicting how leaves, stems, roots, and reproductive organs should evolve in concert across environments. Here, we synthesize two optimality theories to offer a general theory of plant carbon economics, named as Gmax theory, that shows how life-history variation is limited to phenotypes that have an approximately similar lifetime net carbon gain per body mass. In consequence, fast-slow economics spectra are the result of trait combinations obtaining similar lifetime net carbon gains from leaves and similar net carbon investment costs in stems, roots, and reproductive organs. Gmax theory also helps explain ecosystem and crop productivity and even helps guide carbon conservation strategies.
- Cazzolla Gatti, R., Reich, P. B., Gamarra, J. G., Crowther, T., Hui, C., Morera, A., Bastin, J. F., de-Miguel, S., Nabuurs, G. J., Svenning, J. C., Serra-Diaz, J. M., Merow, C., Enquist, B., Kamenetsky, M., Lee, J., Zhu, J., Fang, J., Jacobs, D. F., Pijanowski, B., , Banerjee, A., et al. (2022). The number of tree species on Earth. Proceedings of the National Academy of Sciences of the United States of America, 119(6).More infoOne of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.
- Chaplin-Kramer, R., Brauman, K. A., Cavender-Bares, J., Díaz, S., Duarte, G. T., Enquist, B. J., Garibaldi, L. A., Geldmann, J., Halpern, B. S., Hertel, T. W., Khoury, C. K., Krieger, J. M., Lavorel, S., Mueller, T., Neugarten, R. A., Pinto-Ledezma, J., Polasky, S., Purvis, A., Reyes-García, V., , Roehrdanz, P. R., et al. (2022). Conservation needs to integrate knowledge across scales. Nature ecology & evolution, 6(2), 118-119.
- Díaz, S., Kattge, J., Cornelissen, J. H., Wright, I. J., Lavorel, S., Dray, S., Reu, B., Kleyer, M., Wirth, C., Prentice, I. C., Garnier, E., Bönisch, G., Westoby, M., Poorter, H., Reich, P. B., Moles, A. T., Dickie, J., Zanne, A. E., Chave, J., , Wright, S. J., et al. (2022). The global spectrum of plant form and function: enhanced species-level trait dataset. Scientific data, 9(1), 755.More infoHere we provide the 'Global Spectrum of Plant Form and Function Dataset', containing species mean values for six vascular plant traits. Together, these traits -plant height, stem specific density, leaf area, leaf mass per area, leaf nitrogen content per dry mass, and diaspore (seed or spore) mass - define the primary axes of variation in plant form and function. The dataset is based on ca. 1 million trait records received via the TRY database (representing ca. 2,500 original publications) and additional unpublished data. It provides 92,159 species mean values for the six traits, covering 46,047 species. The data are complemented by higher-level taxonomic classification and six categorical traits (woodiness, growth form, succulence, adaptation to terrestrial or aquatic habitats, nutrition type and leaf type). Data quality management is based on a probabilistic approach combined with comprehensive validation against expert knowledge and external information. Intense data acquisition and thorough quality control produced the largest and, to our knowledge, most accurate compilation of empirically observed vascular plant species mean traits to date.
- Guo, W. Y., Serra-Diaz, J. M., Schrodt, F., Eiserhardt, W. L., Maitner, B. S., Merow, C., Violle, C., Anand, M., Belluau, M., Bruun, H. H., Byun, C., Catford, J. A., Cerabolini, B. E., Chacón-Madrigal, E., Ciccarelli, D., Cornelissen, J. H., Dang-Le, A. T., de Frutos, A., Dias, A. S., , Giroldo, A. B., et al. (2022). High exposure of global tree diversity to human pressure. Proceedings of the National Academy of Sciences of the United States of America, 119(25), e2026733119.More infoSafeguarding Earth's tree diversity is a conservation priority due to the importance of trees for biodiversity and ecosystem functions and services such as carbon sequestration. Here, we improve the foundation for effective conservation of global tree diversity by analyzing a recently developed database of tree species covering 46,752 species. We quantify range protection and anthropogenic pressures for each species and develop conservation priorities across taxonomic, phylogenetic, and functional diversity dimensions. We also assess the effectiveness of several influential proposed conservation prioritization frameworks to protect the top 17% and top 50% of tree priority areas. We find that an average of 50.2% of a tree species' range occurs in 110-km grid cells without any protected areas (PAs), with 6,377 small-range tree species fully unprotected, and that 83% of tree species experience nonnegligible human pressure across their range on average. Protecting high-priority areas for the top 17% and 50% priority thresholds would increase the average protected proportion of each tree species' range to 65.5% and 82.6%, respectively, leaving many fewer species (2,151 and 2,010) completely unprotected. The priority areas identified for trees match well to the Global 200 Ecoregions framework, revealing that priority areas for trees would in large part also optimize protection for terrestrial biodiversity overall. Based on range estimates for >46,000 tree species, our findings show that a large proportion of tree species receive limited protection by current PAs and are under substantial human pressure. Improved protection of biodiversity overall would also strongly benefit global tree diversity.
- Lourenço, J., Enquist, B. J., von Arx, G., Sonsin-Oliveira, J., Morino, K., Thomaz, L. D., & Milanez, C. R. (2022). Hydraulic tradeoffs underlie local variation in tropical forest functional diversity and sensitivity to drought. The New phytologist, 234(1), 50-63.More infoTropical forests are important to the regulation of climate and the maintenance of biodiversity on Earth. However, these ecosystems are threatened by climate change, as temperatures rise and droughts' frequency and duration increase. Xylem anatomical traits are an essential component in understanding and predicting forest responses to changes in water availability. We calculated the community-weighted means and variances of xylem anatomical traits of hydraulic and structural importance (plot-level trait values weighted by species abundance) to assess their linkages to local adaptation and community assembly in response to varying soil water conditions in an environmentally diverse Brazilian Atlantic Forest habitat. Scaling approaches revealed community-level tradeoffs in xylem traits not observed at the species level. Towards drier sites, xylem structural reinforcement and integration balanced against hydraulic efficiency and capacitance xylem traits, leading to changes in plant community diversity. We show how general community assembly rules are reflected in persistent fiber-parenchyma and xylem hydraulic tradeoffs. Trait variation across a moisture gradient is larger between species than within species and is realized mainly through changes in species composition and abundance, suggesting habitat specialization. Modeling efforts to predict tropical forest diversity and drought sensitivity may benefit from adding hydraulic architecture traits into the analysis.
- Pillet, M., Goettsch, B., Merow, C., Maitner, B., Feng, X., Roehrdanz, P. R., & Enquist, B. J. (2022). Elevated extinction risk of cacti under climate change. Nature plants, 8(4), 366-372.More infoCactaceae (cacti), a New World plant family, is one of the most endangered groups of organisms on the planet. Conservation planning is uncertain as it is unclear whether climate and land-use change will positively or negatively impact global cactus diversity. On the one hand, a common perception is that future climates will be favourable to cacti as they have multiple adaptations and specialized physiologies and morphologies for increased heat and drought. On the other hand, the wide diversity of the more than 1,500 cactus species, many of which occur in more mesic and cooler ecosystems, questions the view that most cacti can tolerate warmer and drought conditions. Here we assess the hypothesis that cacti will benefit and expand in potential distribution in a warmer and more drought-prone world. We quantified exposure to climate change through range forecasts and associated diversity maps for 408 cactus species under three Representative Concentration Pathways (2.6, 4.5 and 8.5) for 2050 and 2070. Our analyses show that 60% of species will experience a reduction in favourable climate, with about a quarter of species exposed to environmental conditions outside of the current realized niche in over 25% of their current distribution. These results show low sensitivity to many uncertainties in forecasting, mostly deriving from dispersal ability and model complexity rather than climate scenarios. While current range size and the International Union for Conservation of Nature's Red List category were not statistically significant predictors of predicted future changes in suitable climate area, epiphytes had the greatest exposure to novel climates. Overall, the number of cactus species at risk is projected to increase sharply in the future, especially in current richness hotspots. Land-use change has previously been identified as the second-most-common driver of threat among cacti, affecting many of the ~31% of cacti that are currently threatened. Our results suggest that climate change will become a primary driver of cactus extinction risk with 60-90% of species assessed negatively impacted by climate change and/or other anthropogenic processes, depending on how these threat processes are distributed across cactus species.
- Brummer, A. B., Lymperopoulos, P., Shen, J., Tekin, E., Bentley, L. P., Buzzard, V., Gray, A., Oliveras, I., Enquist, B. J., & Savage, V. M. (2021). Branching principles of animal and plant networks identified by combining extensive data, machine learning and modelling. Journal of the Royal Society, Interface, 18(174), 20200624.More infoBranching in vascular networks and in overall organismic form is one of the most common and ancient features of multicellular plants, fungi and animals. By combining machine-learning techniques with new theory that relates vascular form to metabolic function, we enable novel classification of diverse branching networks-mouse lung, human head and torso, angiosperm and gymnosperm plants. We find that ratios of limb radii-which dictate essential biologic functions related to resource transport and supply-are best at distinguishing branching networks. We also show how variation in vascular and branching geometry persists despite observing a convergent relationship across organisms for how metabolic rate depends on body mass.
- Chacón-Labella, J., Boakye, M., Enquist, B. J., Farfan-Rios, W., Gya, R., Halbritter, A. H., Middleton, S. L., von Oppen, J., Pastor-Ploskonka, S., Strydom, T., Vandvik, V., & Geange, S. R. (2021). From a crisis to an opportunity: Eight insights for doing science in the COVID-19 era and beyond. Ecology and evolution, 11(8), 3588-3596.More infoThe COVID-19 crisis has forced researchers in Ecology to change the way we work almost overnight. Nonetheless, the pandemic has provided us with several novel components for a new way of conducting science. In this perspective piece, we summarize eight central insights that are helping us, as early career researchers, navigate the uncertainties, fears, and challenges of advancing science during the COVID-19 pandemic. We highlight how innovative, collaborative, and often Open Science-driven developments that have arisen from this crisis can form a blueprint for a community reinvention in academia. Our insights include personal approaches to managing our new reality, maintaining capacity to focus and resilience in our projects, and a variety of tools that facilitate remote collaboration. We also highlight how, at a community level, we can take advantage of online communication platforms for gaining accessibility to conferences and meetings, and for maintaining research networks and community engagement while promoting a more diverse and inclusive community. Overall, we are confident that these practices can support a more inclusive and kinder scientific culture for the longer term.
- Feng, X., Merow, C., Liu, Z., Park, D. S., Roehrdanz, P. R., Maitner, B., Newman, E. A., Boyle, B. L., Lien, A., Burger, J. R., Pires, M. M., Brando, P. M., Bush, M. B., McMichael, C. N., Neves, D. M., Nikolopoulos, E. I., Saleska, S. R., Hannah, L., Breshears, D. D., , Evans, T. P., et al. (2021). How deregulation, drought and increasing fire impact Amazonian biodiversity. Nature, 597(7877), 516-521.More infoBiodiversity contributes to the ecological and climatic stability of the Amazon Basin, but is increasingly threatened by deforestation and fire. Here we quantify these impacts over the past two decades using remote-sensing estimates of fire and deforestation and comprehensive range estimates of 11,514 plant species and 3,079 vertebrate species in the Amazon. Deforestation has led to large amounts of habitat loss, and fires further exacerbate this already substantial impact on Amazonian biodiversity. Since 2001, 103,079-189,755 km of Amazon rainforest has been impacted by fires, potentially impacting the ranges of 77.3-85.2% of species that are listed as threatened in this region. The impacts of fire on the ranges of species in Amazonia could be as high as 64%, and greater impacts are typically associated with species that have restricted ranges. We find close associations between forest policy, fire-impacted forest area and their potential impacts on biodiversity. In Brazil, forest policies that were initiated in the mid-2000s corresponded to reduced rates of burning. However, relaxed enforcement of these policies in 2019 has seemingly begun to reverse this trend: approximately 4,253-10,343 km of forest has been impacted by fire, leading to some of the most severe potential impacts on biodiversity since 2009. These results highlight the critical role of policy enforcement in the preservation of biodiversity in the Amazon.
- Geange, S. R., von Oppen, J., Strydom, T., Boakye, M., Gauthier, T. J., Gya, R., Halbritter, A. H., Jessup, L. H., Middleton, S. L., Navarro, J., Pierfederici, M. E., Chacón-Labella, J., Cotner, S., Farfan-Rios, W., Maitner, B. S., Michaletz, S. T., Telford, R. J., Enquist, B. J., & Vandvik, V. (2021). Next-generation field courses: Integrating Open Science and online learning. Ecology and evolution, 11(8), 3577-3587.More infoAs Open Science practices become more commonplace, there is a need for the next generation of scientists to be well versed in these aspects of scientific research. Yet, many training opportunities for early career researchers (ECRs) could better emphasize or integrate Open Science elements. Field courses provide opportunities for ECRs to apply theoretical knowledge, practice new methodological approaches, and gain an appreciation for the challenges of real-life research, and could provide an excellent platform for integrating training in Open Science practices. Our recent experience, as primarily ECRs engaged in a field course interrupted by COVID-19, led us to reflect on the potential to enhance learning outcomes in field courses by integrating Open Science practices and online learning components. Specifically, we highlight the opportunity for field courses to align teaching activities with the recent developments and trends in how we conduct research, including training in: publishing registered reports, collecting data using standardized methods, adopting high-quality data documentation, managing data through reproducible workflows, and sharing and publishing data through appropriate channels. We also discuss how field courses can use online tools to optimize time in the field, develop open access resources, and cultivate collaborations. By integrating these elements, we suggest that the next generation of field courses will offer excellent arenas for participants to adopt Open Science practices.
- Jung, M., Arnell, A., de Lamo, X., García-Rangel, S., Lewis, M., Mark, J., Merow, C., Miles, L., Ondo, I., Pironon, S., Ravilious, C., Rivers, M., Schepaschenko, D., Tallowin, O., van Soesbergen, A., Govaerts, R., Boyle, B. L., Enquist, B. J., Feng, X., , Gallagher, R., et al. (2021). Author Correction: Areas of global importance for conserving terrestrial biodiversity, carbon and water. Nature ecology & evolution, 5(11), 1557.
- Jung, M., Jung, M., Jung, M., Arnell, A., Arnell, A., Arnell, A., de Lamo, X., de Lamo, X., de Lamo, X., García-Rangel, S., García-Rangel, S., García-Rangel, S., Lewis, M., Lewis, M., Lewis, M., Mark, J., Mark, J., Mark, J., Merow, C., , Merow, C., et al. (2021). Areas of global importance for conserving terrestrial biodiversity, carbon and water. Nature ecology & evolution, 5(11), 1499-1509.More infoTo meet the ambitious objectives of biodiversity and climate conventions, the international community requires clarity on how these objectives can be operationalized spatially and how multiple targets can be pursued concurrently. To support goal setting and the implementation of international strategies and action plans, spatial guidance is needed to identify which land areas have the potential to generate the greatest synergies between conserving biodiversity and nature's contributions to people. Here we present results from a joint optimization that minimizes the number of threatened species, maximizes carbon retention and water quality regulation, and ranks terrestrial conservation priorities globally. We found that selecting the top-ranked 30% and 50% of terrestrial land area would conserve respectively 60.7% and 85.3% of the estimated total carbon stock and 66% and 89.8% of all clean water, in addition to meeting conservation targets for 57.9% and 79% of all species considered. Our data and prioritization further suggest that adequately conserving all species considered (vertebrates and plants) would require giving conservation attention to ~70% of the terrestrial land surface. If priority was given to biodiversity only, managing 30% of optimally located land area for conservation may be sufficient to meet conservation targets for 81.3% of the terrestrial plant and vertebrate species considered. Our results provide a global assessment of where land could be optimally managed for conservation. We discuss how such a spatial prioritization framework can support the implementation of the biodiversity and climate conventions.
- Kemppinen, J., Kemppinen, J., Niittynen, P., Niittynen, P., le Roux, P. C., le Roux, P. C., Momberg, M., Momberg, M., Happonen, K., Happonen, K., Aalto, J., Aalto, J., Rautakoski, H., Rautakoski, H., Enquist, B. J., Enquist, B. J., Vandvik, V., Vandvik, V., Halbritter, A. H., , Halbritter, A. H., et al. (2021). Consistent trait-environment relationships within and across tundra plant communities. Nature ecology & evolution, 5(4), 458-467.More infoA fundamental assumption in trait-based ecology is that relationships between traits and environmental conditions are globally consistent. We use field-quantified microclimate and soil data to explore if trait-environment relationships are generalizable across plant communities and spatial scales. We collected data from 6,720 plots and 217 species across four distinct tundra regions from both hemispheres. We combined these data with over 76,000 database trait records to relate local plant community trait composition to broad gradients of key environmental drivers: soil moisture, soil temperature, soil pH and potential solar radiation. Results revealed strong, consistent trait-environment relationships across Arctic and Antarctic regions. This indicates that the detected relationships are transferable between tundra plant communities also when fine-scale environmental heterogeneity is accounted for, and that variation in local conditions heavily influences both structural and leaf economic traits. Our results strengthen the biological and mechanistic basis for climate change impact predictions of vulnerable high-latitude ecosystems.
- Neves, D. M., Kerkhoff, A. J., Echeverría-Londoño, S., Merow, C., Morueta-Holme, N., Peet, R. K., Sandel, B., Svenning, J. C., Wiser, S. K., & Enquist, B. J. (2021). The adaptive challenge of extreme conditions shapes evolutionary diversity of plant assemblages at continental scales. Proceedings of the National Academy of Sciences of the United States of America, 118(37).More infoThe tropical conservatism hypothesis (TCH) posits that the latitudinal gradient in biological diversity arises because most extant clades of animals and plants originated when tropical environments were more widespread and because the colonization of colder and more seasonal temperate environments is limited by the phylogenetically conserved environmental tolerances of these tropical clades. Recent studies have claimed support of the TCH, indicating that temperate plant diversity stems from a few more recently derived lineages that are nested within tropical clades, with the colonization of the temperate zone being associated with key adaptations to survive colder temperatures and regular freezing. Drought, however, is an additional physiological stress that could shape diversity gradients. Here, we evaluate patterns of evolutionary diversity in plant assemblages spanning the full extent of climatic gradients in North and South America. We find that in both hemispheres, extratropical dry biomes house the lowest evolutionary diversity, while tropical moist forests and many temperate mixed forests harbor the highest. Together, our results support a more nuanced view of the TCH, with environments that are radically different from the ancestral niche of angiosperms having limited, phylogenetically clustered diversity relative to environments that show lower levels of deviation from this niche. Thus, we argue that ongoing expansion of arid environments is likely to entail higher loss of evolutionary diversity not just in the wet tropics but in many extratropical moist regions as well.
- Enquist, B. J., Abraham, A. J., Harfoot, M. B., Malhi, Y., & Doughty, C. E. (2020). The megabiota are disproportionately important for biosphere functioning. Nature communications, 11(1), 699.More infoA prominent signal of the Anthropocene is the extinction and population reduction of the megabiota-the largest animals and plants on the planet. However, we lack a predictive framework for the sensitivity of megabiota during times of rapid global change and how they impact the functioning of ecosystems and the biosphere. Here, we extend metabolic scaling theory and use global simulation models to demonstrate that (i) megabiota are more prone to extinction due to human land use, hunting, and climate change; (ii) loss of megabiota has a negative impact on ecosystem metabolism and functioning; and (iii) their reduction has and will continue to significantly decrease biosphere functioning. Global simulations show that continued loss of large animals alone could lead to a 44%, 18% and 92% reduction in terrestrial heterotrophic biomass, metabolism, and fertility respectively. Our findings suggest that policies that emphasize the promotion of large trees and animals will have disproportionate impact on biodiversity, ecosystem processes, and climate mitigation.
- Gallagher, R. V., Falster, D. S., Maitner, B. S., Salguero-Gómez, R., Vandvik, V., Pearse, W. D., Schneider, F. D., Kattge, J., Poelen, J. H., Madin, J. S., Ankenbrand, M. J., Penone, C., Feng, X., Adams, V. M., Alroy, J., Andrew, S. C., Balk, M. A., Bland, L. M., Boyle, B. L., , Bravo-Avila, C. H., et al. (2020). Open Science principles for accelerating trait-based science across the Tree of Life. Nature ecology & evolution, 4(3), 294-303.More infoSynthesizing trait observations and knowledge across the Tree of Life remains a grand challenge for biodiversity science. Species traits are widely used in ecological and evolutionary science, and new data and methods have proliferated rapidly. Yet accessing and integrating disparate data sources remains a considerable challenge, slowing progress toward a global synthesis to integrate trait data across organisms. Trait science needs a vision for achieving global integration across all organisms. Here, we outline how the adoption of key Open Science principles-open data, open source and open methods-is transforming trait science, increasing transparency, democratizing access and accelerating global synthesis. To enhance widespread adoption of these principles, we introduce the Open Traits Network (OTN), a global, decentralized community welcoming all researchers and institutions pursuing the collaborative goal of standardizing and integrating trait data across organisms. We demonstrate how adherence to Open Science principles is key to the OTN community and outline five activities that can accelerate the synthesis of trait data across the Tree of Life, thereby facilitating rapid advances to address scientific inquiries and environmental issues. Lessons learned along the path to a global synthesis of trait data will provide a framework for addressing similarly complex data science and informatics challenges.
- Gallagher, R. V., Gallagher, R. V., Falster, D. S., Falster, D. S., Maitner, B. S., Maitner, B. S., Salguero-Gómez, R., Salguero-Gómez, R., Vandvik, V., Vandvik, V., Pearse, W. D., Pearse, W. D., Schneider, F. D., Schneider, F. D., Kattge, J., Kattge, J., Poelen, J. H., Poelen, J. H., Madin, J. S., , Madin, J. S., et al. (2020). Publisher Correction: Open Science principles for accelerating trait-based science across the Tree of Life. Nature ecology & evolution, 4(4), 662.More infoAn amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Li, Y., Reich, P. B., Schmid, B., Shrestha, N., Feng, X., Lyu, T., Maitner, B. S., Xu, X., Li, Y., Zou, D., Tan, Z. H., Su, X., Tang, Z., Guo, Q., Feng, X., Enquist, B. J., & Wang, Z. (2020). Leaf size of woody dicots predicts ecosystem primary productivity. Ecology letters, 23(6), 1003-1013.More infoA key challenge in ecology is to understand the relationships between organismal traits and ecosystem processes. Here, with a novel dataset of leaf length and width for 10 480 woody dicots in China and 2374 in North America, we show that the variation in community mean leaf size is highly correlated with the variation in climate and ecosystem primary productivity, independent of plant life form. These relationships likely reflect how natural selection modifies leaf size across varying climates in conjunction with how climate influences canopy total leaf area. We find that the leaf size-primary productivity functions based on the Chinese dataset can predict productivity in North America and vice-versa. In addition to advancing understanding of the relationship between a climate-driven trait and ecosystem functioning, our findings suggest that leaf size can also be a promising tool in palaeoecology for scaling from fossil leaves to palaeo-primary productivity of woody ecosystems.
- Park, D. S., Feng, X., Maitner, B. S., Ernst, K. C., & Enquist, B. J. (2020). Darwin's naturalization conundrum can be explained by spatial scale. Proceedings of the National Academy of Sciences of the United States of America, 117(20), 10904-10910.More infoDarwin proposed two seemingly contradictory hypotheses regarding factors influencing the outcome of biological invasions. He initially posited that nonnative species closely related to native species would be more likely to successfully establish, because they might share adaptations to the local environment (preadaptation hypothesis). However, based on observations that the majority of naturalized plant species in the United States belonged to nonnative genera, he concluded that the lack of competitive exclusion would facilitate the establishment of alien invaders phylogenetically distinct from the native flora (competition-relatedness hypothesis). To date, no consensus has been reached regarding these opposing hypotheses. Here, following Darwin, we use the flora of the United States to examine patterns of taxonomic and phylogenetic relatedness between native and nonnative taxa across thousands of nested locations ranging in size and extent, from local to regional scales. We find that the probability of observing the signature of environmental filtering over that of competition increases with spatial scale. Further, native and nonnative species tended to be less related in warm, humid environments. Our work provides an empirical assessment of the role of observation scale and climate in biological invasions and demonstrates that Darwin's two opposing hypotheses need not be mutually exclusive.
- Aguirre-Gutiérrez, J., Oliveras, I., Rifai, S., Fauset, S., Adu-Bredu, S., Affum-Baffoe, K., Baker, T. R., Feldpausch, T. R., Gvozdevaite, A., Hubau, W., Kraft, N. J., Lewis, S. L., Moore, S., Niinemets, ., Peprah, T., Phillips, O. L., Ziemińska, K., Enquist, B., & Malhi, Y. (2019). Drier tropical forests are susceptible to functional changes in response to a long-term drought. Ecology letters, 22(5), 855-865.More infoClimatic changes have profound effects on the distribution of biodiversity, but untangling the links between climatic change and ecosystem functioning is challenging, particularly in high diversity systems such as tropical forests. Tropical forests may also show different responses to a changing climate, with baseline climatic conditions potentially inducing differences in the strength and timing of responses to droughts. Trait-based approaches provide an opportunity to link functional composition, ecosystem function and environmental changes. We demonstrate the power of such approaches by presenting a novel analysis of long-term responses of different tropical forest to climatic changes along a rainfall gradient. We explore how key ecosystem's biogeochemical properties have shifted over time as a consequence of multi-decadal drying. Notably, we find that drier tropical forests have increased their deciduous species abundance and generally changed more functionally than forests growing in wetter conditions, suggesting an enhanced ability to adapt ecologically to a drying environment.
- Bruelheide, H., Dengler, J., Jimenez-Alfaro, B., Purschke, O., Hennekens, S. M., Chytry, M., Pillar, V. D., Jansen, F., Kattge, J., Sandel, B., Aubin, I., Biurrun, I., Field, R., Haider, S., Jandt, U., Lenoir, J., Peet, R. K., Peyre, G., Sabatini, F. M., , Schmidt, M., et al. (2019). sPlot - A new tool for global vegetation analyses. JOURNAL OF VEGETATION SCIENCE, 30(2), 161-186.
- Buzzard, V., Michaletz, S. T., Deng, Y., He, Z., Ning, D., Shen, L., Tu, Q., Van Nostrand, J. D., Voordeckers, J. W., Wang, J., Weiser, M. D., Kaspari, M., Waide, R. B., Zhou, J., & Enquist, B. J. (2019). Author Correction: Continental scale structuring of forest and soil diversity via functional traits. Nature ecology & evolution, 3(11), 1607.More infoAn amendment to this paper has been published and can be accessed via a link at the top of the paper.
- Buzzard, V., Michaletz, S. T., Deng, Y., He, Z., Ning, D., Shen, L., Tu, Q., Van Nostrand, J. D., Voordeckers, J. W., Wang, J., Weiser, M. D., Kaspari, M., Waide, R. B., Zhou, J., & Enquist, B. J. (2019). Continental scale structuring of forest and soil diversity via functional traits. Nature ecology & evolution, 3(9), 1298-1308.More infoTrait-based ecology claims to offer a mechanistic approach for explaining the drivers that structure biological diversity and predicting the responses of species, trophic interactions and ecosystems to environmental change. However, support for this claim is lacking across broad taxonomic groups. A framework for defining ecosystem processes in terms of the functional traits of their constituent taxa across large spatial scales is needed. Here, we provide a comprehensive assessment of the linkages between climate, plant traits and soil microbial traits at many sites spanning a broad latitudinal temperature gradient from tropical to subalpine forests. Our results show that temperature drives coordinated shifts in most plant and soil bacterial traits but these relationships are not observed for most fungal traits. Shifts in plant traits are mechanistically associated with soil bacterial functional traits related to carbon (C), nitrogen (N) and phosphorus (P) cycling, indicating that microbial processes are tightly linked to variation in plant traits that influence rates of ecosystem decomposition and nutrient cycling. Our results are consistent with hypotheses that diversity gradients reflect shifts in phenotypic optima signifying local temperature adaptation mediated by soil nutrient availability and metabolism. They underscore the importance of temperature in structuring the functional diversity of plants and soil microbes in forest ecosystems and how this is coupled to biogeochemical processes via functional traits.
- Chavana-Bryant, C., Malhi, Y., Anastasiou, A., Enquist, B. J., Cosio, E. G., Keenan, T. F., & Gerard, F. F. (2019). Leaf age effects on the spectral predictability of leaf traits in Amazonian canopy trees. The Science of the total environment, 666, 1301-1315.More infoRecent work has shown that leaf traits and spectral properties change through time and/or seasonally as leaves age. Current field and hyperspectral methods used to estimate canopy leaf traits could, therefore, be significantly biased by variation in leaf age. To explore the magnitude of this effect, we used a phenological dataset comprised of leaves of different leaf age groups -developmental, mature, senescent and mixed-age- from canopy and emergent tropical trees in southern Peru. We tested the performance of partial least squares regression models developed from these different age groups when predicting traits for leaves of different ages on both a mass and area basis. Overall, area-based models outperformed mass-based models with a striking improvement in prediction observed for area-based leaf carbon (C) estimates. We observed trait-specific age effects in all mass-based models while area-based models displayed age effects in mixed-age leaf groups for P and N. Spectral coefficients and variable importance in projection (VIPs) also reflected age effects. Both mass- and area-based models for all five leaf traits displayed age/temporal sensitivity when we tested their ability to predict the traits of leaves of other age groups. Importantly, mass-based mature models displayed the worst overall performance when predicting the traits of leaves from other age groups. These results indicate that the widely adopted approach of using fully expanded mature leaves to calibrate models that estimate remotely-sensed tree canopy traits introduces error that can bias results depending on the phenological stage of canopy leaves. To achieve temporally stable models, spectroscopic studies should consider producing area-based estimates as well as calibrating models with leaves of different age groups as they present themselves through the growing season. We discuss the implications of this for surveys of canopies with synchronised and unsynchronised leaf phenology.
- Durán, S. M., Martin, R. E., Díaz, S., Maitner, B. S., Malhi, Y., Salinas, N., Shenkin, A., Silman, M. R., Wieczynski, D. J., Asner, G. P., Bentley, L. P., Savage, V. M., & Enquist, B. J. (2019). Informing trait-based ecology by assessing remotely sensed functional diversity across a broad tropical temperature gradient. Science advances, 5(12), eaaw8114.More infoSpatially continuous data on functional diversity will improve our ability to predict global change impacts on ecosystem properties. We applied methods that combine imaging spectroscopy and foliar traits to estimate remotely sensed functional diversity in tropical forests across an Amazon-to-Andes elevation gradient (215 to 3537 m). We evaluated the scale dependency of community assembly processes and examined whether tropical forest productivity could be predicted by remotely sensed functional diversity. Functional richness of the community decreased with increasing elevation. Scale-dependent signals of trait convergence, consistent with environmental filtering, play an important role in explaining the range of trait variation within each site and along elevation. Single- and multitrait remotely sensed measures of functional diversity were important predictors of variation in rates of net and gross primary productivity. Our findings highlight the potential of remotely sensed functional diversity to inform trait-based ecology and trait diversity-ecosystem function linkages in hyperdiverse tropical forests.
- Enquist, B. J., Feng, X., Boyle, B., Maitner, B., Newman, E. A., Jørgensen, P. M., Roehrdanz, P. R., Thiers, B. M., Burger, J. R., Corlett, R. T., Couvreur, T. L., Dauby, G., Donoghue, J. C., Foden, W., Lovett, J. C., Marquet, P. A., Merow, C., Midgley, G., Morueta-Holme, N., , Neves, D. M., et al. (2019). The commonness of rarity: Global and future distribution of rarity across land plants. Science advances, 5(11), eaaz0414.More infoA key feature of life's diversity is that some species are common but many more are rare. Nonetheless, at global scales, we do not know what fraction of biodiversity consists of rare species. Here, we present the largest compilation of global plant diversity to quantify the fraction of Earth's plant biodiversity that are rare. A large fraction, ~36.5% of Earth's ~435,000 plant species, are exceedingly rare. Sampling biases and prominent models, such as neutral theory and the k-niche model, cannot account for the observed prevalence of rarity. Our results indicate that (i) climatically more stable regions have harbored rare species and hence a large fraction of Earth's plant species via reduced extinction risk but that (ii) climate change and human land use are now disproportionately impacting rare species. Estimates of global species abundance distributions have important implications for risk assessments and conservation planning in this era of rapid global change.
- Martin, R. E., Asner, G. P., Bentley, L. P., Shenkin, A., Salinas, N., Huaypar, K. Q., Pillco, M. M., Ccori Álvarez, F. D., Enquist, B. J., Diaz, S., & Malhi, Y. (2019). Covariance of Sun and Shade Leaf Traits Along a Tropical Forest Elevation Gradient. Frontiers in plant science, 10, 1810.More infoFoliar trait adaptation to sun and shade has been extensively studied in the context of photosynthetic performance of plants, focusing on nitrogen allocation, light capture and use chlorophyll pigments and leaf morphology; however, less is known about the potential sun-shade dichotomy of other functionally important foliar traits. In this study, we measured 19 traits in paired sun and shade leaves along a 3,500-m elevation gradient in southern Peru to test whether the traits differ with canopy position, and to assess if relative differences vary with species composition and/or environmental filters. We found significant sun-shade differences in leaf mass per area (LMA), photosynthetic pigments (Chl ab and Car), and δC. Sun-shade offsets among these traits remained constant with elevation, soil substrates, and species compositional changes. However, other foliar traits related to structure and chemical defense, and those defining general metabolic processes, did not differ with canopy position. Our results suggest that whole-canopy function is captured in many traits of sun leaves; however, photosynthesis-related traits must be scaled based on canopy light extinction. These findings show that top-of-canopy measurements of foliar chemistry from spectral remote sensing approaches map directly to whole-canopy foliar traits including shaded leaves that cannot be directly observed from above.
- McFadden, I. R., Sandel, B., Tsirogiannis, C., Morueta-Holme, N., Svenning, J. C., Enquist, B. J., & Kraft, N. J. (2019). Temperature shapes opposing latitudinal gradients of plant taxonomic and phylogenetic β diversity. Ecology letters, 22(7), 1126-1135.More infoLatitudinal and elevational richness gradients have received much attention from ecologists but there is little consensus on underlying causes. One possible proximate cause is increased levels of species turnover, or β diversity, in the tropics compared to temperate regions. Here, we leverage a large botanical dataset to map taxonomic and phylogenetic β diversity, as mean turnover between neighboring 100 × 100 km cells, across the Americas and determine key climatic drivers. We find taxonomic and tip-weighted phylogenetic β diversity is higher in the tropics, but that basal-weighted phylogenetic β diversity is highest in temperate regions. Supporting Janzen's 'mountain passes' hypothesis, tropical mountainous regions had higher β diversity than temperate regions for taxonomic and tip-weighted metrics. The strongest climatic predictors of turnover were average temperature and temperature seasonality. Taken together, these results suggest β diversity is coupled to latitudinal richness gradients and that temperature is a major driver of plant community composition and change.
- Steidinger, B. S., Crowther, T. W., Liang, J., Van Nuland, M. E., Werner, G. D., Reich, P. B., Nabuurs, G. J., de-Miguel, S., Zhou, M., Picard, N., Herault, B., Zhao, X., Zhang, C., Routh, D., Peay, K. G., & , G. c. (2019). Author Correction: Climatic controls of decomposition drive the global biogeography of forest-tree symbioses. Nature, 571(7765), E8.More infoIn this Letter, a middle initial and additional affiliation have been added for author G. J. Nabuurs; two statements have been added to the Supplementary Acknowledgements; and a citation to the French National Institute has been added to the Methods; see accompanying Author Correction for further details.
- Steidinger, B. S., Crowther, T. W., Liang, J., Van Nuland, M. E., Werner, G. D., Reich, P. B., Nabuurs, G. J., de-Miguel, S., Zhou, M., Picard, N., Herault, B., Zhao, X., Zhang, C., Routh, D., Peay, K. G., & , G. c. (2019). Climatic controls of decomposition drive the global biogeography of forest-tree symbioses. Nature, 569(7756), 404-408.More infoThe identity of the dominant root-associated microbial symbionts in a forest determines the ability of trees to access limiting nutrients from atmospheric or soil pools, sequester carbon and withstand the effects of climate change. Characterizing the global distribution of these symbioses and identifying the factors that control this distribution are thus integral to understanding the present and future functioning of forest ecosystems. Here we generate a spatially explicit global map of the symbiotic status of forests, using a database of over 1.1 million forest inventory plots that collectively contain over 28,000 tree species. Our analyses indicate that climate variables-in particular, climatically controlled variation in the rate of decomposition-are the primary drivers of the global distribution of major symbioses. We estimate that ectomycorrhizal trees, which represent only 2% of all plant species, constitute approximately 60% of tree stems on Earth. Ectomycorrhizal symbiosis dominates forests in which seasonally cold and dry climates inhibit decomposition, and is the predominant form of symbiosis at high latitudes and elevation. By contrast, arbuscular mycorrhizal trees dominate in aseasonal, warm tropical forests, and occur with ectomycorrhizal trees in temperate biomes in which seasonally warm-and-wet climates enhance decomposition. Continental transitions between forests dominated by ectomycorrhizal or arbuscular mycorrhizal trees occur relatively abruptly along climate-driven decomposition gradients; these transitions are probably caused by positive feedback effects between plants and microorganisms. Symbiotic nitrogen fixers-which are insensitive to climatic controls on decomposition (compared with mycorrhizal fungi)-are most abundant in arid biomes with alkaline soils and high maximum temperatures. The climatically driven global symbiosis gradient that we document provides a spatially explicit quantitative understanding of microbial symbioses at the global scale, and demonstrates the critical role of microbial mutualisms in shaping the distribution of plant species.
- Steidinger, B. S., Crowther, T. W., Liang, J., Van, N., Werner, G., Reich, P. B., Nabuurs, G., de-Miguel, S., Zhou, M., Picard, N., Herault, B., Zhao, X., Zhang, C., Routh, D., Peay, K. G., Abegg, M., Yao, C., Alberti, G., Zambrano, A. A., , Alvarez-Davila, E., et al. (2019). Climatic controls of decomposition drive the global biogeography of forest-tree symbioses. NATURE, 569(7756), 404-+.
- Wieczynski, D. J., Wieczynski, D. J., Boyle, B., Boyle, B., Buzzard, V., Buzzard, V., Duran, S. M., Duran, S. M., Henderson, A. N., Henderson, A. N., Hulshof, C. M., Hulshof, C. M., Kerkhoff, A. J., Kerkhoff, A. J., McCarthy, M. C., McCarthy, M. C., Michaletz, S. T., Michaletz, S. T., Swenson, N. G., , Swenson, N. G., et al. (2019). Climate shapes and shifts functional biodiversity in forests worldwide. Proceedings of the National Academy of Sciences of the United States of America, 116(2), 587-592.More infoMuch ecological research aims to explain how climate impacts biodiversity and ecosystem-level processes through functional traits that link environment with individual performance. However, the specific climatic drivers of functional diversity across space and time remain unclear due largely to limitations in the availability of paired trait and climate data. We compile and analyze a global forest dataset using a method based on abundance-weighted trait moments to assess how climate influences the shapes of whole-community trait distributions. Our approach combines abundance-weighted metrics with diverse climate factors to produce a comprehensive catalog of trait-climate relationships that differ dramatically-27% of significant results change in sign and 71% disagree on sign, significance, or both-from traditional species-weighted methods. We find that () functional diversity generally declines with increasing latitude and elevation, () temperature variability and vapor pressure are the strongest drivers of geographic shifts in functional composition and ecological strategies, and () functional composition may currently be shifting over time due to rapid climate warming. Our analysis demonstrates that climate strongly governs functional diversity and provides essential information needed to predict how biodiversity and ecosystem function will respond to climate change.
- Babst, F., Babst, F., Bodesheim, P., Bodesheim, P., Charney, N., Charney, N., Friend, A., Friend, A., Girardin, M., Girardin, M., Klesse, S., Klesse, S., Moore, D. J., Moore, D. J., Seftigen, K., Seftigen, K., Bjorklund, J., Bjorklund, J., Bouriaud, O., , Bouriaud, O., et al. (2018). When tree rings go global: challenges and opportunities for retro- and prospective insight. Quarternary Science Reviews, 197, 1-20. doi:https://doi.org/10.1016/j.quascirev.2018.07.009
- Babst, F., Bodesheim, P., Charney, N., Friend, A. D., Girardin, M. P., Klesse, S., Moore, D., Seftigen, K., Bjorklund, J., Bouriaud, O., Dawson, A., DeRose, R. J., Dietze, M. C., Eckes, A. H., Enquist, B., Frank, D. C., Mahecha, M. D., Poulter, B., Record, S., , Trouet, V., et al. (2018). When tree rings go global: Challenges and opportunities for retro- and prospective insight. QUATERNARY SCIENCE REVIEWS, 197, 1-20.
- Bjorkman, A. D., Myers-Smith, I. H., Elmendorf, S. C., Normand, S., Rueger, N., Beck, P., Blach-Overgaard, A., Blok, D., Cornelissen, J., Forbes, B. C., Georges, D., Goetz, S. J., Guay, K. C., Henry, G., HilleRisLambers, J., Hollister, R. D., Karger, D. N., Kattge, J., Manning, P., , Prevey, J. S., et al. (2018). Plant functional trait change across a warming tundra biome. NATURE, 562(7725), 57-+.
- Bjorkman, A. D., Myers-Smith, I. H., Elmendorf, S. C., Normand, S., Rüger, N., Beck, P. S., Blach-Overgaard, A., Blok, D., Cornelissen, J. H., Forbes, B. C., Georges, D., Goetz, S. J., Guay, K. C., Henry, G. H., HilleRisLambers, J., Hollister, R. D., Karger, D. N., Kattge, J., Manning, P., , Prevéy, J. S., et al. (2018). Plant functional trait change across a warming tundra biome. Nature, 562(7725), 57-62.More infoThe tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.
- Blonder, B., Enquist, B. J., Graae, B. J., Kattge, J., Maitner, B. S., Morueta-Holme, N., Ordonez, A., Šímová, I., Singarayer, J., Svenning, J. C., Valdes, P. J., & Violle, C. (2018). Late Quaternary climate legacies in contemporary plant functional composition. Global change biology, 24(10), 4827-4840.More infoThe functional composition of plant communities is commonly thought to be determined by contemporary climate. However, if rates of climate-driven immigration and/or exclusion of species are slow, then contemporary functional composition may be explained by paleoclimate as well as by contemporary climate. We tested this idea by coupling contemporary maps of plant functional trait composition across North and South America to paleoclimate means and temporal variation in temperature and precipitation from the Last Interglacial (120 ka) to the present. Paleoclimate predictors strongly improved prediction of contemporary functional composition compared to contemporary climate predictors, with a stronger influence of temperature in North America (especially during periods of ice melting) and of precipitation in South America (across all times). Thus, climate from tens of thousands of years ago influences contemporary functional composition via slow assemblage dynamics.
- Blonder, B., Morrow, C. B., Maitner, B., Harris, D. J., Lamanna, C., Violle, C., Enquist, B. J., & Kerkhoff, A. J. (2018). New approaches for delineating n-dimensional hypervolumes. METHODS IN ECOLOGY AND EVOLUTION, 9(2), 305-319.
- Doughty, C. E., Santos-Andrade, P. E., Shenkin, A., Goldsmith, G. R., Bentley, L. P., Blonder, B., Díaz, S., Salinas, N., Enquist, B. J., Martin, R. E., Asner, G. P., & Malhi, Y. (2018). Tropical forest leaves may darken in response to climate change. Nature ecology & evolution, 2(12), 1918-1924.More infoTropical forest leaf albedo (reflectance) greatly impacts how much energy the planet absorbs; however; little is known about how it might be impacted by climate change. Here, we measure leaf traits and leaf albedo at ten 1-ha plots along a 3,200-m elevation gradient in Peru. Leaf mass per area (LMA) decreased with warmer temperatures along the elevation gradient; the distribution of LMA was positively skewed at all sites indicating a shift in LMA towards a warmer climate and future reduced tropical LMA. Reduced LMA was significantly (P
- Eiserhardt, W. L., Antonelli, A., Bennett, D. J., Botigué, L. R., Burleigh, J. G., Dodsworth, S., Enquist, B. J., Forest, F., Kim, J. T., Kozlov, A. M., Leitch, I. J., Maitner, B. S., Mirarab, S., Piel, W. H., Pérez-Escobar, O. A., Pokorny, L., Rahbek, C., Sandel, B., Smith, S. A., , Stamatakis, A., et al. (2018). A roadmap for global synthesis of the plant tree of life. American journal of botany, 105(3), 614-622.More infoProviding science and society with an integrated, up-to-date, high quality, open, reproducible and sustainable plant tree of life would be a huge service that is now coming within reach. However, synthesizing the growing body of DNA sequence data in the public domain and disseminating the trees to a diverse audience are often not straightforward due to numerous informatics barriers. While big synthetic plant phylogenies are being built, they remain static and become quickly outdated as new data are published and tree-building methods improve. Moreover, the body of existing phylogenetic evidence is hard to navigate and access for non-experts. We propose that our community of botanists, tree builders, and informaticians should converge on a modular framework for data integration and phylogenetic analysis, allowing easy collaboration, updating, data sourcing and flexible analyses. With support from major institutions, this pipeline should be re-run at regular intervals, storing trees and their metadata long-term. Providing the trees to a diverse global audience through user-friendly front ends and application development interfaces should also be a priority. Interactive interfaces could be used to solicit user feedback and thus improve data quality and to coordinate the generation of new data. We conclude by outlining a number of steps that we suggest the scientific community should take to achieve global phylogenetic synthesis.
- Henn, J. J., Buzzard, V., Enquist, B. J., Halbritter, A. H., Klanderud, K., Maitner, B. S., Michaletz, S. T., Pötsch, C., Seltzer, L., Telford, R. J., Yang, Y., Zhang, L., & Vandvik, V. (2018). Intraspecific Trait Variation and Phenotypic Plasticity Mediate Alpine Plant Species Response to Climate Change. Frontiers in plant science, 9, 1548.More infoIn a rapidly changing climate, alpine plants may persist by adapting to new conditions. However, the rate at which the climate is changing might exceed the rate of adaptation through evolutionary processes in long-lived plants. Persistence may depend on phenotypic plasticity in morphology and physiology. Here we investigated patterns of leaf trait variation including leaf area, leaf thickness, specific leaf area, leaf dry matter content, leaf nutrients (C, N, P) and isotopes (δC and δN) across an elevation gradient on Gongga Mountain, Sichuan Province, China. We quantified inter- and intra-specific trait variation and the plasticity in leaf traits of selected species to experimental warming and cooling by using a reciprocal transplantation approach. We found substantial phenotypic plasticity in most functional traits where δN, leaf area, and leaf P showed greatest plasticity. These traits did not correspond with traits with the largest amount of intraspecific variation. Plasticity in leaf functional traits tended to enable plant populations to shift their trait values toward the mean values of a transplanted plants' destination community, but only if that population started with very different trait values. These results suggest that leaf trait plasticity is an important mechanism for enabling plants to persist within communities and to better tolerate changing environmental conditions under climate change.
- Henn, J. J., Buzzard, V., Enquist, B. J., Halbritter, A. H., Klanderuds, K., Maitner, B. S., Michaletz, S. T., Potschs, C., Seltzer, L., Telford, R. J., Yang, Y., Zhang, L. i., & Vandvik, V. (2018). Intraspecific Trait Variation and Phenotypic Plasticity Mediate Alpine Plant Species Response to Climate Change. FRONTIERS IN PLANT SCIENCE, 9.
- Maitner, B. S., Boyle, B., Casler, N., Condit, R., Donoghue, J. I., Duran, S. M., Guaderrama, D., Hinchliff, C. E., Jorgensen, P. M., Kraft, N., McGill, B., Merow, C., Morueta-Holme, N., Peet, R. K., Sandel, B., Schildhauer, M., Smith, S. A., Svenning, J., Thiers, B., , Violle, C., et al. (2018). The BIEN R package: A tool to access the Botanical Information and Ecology Network (BIEN) database. METHODS IN ECOLOGY AND EVOLUTION, 9(2), 373-379.
- Messier, J., Violle, C., Enquist, B. J., Lechowicz, M. J., & McGill, B. J. (2018). Similarities and differences in intrapopulation trait correlations of co-occurring tree species: consistent water-use relationships amid widely different correlation patterns. American journal of botany, 105(9), 1477-1490.More infoGeneral relationships among functional traits have been identified across species, but the forces shaping these relationships remain largely unknown. Adopting an approach from evolutionary biology, we studied similarities and differences in intrapopulation trait correlations among locally co-occurring tree species to assess the roles of constraints, phylogeny, and the environmental niche in shaping multivariate phenotypes. We tested the hypotheses (1) that intrapopulation correlations among functional traits are largely shaped by fundamental trade-offs or constraints and (2) that differences among species reflect adaptation to their environmental niches.
- Michaletz, S. T., Kerkhoff, A. J., & Enquist, B. J. (2018). Drivers of terrestrial plant production across broad geographical gradients. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 27(2), 166-174.
- Oliveras, I., Roman-Cuesta, R. M., Urquiaga-Flores, E., Loayza, J., Kala, J., Huaman, V., Lizarraga, N., Sans, G., Quispe, K., Lopez, E., Lopez, D., Cuba, T. I., Enquist, B. J., & Malhi, Y. (2018). Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence. GLOBAL CHANGE BIOLOGY, 24(2), 758-772.
- Oliveras, I., Román-Cuesta, R. M., Urquiaga-Flores, E., Quintano Loayza, J. A., Kala, J., Huamán, V., Lizárraga, N., Sans, G., Quispe, K., Lopez, E., Lopez, D., Cuba Torres, I., Enquist, B. J., & Malhi, Y. (2018). Fire effects and ecological recovery pathways of tropical montane cloud forests along a time chronosequence. Global change biology, 24(2), 758-772.More infoTropical montane cloud forests (TMCFs) harbour high levels of biodiversity and large carbon stocks. Their location at high elevations make them especially sensitive to climate change, because a warming climate is enhancing upslope species migration, but human disturbance (especially fire) may in many cases be pushing the treeline downslope. TMCFs are increasingly being affected by fire, and the long-term effects of fire are still unknown. Here, we present a 28-year chronosequence to assess the effects of fire and recovery pathways of burned TMCFs, with a detailed analysis of carbon stocks, forest structure and diversity. We assessed rates of change of carbon (C) stock pools, forest structure and tree-size distribution pathways and tested several hypotheses regarding metabolic scaling theory (MST), C recovery and biodiversity. We found four different C stock recovery pathways depending on the selected C pool and time since last fire, with a recovery of total C stocks but not of aboveground C stocks. In terms of forest structure, there was an increase in the number of small stems in the burned forests up to 5-9 years after fire because of regeneration patterns, but no differences on larger trees between burned and unburned plots in the long term. In support of MST, after fire, forest structure appears to approximate steady-state size distribution in less than 30 years. However, our results also provide new evidence that the species recovery of TMCF after fire is idiosyncratic and follows multiple pathways. While fire increased species richness, it also enhanced species dissimilarity with geographical distance. This is the first study to report a long-term chronosequence of recovery pathways to fire suggesting faster recovery rates than previously reported, but at the expense of biodiversity and aboveground C stocks.
- Saleska, S. R., Enquist, B. J., Boyle, B., Meir, P., da Costa, A. C., Ferreira, L. V., de Camargo, P. B., Simova, I., Violle, C., Van Haren, J. L., Smith, M. N., McMahon, S. M., & Taylor, T. C. (2018). Isoprene emission structures tropical tree biogeography and community assembly responses to climate. New Phytologist.
- Simova, I., Violle, C., Svenning, J., Kattge, J., Engemann, K., Sandel, B., Peet, R. K., Wiser, S. K., Blonder, B., McGill, B. J., Boyle, B., Morueta-Holme, N., Kraft, N., van, B., Gutierrez, A. G., Bahn, M., Ozinga, W. A., Toszogyova, A., & Enquist, B. J. (2018). Spatial patterns and climate relationships of major plant traits in the New World differ between woody and herbaceous species. JOURNAL OF BIOGEOGRAPHY, 45(4), 895-916.
- Sørensen, M. V., Graae, B. J., Hagen, D., Enquist, B. J., Nystuen, K. O., & Strimbeck, R. (2018). Experimental herbivore exclusion, shrub introduction, and carbon sequestration in alpine plant communities. BMC ecology, 18(1), 29.More infoShrub cover in arctic and alpine ecosystems has increased in recent decades, and is predicted to further increase with climate change. Changes in shrub abundance may alter ecosystem carbon (C) sequestration and storage, with potential positive feedback on global C cycling. Small and large herbivores may reduce shrub expansion and thereby counteract the positive feedback on C cycling, but herbivore pressures have also changed in the alpine-arctic tundra; the increased shrub cover together with changes in herbivore pressure is leading to unpredictable changes in carbon sequestration and storage. In this study we investigate the importance of herbivory and shrub introduction for carbon sequestration in the short term. We measured standing biomass and daytime mid-growing season carbon fluxes in plots in a full factorial design where we excluded small and large mammalian herbivores and introduced Salix by planting Salix transplants. We used three study sites: one Empetrum-dominated heath, one herb- and cryptogam-dominated meadow, and one Salix-dominated shrub community in the low-alpine zone of the Dovre Mountains, Central Norway.
- Taylor, T. C., McMahon, S. M., Smith, M. N., Boyle, B., Violle, C., van Haren, J., Simova, I., Meir, P., Ferreira, L. V., de Camargo, P. B., da Costa, A. C., Enquist, B. J., & Saleska, S. R. (2018). Isoprene emission structures tropical tree biogeography and community assembly responses to climate. The New phytologist, 220(2), 435-446.More infoThe prediction of vegetation responses to climate requires a knowledge of how climate-sensitive plant traits mediate not only the responses of individual plants, but also shifts in the species and functional compositions of whole communities. The emission of isoprene gas - a trait shared by one-third of tree species - is known to protect leaf biochemistry under climatic stress. Here, we test the hypothesis that isoprene emission shapes tree species compositions in tropical forests by enhancing the tolerance of emitting trees to heat and drought. Using forest inventory data, we estimated the proportional abundance of isoprene-emitting trees (pIE) at 103 lowland tropical sites. We also quantified the temporal composition shifts in three tropical forests - two natural and one artificial - subjected to either anomalous warming or drought. Across the landscape, pIE increased with site mean annual temperature, but decreased with dry season length. Through time, pIE strongly increased under high temperatures, and moderately increased following drought. Our analysis shows that isoprene emission is a key plant trait determining species responses to climate. For species adapted to seasonal dry periods, isoprene emission may tradeoff with alternative strategies, such as leaf deciduousness. Community selection for isoprene-emitting species is a potential mechanism for enhanced forest resilience to climatic change.
- Vasseur, F., Exposito-Alonso, M., Ayala-Garay, O. J., Wang, G., Enquist, B. J., Vile, D., Violle, C., & Weigel, D. (2018). Adaptive diversification of growth allometry in the plant Arabidopsis thaliana. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 115(13), 3416-3421.
- Vasseur, F., Exposito-Alonso, M., Ayala-Garay, O. J., Wang, G., Enquist, B. J., Vile, D., Violle, C., & Weigel, D. (2018). Adaptive diversification of growth allometry in the plant. Proceedings of the National Academy of Sciences of the United States of America.More infoSeed plants vary tremendously in size and morphology; however, variation and covariation in plant traits may be governed, at least in part, by universal biophysical laws and biological constants. Metabolic scaling theory (MST) posits that whole-organismal metabolism and growth rate are under stabilizing selection that minimizes the scaling of hydrodynamic resistance and maximizes the scaling of resource uptake. This constrains variation in physiological traits and in the rate of biomass accumulation, so that they can be expressed as mathematical functions of plant size with near-constant allometric scaling exponents across species. However, the observed variation in scaling exponents calls into question the evolutionary drivers and the universality of allometric equations. We have measured growth scaling and fitness traits of 451accessions with sequenced genomes. Variation among accessions around the scaling exponent predicted by MST was correlated with relative growth rate, seed production, and stress resistance. Genomic analyses indicate that growth allometry is affected by many genes associated with local climate and abiotic stress response. The gene with the strongest effect,, has molecular signatures of balancing selection, suggesting that intraspecific variation in growth scaling is maintained by opposing selection on the trade-off between seed production and abiotic stress resistance. Our findings suggest that variation in allometry contributes to local adaptation to contrasting environments. Our results help reconcile past debates on the origin of allometric scaling in biology and begin to link adaptive variation in allometric scaling to specific genes.
- Asner, G. P., Martin, R. E., Anderson, C. B., Kryston, K., Vaughn, N., Knapp, D. E., Bentley, L. P., Shenkin, A., Salinas, N., Sinca, F., Tupayachi, R., Huaypar, K. Q., Pillco, M. M., Alvarez, F., Diaz, S., Enquist, B. J., & Malhi, Y. (2017). Scale dependence of canopy trait distributions along a tropical forest elevation gradient. NEW PHYTOLOGIST, 214(3), 973-988.
- Blonder, B., Moulton, D. E., Blois, J., Enquist, B. J., Graae, B. J., Macias-Fauria, M., McGill, B., Nogue, S., Ordonez, A., Sandel, B., & Svenning, J. (2017). Predictability in community dynamics. ECOLOGY LETTERS, 20(3), 293-306.
- Blonder, B., Moulton, D. E., Blois, J., Enquist, B. J., Graae, B. J., Macias-Fauria, M., McGill, B., Nogué, S., Ordonez, A., Sandel, B., & Svenning, J. C. (2017). Predictability in community dynamics. Ecology letters, 20(3), 293-306.More infoThe coupling between community composition and climate change spans a gradient from no lags to strong lags. The no-lag hypothesis is the foundation of many ecophysiological models, correlative species distribution modelling and climate reconstruction approaches. Simple lag hypotheses have become prominent in disequilibrium ecology, proposing that communities track climate change following a fixed function or with a time delay. However, more complex dynamics are possible and may lead to memory effects and alternate unstable states. We develop graphical and analytic methods for assessing these scenarios and show that these dynamics can appear in even simple models. The overall implications are that (1) complex community dynamics may be common and (2) detailed knowledge of past climate change and community states will often be necessary yet sometimes insufficient to make predictions of a community's future state.
- Blonder, B., Salinas, N., Patrick Bentley, L., Shenkin, A., Chambi Porroa, P. O., Valdez Tejeira, Y., Violle, C., Fyllas, N. M., Goldsmith, G. R., Martin, R., Asner, G. P., Díaz, S., Enquist, B. J., & Malhi, Y. (2017). Predicting trait-environment relationships for venation networks along an Andes-Amazon elevation gradient. Ecology.More infoUnderstanding functional trait-environment relationships (TERs) may improve predictions of community assembly. However, many empirical TERs have been weak or lacking conceptual foundation. TERs based on leaf venation networks may better link individuals and communities via hydraulic constraints. We report measurements of vein density, vein radius, and leaf thickness for more than 100 dominant species occurring in ten forest communities spanning a 3300 m Andes-Amazon elevation gradient in Peru. We use these data to measure the strength of TERs at community scale and to determine whether observed TERs are similar to those predicted by physiological theory. We found strong support for TERs between all traits and temperature, as well weaker support for a predicted TER between maximum abundance-weighted leaf transpiration rate and maximum potential evapotranspiration. These results provide one approach for developing a more mechanistic trait-based community assembly theory. This article is protected by copyright. All rights reserved.
- Brummer, A. B., Savage, V. M., & Enquist, B. J. (2017). A general model for metabolic scaling in self-similar asymmetric networks. PLOS COMPUTATIONAL BIOLOGY, 13(3).
- Brummer, A. B., Savage, V. M., & Enquist, B. J. (2017). A general model for metabolic scaling in self-similar asymmetric networks. PLoS computational biology, 13(3), e1005394.More infoHow a particular attribute of an organism changes or scales with its body size is known as an allometry. Biological allometries, such as metabolic scaling, have been hypothesized to result from selection to maximize how vascular networks fill space yet minimize internal transport distances and resistances. The West, Brown, Enquist (WBE) model argues that these two principles (space-filling and energy minimization) are (i) general principles underlying the evolution of the diversity of biological networks across plants and animals and (ii) can be used to predict how the resulting geometry of biological networks then governs their allometric scaling. Perhaps the most central biological allometry is how metabolic rate scales with body size. A core assumption of the WBE model is that networks are symmetric with respect to their geometric properties. That is, any two given branches within the same generation in the network are assumed to have identical lengths and radii. However, biological networks are rarely if ever symmetric. An open question is: Does incorporating asymmetric branching change or influence the predictions of the WBE model? We derive a general network model that relaxes the symmetric assumption and define two classes of asymmetrically bifurcating networks. We show that asymmetric branching can be incorporated into the WBE model. This asymmetric version of the WBE model results in several theoretical predictions for the structure, physiology, and metabolism of organisms, specifically in the case for the cardiovascular system. We show how network asymmetry can now be incorporated in the many allometric scaling relationships via total network volume. Most importantly, we show that the 3/4 metabolic scaling exponent from Kleiber's Law can still be attained within many asymmetric networks.
- Chavana-Bryant, C., Malhi, Y., Wu, J., Asner, G. P., Anastasiou, A., Enquist, B. J., Cosio, C., Doughty, C. E., Saleska, S. R., Martin, R. E., & Gerard, F. F. (2017). Leaf aging of Amazonian canopy trees as revealed by spectral and physiochemical measurements. NEW PHYTOLOGIST, 214(3), 1049-1063.
- Csergo, A. M., Salguero-Gomez, R., Broennimann, O., Coutts, S. R., Guisan, A., Angert, A. L., Welk, E., Stott, I., Enquist, B. J., McGill, B., Svenning, J., Violle, C., & Buckley, Y. M. (2017). Less favourable climates constrain demographic strategies in plants. ECOLOGY LETTERS, 20(8), 969-980.
- Csergő, A. M., Salguero-Gómez, R., Broennimann, O., Coutts, S. R., Guisan, A., Angert, A. L., Welk, E., Stott, I., Enquist, B. J., McGill, B., Svenning, J. C., Violle, C., & Buckley, Y. M. (2017). Less favourable climates constrain demographic strategies in plants. Ecology letters, 20(8), 969-980.More infoCorrelative species distribution models are based on the observed relationship between species' occurrence and macroclimate or other environmental variables. In climates predicted less favourable populations are expected to decline, and in favourable climates they are expected to persist. However, little comparative empirical support exists for a relationship between predicted climate suitability and population performance. We found that the performance of 93 populations of 34 plant species worldwide - as measured by in situ population growth rate, its temporal variation and extinction risk - was not correlated with climate suitability. However, correlations of demographic processes underpinning population performance with climate suitability indicated both resistance and vulnerability pathways of population responses to climate: in less suitable climates, plants experienced greater retrogression (resistance pathway) and greater variability in some demographic rates (vulnerability pathway). While a range of demographic strategies occur within species' climatic niches, demographic strategies are more constrained in climates predicted to be less suitable.
- Fyllas, N. M., Bentley, L. P., Shenkin, A., Asner, G. P., Atkin, O. K., Diaz, S., Enquist, B. J., Farfan-Rios, W., Gloor, E., Guerrieri, R., Huaraca, H. W., Ishida, Y., Martin, R. E., Meir, P., Phillips, O., Salinas, N., Silman, M., Weerasinghe, L. K., Zaragoza-Castells, J., & Malhi, Y. (2017). Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient. ECOLOGY LETTERS, 20(6), 730-740.
- Fyllas, N. M., Bentley, L. P., Shenkin, A., Asner, G. P., Atkin, O. K., Díaz, S., Enquist, B. J., Farfan-Rios, W., Gloor, E., Guerrieri, R., Huasco, W. H., Ishida, Y., Martin, R. E., Meir, P., Phillips, O., Salinas, N., Silman, M., Weerasinghe, L. K., Zaragoza-Castells, J., & Malhi, Y. (2017). Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient. Ecology letters, 20(6), 730-740.More infoOne of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait-spectra and individual-based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon-Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi-mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.
- Gallet, R., Violle, C., Fromin, N., Jabbour-Zahab, R., Enquist, B. J., & Lenormand, T. (2017). The evolution of bacterial cell size: the internal diffusion-constraint hypothesis. The ISME journal.More infoSize is one of the most important biological traits influencing organismal ecology and evolution. However, we know little about the drivers of body size evolution in unicellulars. A long-term evolution experiment (Lenski's LTEE) in which Escherichia coli adapts to a simple glucose medium has shown that not only the growth rate and the fitness of the bacterium increase over time but also its cell size. This increase in size contradicts prominent 'external diffusion' theory (EDC) predicting that cell size should have evolved toward smaller cells. Among several scenarios, we propose and test an alternative 'internal diffusion-constraint' (IDC) hypothesis for cell size evolution. A change in cell volume affects metabolite concentrations in the cytoplasm. The IDC states that a higher metabolism can be achieved by a reduction in the molecular traffic time inside of the cell, by increasing its volume. To test this hypothesis, we studied a population from the LTEE. We show that bigger cells with greater growth and CO2 production rates and lower mass-to-volume ratio were selected over time in the LTEE. These results are consistent with the IDC hypothesis. This novel hypothesis offers a promising approach for understanding the evolutionary constraints on cell size.The ISME Journal advance online publication, 4 April 2017; doi:10.1038/ismej.2017.35.
- Garnier, E., Stahl, U., Laporte, M., Kattge, J., Mougenot, I., Kuehn, I., Laporte, B., Amiaud, B., Ahrestani, F. S., Boenisch, G., Bunker, D. E., Cornelissen, J., Diaz, S., Enquist, B. J., Gachet, S., Jaureguiberry, P., Kleyer, M., Lavorel, S., Maicher, L., , Perez-Harguindeguy, N., et al. (2017). Towards a thesaurus of plant characteristics: an ecological contribution. JOURNAL OF ECOLOGY, 105(2), 298-309.
- Goldsmith, G. R., Bentley, L. P., Shenkin, A., Salinas, N., Blonder, B., Martin, R. E., Castro-Ccossco, R., Chambi-Porroa, P., Diaz, S., Enquist, B. J., Asner, G. P., & Malhi, Y. (2017). Variation in leaf wettability traits along a tropical montane elevation gradient. NEW PHYTOLOGIST, 214(3), 989-1001.
- Kaspari, M., Bujan, J., Weiser, M. D., Ning, D., Michaletz, S. T., Zhili, H., Enquist, B. J., Waide, R. B., Zhou, J., Turner, B. L., & Wright, S. J. (2017). Biogeochemistry drives diversity in the prokaryotes, fungi, and invertebrates of a Panama forest. Ecology, 98(8), 2019-2028.More infoHumans are both fertilizing the world and depleting its soils, decreasing the diversity of aquatic ecosystems and terrestrial plants in the process. We know less about how nutrients shape the abundance and diversity of the prokaryotes, fungi, and invertebrates of Earth's soils. Here we explore this question in the soils of a Panama forest subject to a 13-yr fertilization with factorial combinations of nitrogen (N), phosphorus (P), and potassium (K) and a separate micronutrient cocktail. We contrast three hypotheses linking biogeochemistry to abundance and diversity. Consistent with the Stress Hypothesis, adding N suppressed the abundance of invertebrates and the richness of all three groups of organisms by ca. 1 SD or more below controls. Nitrogen addition plots were 0.8 pH units more acidic with 18% more exchangeable aluminum, which is toxic to both prokaryotes and eukaryotes. These stress effects were frequently reversed, however, when N was added with P (for prokaryotes and invertebrates) and with added K (for fungi). Consistent with the Abundance Hypothesis, adding P generally increased prokaryote and invertebrate diversity, and adding K enhanced invertebrate diversity. Also consistent with the Abundance Hypothesis, increases in invertebrate abundance generated increases in richness. We found little evidence for the Competition Hypothesis: that single nutrients suppressed diversity by favoring a subset of high nutrient specialists, and that nutrient combinations suppressed diversity even more. Instead, combinations of nutrients, and especially the cation/micronutrient treatment, yielded the largest increases in richness in the two eukaryote groups. In sum, changes in soil biogeochemistry revealed a diversity of responses among the three dominant soil groups, positive synergies among nutrients, and-in contrast with terrestrial plants-the frequent enhancement of soil biodiversity.
- Messier, J., Lechowicz, M. J., McGill, B. J., Violle, C., & Enquist, B. J. (2017). Interspecific integration of trait dimensions at local scales: the plant phenotype as an integrated network. JOURNAL OF ECOLOGY, 105(6), 1775-1790.
- Messier, J., McGill, B. J., Enquist, B. J., & Lechowicz, M. J. (2017). Trait variation and integration across scales: is the leaf economic spectrum present at local scales?. ECOGRAPHY, 40(6), 685-697.
- Poorter, L., van, d., Arets, E., Ascarrunz, N., Enquist, B., Finegan, B., Licona, J. C., Martinez-Ramos, M., Mazzei, L., Meave, J. A., Munoz, R., Nytch, C. J., de, O., Perez-Garcia, E. A., Prado-Junior, J., Rodriguez-Velazques, J., Ruschel, A. R., Salgado-Negret, B., Schiavini, I., , Swenson, N. G., et al. (2017). Biodiversity and climate determine the functioning of Neotropical forests. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 26(12), 1423-1434.
- Stark, J., Lehman, R., Crawford, L., Enquist, B. J., & Blonder, B. (2017). Does environmental heterogeneity drive functional trait variation? A test in montane and alpine meadows. OIKOS, 126(11), 1650-1659.
- Zhou, J., Deng, Y., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Van Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2017). Correspondence: Reply to 'Analytical flaws in a continental-scale forest soil microbial diversity study'. Nature communications, 8, 15583.
- Asner, G. P., Martin, R. E., Anderson, C. B., Kryston, K., Vaughn, N., Knapp, D. E., Bentley, L. P., Shenkin, A., Salinas, N., Sinca, F., Tupayachi, R., Quispe Huaypar, K., Montoya Pillco, M., Ccori Álvarez, F. D., Díaz, S., Enquist, B., & Malhi, Y. (2016). Scale dependence of canopy trait distributions along a tropical forest elevation gradient. The New phytologist.More infoAverage responses of forest foliar traits to elevation are well understood, but far less is known about trait distributional responses to elevation at multiple ecological scales. This limits our understanding of the ecological scales at which trait variation occurs in response to environmental drivers and change. We analyzed and compared multiple canopy foliar trait distributions using field sampling and airborne imaging spectroscopy along an Andes-to-Amazon elevation gradient. Field-estimated traits were generated from three community-weighting methods, and remotely sensed estimates of traits were made at three scales defined by sampling grain size and ecological extent. Field and remote sensing approaches revealed increases in average leaf mass per unit area (LMA), water, nonstructural carbohydrates (NSCs) and polyphenols with increasing elevation. Foliar nutrients and photosynthetic pigments displayed little to no elevation trend. Sample weighting approaches had little impact on field-estimated trait responses to elevation. Plot representativeness of trait distributions at landscape scales decreased with increasing elevation. Remote sensing indicated elevation-dependent increases in trait variance and distributional skew. Multiscale invariance of LMA, leaf water and NSC mark these traits as candidates for tracking forest responses to changing climate. Trait-based ecological studies can be greatly enhanced with multiscale studies made possible by imaging spectroscopy.
- Blonder, B., Baldwin, B. G., Enquist, B. J., & Robichaux, R. H. (2016). Variation and macroevolution in leaf functional traits in the Hawaiian silversword alliance (Asteraceae). JOURNAL OF ECOLOGY, 104(1), 219-228.
- Buzzard, V., Hulshof, C. M., Birt, T., Violle, C., & Enquist, B. J. (2016). Re-growing a tropical dry forest: functional plant trait composition and community assembly during succession. FUNCTIONAL ECOLOGY, 30(6), 1006-1013.
- Carey, J. C., Tang, J., Templer, P. H., Kroeger, K. D., Crowther, T. W., Burton, A. J., Dukes, J. S., Emmett, B., Frey, S. D., Heskel, M. A., Jiang, L., Machmuller, M. B., Mohan, J., Panetta, A. M., Reich, P. B., Reinsch, S., Wang, X., Allison, S. D., Bamminger, C., , Bridgham, S., et al. (2016). Temperature response of soil respiration largely unaltered with experimental warming. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 113(48), 13797-13802.
- Carey, J. C., Tang, J., Templer, P. H., Kroeger, K. D., Crowther, T. W., Burton, A. J., Dukes, J. S., Emmett, B., Frey, S. D., Heskel, M. A., Jiang, L., Machmuller, M. B., Mohan, J., Panetta, A. M., Reich, P. B., Reinsch, S., Wang, X., Allison, S. D., Bamminger, C., , Bridgham, S., et al. (2016). Temperature response of soil respiration largely unaltered with experimental warming. Proceedings of the National Academy of Sciences of the United States of America, 113(48), 13797-13802.More infoThe respiratory release of carbon dioxide (CO2) from soil is a major yet poorly understood flux in the global carbon cycle. Climatic warming is hypothesized to increase rates of soil respiration, potentially fueling further increases in global temperatures. However, despite considerable scientific attention in recent decades, the overall response of soil respiration to anticipated climatic warming remains unclear. We synthesize the largest global dataset to date of soil respiration, moisture, and temperature measurements, totaling >3,800 observations representing 27 temperature manipulation studies, spanning nine biomes and over 2 decades of warming. Our analysis reveals no significant differences in the temperature sensitivity of soil respiration between control and warmed plots in all biomes, with the exception of deserts and boreal forests. Thus, our data provide limited evidence of acclimation of soil respiration to experimental warming in several major biome types, contrary to the results from multiple single-site studies. Moreover, across all nondesert biomes, respiration rates with and without experimental warming follow a Gaussian response, increasing with soil temperature up to a threshold of ∼25 °C, above which respiration rates decrease with further increases in temperature. This consistent decrease in temperature sensitivity at higher temperatures demonstrates that rising global temperatures may result in regionally variable responses in soil respiration, with colder climates being considerably more responsive to increased ambient temperatures compared with warmer regions. Our analysis adds a unique cross-biome perspective on the temperature response of soil respiration, information critical to improving our mechanistic understanding of how soil carbon dynamics change with climatic warming.
- Charney, N. D., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. (2016). Observed forest sensitivity to climate implies large changes in 21st century North American forest growth. ECOLOGY LETTERS, 19(9), 1119-1128.
- Charney, N. D., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. E. (2016). Observed forest sensitivity to climate implies large changes in 21st century North American forest growth. Ecology letters, 19(9), 1119-28.More infoPredicting long-term trends in forest growth requires accurate characterisation of how the relationship between forest productivity and climatic stress varies across climatic regimes. Using a network of over two million tree-ring observations spanning North America and a space-for-time substitution methodology, we forecast climate impacts on future forest growth. We explored differing scenarios of increased water-use efficiency (WUE) due to CO2 -fertilisation, which we simulated as increased effective precipitation. In our forecasts: (1) climate change negatively impacted forest growth rates in the interior west and positively impacted forest growth along the western, southeastern and northeastern coasts; (2) shifting climate sensitivities offset positive effects of warming on high-latitude forests, leaving no evidence for continued 'boreal greening'; and (3) it took a 72% WUE enhancement to compensate for continentally averaged growth declines under RCP 8.5. Our results highlight the importance of locally adapted forest management strategies to handle regional differences in growth responses to climate change.
- Charney, N., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D. C., Enquist, B. J., & Evans, M. E. (2016). Observed forest sensitivity to climate implies larger reductions in 21st century forest growth. Ecology Letters.
- Chavana-Bryant, C., Malhi, Y., Wu, J., Asner, G. P., Anastasiou, A., Enquist, B. J., Cosio Caravasi, E. G., Doughty, C. E., Saleska, S. R., Martin, R. E., & Gerard, F. F. (2016). Leaf aging of Amazonian canopy trees as revealed by spectral and physiochemical measurements. The New phytologist.More infoLeaf aging is a fundamental driver of changes in leaf traits, thereby regulating ecosystem processes and remotely sensed canopy dynamics. We explore leaf reflectance as a tool to monitor leaf age and develop a spectra-based partial least squares regression (PLSR) model to predict age using data from a phenological study of 1099 leaves from 12 lowland Amazonian canopy trees in southern Peru. Results demonstrated monotonic decreases in leaf water (LWC) and phosphorus (Pmass ) contents and an increase in leaf mass per unit area (LMA) with age across trees; leaf nitrogen (Nmass ) and carbon (Cmass ) contents showed monotonic but tree-specific age responses. We observed large age-related variation in leaf spectra across trees. A spectra-based model was more accurate in predicting leaf age (R(2) = 0.86; percent root mean square error (%RMSE) = 33) compared with trait-based models using single (R(2) = 0.07-0.73; %RMSE = 7-38) and multiple (R(2) = 0.76; %RMSE = 28) predictors. Spectra- and trait-based models established a physiochemical basis for the spectral age model. Vegetation indices (VIs) including the normalized difference vegetation index (NDVI), enhanced vegetation index 2 (EVI2), normalized difference water index (NDWI) and photosynthetic reflectance index (PRI) were all age-dependent. This study highlights the importance of leaf age as a mediator of leaf traits, provides evidence of age-related leaf reflectance changes that have important impacts on VIs used to monitor canopy dynamics and productivity and proposes a new approach to predicting and monitoring leaf age with important implications for remote sensing.
- Doughty, C. E., Wolf, A., Morueta-Holme, N., Jorgensen, P. M., Sandel, B., Violle, C., Boyle, B., Kraft, N., Peet, R. K., Enquist, B. J., Svenning, J., Blake, S., & Galetti, M. (2016). Megafauna extinction, tree species range reduction, and carbon storage in Amazonian forests. ECOGRAPHY, 39(2), 194-203.
- Engemann, K., Sandel, B., Boyle, B., Enquist, B. J., Jørgensen, P. M., Kattge, J., McGill, B. J., Morueta-Holme, N., Peet, R. K., Spencer, N. J., Violle, C., Wiser, S. K., & Svenning, J. C. (2016). A plant growth form dataset for the New World. Ecology, 97(11), 3243.More infoThis dataset provides growth form classifications for 67,413 vascular plant species from North, Central, and South America. The data used to determine growth form were compiled from five major integrated sources and two original publications: the Botanical Information and Ecology Network (BIEN), the Plant Trait Database (TRY), the SALVIAS database, the USDA PLANTS database, Missouri Botanical Garden's Tropicos database, Wright (2010), and Boyle (1996). We defined nine plant growth forms based on woodiness (woody or non-woody), shoot structure (self-supporting or not self-supporting), and root traits (rooted in soil, not rooted in soil, parasitic or aquatic): Epiphyte, Liana, Vine, Herb, Shrub, Tree, Parasite, or Aquatic. Species with multiple growth form classifications were assigned the growth form classification agreed upon by the majority (>2/3) of sources. Species with ambiguous or otherwise not interpretable growth form assignments were excluded from the final dataset but are made available with the original data. Comparisons with independent estimates of species richness for the Western hemisphere suggest that our final dataset includes the majority of New World vascular plant species. Coverage is likely more complete for temperate than for tropical species. In addition, aquatic species are likely under-represented. Nonetheless, this dataset represents the largest compilation of plant growth forms published to date, and should contribute to new insights across a broad range of research in systematics, ecology, biogeography, conservation, and global change science.
- Engemann, K., Sandel, B., Enquist, B. J., Jorgensen, P. M., Kraft, N., Marcuse-Kubitza, A., McGill, B., Morueta-Holme, N., Peet, R. K., Violle, C., Wiser, S., & Svenning, J. (2016). Patterns and drivers of plant functional group dominance across the Western Hemisphere: a macroecological re-assessment based on a massive botanical dataset. BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, 180(2), 141-160.
- Evans, M. E., Merow, C., Record, S., McMahon, S., & Enquist, B. J. (2016). Making process-based range forecasts for many species. Trends in Ecology and Evolution, 31(11), 860-871. doi:http://dx.doi.org/10.1016/j.tree.2016.08.005
- Evans, M., Merow, C., Record, S., McMahon, S. M., & Enquist, B. J. (2016). Towards Process-based Range Modeling of Many Species. TRENDS IN ECOLOGY & EVOLUTION, 31(11), 860-871.
- Feakins, S. J., Bentley, L. P., Salinas, N., Shenkin, A., Blonder, B., Goldsmith, G. R., Ponton, C., Arvin, L. J., Wu, M. S., Peters, T., West, A. J., Martin, R. E., Enquist, B. J., Asner, G. P., & Malhi, Y. (2016). Plant leaf wax biomarkers capture gradients in hydrogen isotopes of precipitation from the Andes and Amazon. GEOCHIMICA ET COSMOCHIMICA ACTA, 182, 155-172.
- Feakins, S. J., Peters, T., Wu, M. S., Shenkin, A., Salinas, N., Girardin, C., Bentley, L. P., Blonder, B., Enquist, B. J., Martin, R. E., Asner, G. P., & Malhi, Y. (2016). Production of leaf wax n-alkanes across a tropical forest elevation transect. ORGANIC GEOCHEMISTRY, 100, 89-100.
- Goldsmith, G. R., Bentley, L. P., Shenkin, A., Salinas, N., Blonder, B., Martin, R. E., Castro-Ccossco, R., Chambi-Porroa, P., Diaz, S., Enquist, B. J., Asner, G. P., & Malhi, Y. (2016). Variation in leaf wettability traits along a tropical montane elevation gradient. The New phytologist.More infoLeaf wetting is often considered to have negative effects on plant function, such that wet environments may select for leaves with certain leaf surface, morphological, and architectural traits that reduce leaf wettability. However, there is growing recognition that leaf wetting can have positive effects. We measured variation in two traits, leaf drip tips and leaf water repellency, in a series of nine tropical forest communities occurring along a 3300-m elevation gradient in southern Peru. To extend this climatic gradient, we also assembled published leaf water repellency values from 17 additional sites. We then tested hypotheses for how these traits should vary as a function of climate. Contrary to expectations, we found that the proportion of species with drip tips did not increase with increasing precipitation. Instead, drip tips increased with increasing temperature. Moreover, leaf water repellency was very low in our sites and the global analysis indicated high repellency only in sites with low precipitation and temperatures. Our findings suggest that drip tips and repellency may not solely reflect the negative effects of wetting on plant function. Understanding the drivers of leaf wettability traits can provide insight into the effects of leaf wetting on plant, community, and ecosystem function.
- Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2016). Corrigendum: Convergence of terrestrial plant production across global climate gradients. Nature, 537(7620), 432.
- Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). Corrigendum: The energetic and carbon economic origins of leaf thermoregulation. Nature plants, 2, 16147.
- Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). The energetic and carbon economic origins of leaf thermoregulation. NATURE PLANTS, 2(9).
- Michaletz, S. T., Weiser, M. D., McDowell, N. G., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2016). The energetic and carbon economic origins of leaf thermoregulation. Nature plants, 2, 16129.More infoLeaf thermoregulation has been documented in a handful of studies, but the generality and origins of this pattern are unclear. We suggest that leaf thermoregulation is widespread in both space and time, and originates from the optimization of leaf traits to maximize leaf carbon gain across and within variable environments. Here we use global data for leaf temperatures, traits and photosynthesis to evaluate predictions from a novel theory of thermoregulation that synthesizes energy budget and carbon economics theories. Our results reveal that variation in leaf temperatures and physiological performance are tightly linked to leaf traits and carbon economics. The theory, parameterized with global averaged leaf traits and microclimate, predicts a moderate level of leaf thermoregulation across a broad air temperature gradient. These predictions are supported by independent data for diverse taxa spanning a global air temperature range of ∼60 °C. Moreover, our theory predicts that net carbon assimilation can be maximized by means of a trade-off between leaf thermal stability and photosynthetic stability. This prediction is supported by globally distributed data for leaf thermal and photosynthetic traits. Our results demonstrate that the temperatures of plant tissues, and not just air, are vital to developing more accurate Earth system models.
- Morueta-Holme, N., Blonder, B., Sandel, B., McGill, B. J., Peet, R. K., Ott, J. E., Violle, C., Enquist, B. J., Jorgensen, P. M., & Svenning, J. (2016). A network approach for inferring species associations from co-occurrence data. ECOGRAPHY, 39(12), 1139-1150.
- Neyret, M., Bentley, L. P., Oliveras, I., Marimon, B. S., Marimon-Junior, B. H., Almeida de Oliveira, E., Barbosa Passos, F., Castro Ccoscco, R., Dos Santos, J., Matias Reis, S., Morandi, P. S., Rayme Paucar, G., Robles Cáceres, A., Valdez Tejeira, Y., Yllanes Choque, Y., Salinas, N., Shenkin, A., Asner, G. P., Díaz, S., , Enquist, B. J., et al. (2016). Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly. Ecology and evolution, 6(16), 5674-89.More infoUnderstanding variation in key functional traits across gradients in high diversity systems and the ecology of community changes along gradients in these systems is crucial in light of conservation and climate change. We examined inter- and intraspecific variation in leaf mass per area (LMA) of sun and shade leaves along a 3330-m elevation gradient in Peru, and in sun leaves across a forest-savanna vegetation gradient in Brazil. We also compared LMA variance ratios (T-statistics metrics) to null models to explore internal (i.e., abiotic) and environmental filtering on community structure along the gradients. Community-weighted LMA increased with decreasing forest cover in Brazil, likely due to increased light availability and water stress, and increased with elevation in Peru, consistent with the leaf economic spectrum strategy expected in colder, less productive environments. A very high species turnover was observed along both environmental gradients, and consequently, the first source of variation in LMA was species turnover. Variation in LMA at the genus or family levels was greater in Peru than in Brazil. Using dominant trees to examine possible filters on community assembly, we found that in Brazil, internal filtering was strongest in the forest, while environmental filtering was observed in the dry savanna. In Peru, internal filtering was observed along 80% of the gradient, perhaps due to variation in taxa or interspecific competition. Environmental filtering was observed at cloud zone edges and in lowlands, possibly due to water and nutrient availability, respectively. These results related to variation in LMA indicate that biodiversity in species rich tropical assemblages may be structured by differential niche-based processes. In the future, specific mechanisms generating these patterns of variation in leaf functional traits across tropical environmental gradients should be explored.
- Neyret, M., Bentley, L. P., Oliveras, I., Marimon, B. S., Marimon-Junior, B. H., de, O., Passos, F. B., Castro, C. R., dos, S. J., Reis, S. M., Morandi, P. S., Rayme, P. G., Robles, C. A., Valdez, T. Y., Yllanes, C. Y., Salinas, N., Shenkin, A., Asner, G. P., Diaz, S., , Enquist, B. J., et al. (2016). Examining variation in the leaf mass per area of dominant species across two contrasting tropical gradients in light of community assembly. ECOLOGY AND EVOLUTION, 6(16), 5674-5689.
- Tu, Q., Deng, Y. e., Yan, Q., Shen, L., Lin, L. u., He, Z., Wu, L., Van, N., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R. B., Brown, J. H., & Zhou, J. (2016). Biogeographic patterns of soil diazotrophic communities across six forests in the North America. MOLECULAR ECOLOGY, 25(12), 2937-2948.
- Tu, Q., Deng, Y., Yan, Q., Shen, L., Lin, L., He, Z., Wu, L., Van Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R. B., Brown, J. H., & Zhou, J. (2016). Biogeographic patterns of soil diazotrophic communities across six forests in the North America. Molecular ecology, 25(12), 2937-48.More infoSoil diazotrophs play important roles in ecosystem functioning by converting atmospheric N2 into biologically available ammonium. However, the diversity and distribution of soil diazotrophic communities in different forests and whether they follow biogeographic patterns similar to macroorganisms still remain unclear. By sequencing nifH gene amplicons, we surveyed the diversity, structure and biogeographic patterns of soil diazotrophic communities across six North American forests (126 nested samples). Our results showed that each forest harboured markedly different soil diazotrophic communities and that these communities followed traditional biogeographic patterns similar to plant and animal communities, including the taxa-area relationship (TAR) and latitudinal diversity gradient. Significantly higher community diversity and lower microbial spatial turnover rates (i.e. z-values) were found for rainforests (~0.06) than temperate forests (~0.1). The gradient pattern of TARs and community diversity was strongly correlated (r(2) > 0.5) with latitude, annual mean temperature, plant species richness and precipitation, and weakly correlated (r(2)
- Zhou, J., Deng, Y. e., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Van, N., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2016). Temperature mediates continental-scale diversity of microbes in forest soils. NATURE COMMUNICATIONS, 7.
- Zhou, J., Deng, Y., Shen, L., Wen, C., Yan, Q., Ning, D., Qin, Y., Xue, K., Wu, L., He, Z., Voordeckers, J. W., Nostrand, J. D., Buzzard, V., Michaletz, S. T., Enquist, B. J., Weiser, M. D., Kaspari, M., Waide, R., Yang, Y., & Brown, J. H. (2016). Temperature mediates continental-scale diversity of microbes in forest soils. Nature communications, 7, 12083.More infoClimate warming is increasingly leading to marked changes in plant and animal biodiversity, but it remains unclear how temperatures affect microbial biodiversity, particularly in terrestrial soils. Here we show that, in accordance with metabolic theory of ecology, taxonomic and phylogenetic diversity of soil bacteria, fungi and nitrogen fixers are all better predicted by variation in environmental temperature than pH. However, the rates of diversity turnover across the global temperature gradients are substantially lower than those recorded for trees and animals, suggesting that the diversity of plant, animal and soil microbial communities show differential responses to climate change. To the best of our knowledge, this is the first study demonstrating that the diversity of different microbial groups has significantly lower rates of turnover across temperature gradients than other major taxa, which has important implications for assessing the effects of human-caused changes in climate, land use and other factors.
- , B. J., , J. N., , S. P., , C. V., , C. T., , A. H., , L. L., & , V. M. (2015). Scaling from traits to ecosystems: Developing a general Trait Driver Theory via integrating trait-based and metabolic scaling theories. , Advances in Ecological Research,.More infoThe rise of trait-based ecology has led to an increased focus on thedistribution and dynamics of traits in communities. However, a general theoryof trait-based ecology, that can apply across different scales (e.g., speciesthat differ in size) and gradients (e.g., temperature), has yet to beformulated. While research focused on metabolic and allometric scaling theoryprovides the basis for such a theory it does not explicitly account fordifferences traits within and across taxa, such as variation in the optimaltemperature for growth. Here we synthesize trait-based and metabolic scalingapproaches into a framework that we term Trait Drivers Theory or TDT. It showsthat the shape and dynamics of trait distributions can be uniquely linked tofundamental drivers of community assembly and how the community will respond tofuture drivers. To assess predictions and assumptions of TDT, we review severaltheoretical studies, recent empirical studies spanning local and biogeographicgradients. Further, we analyze how the shift in trait distributions influencesecosystem productivity across an elevational gradient and a 140-year longecological experiment. We argue that our general TDT provides a baseline for(i) recasting the predictions of ecological theories based on species richnessin terms of the shape of trait distributions; and (ii) integrating how specifictraits, including body size, and functional diversity scale up to influence thedynamics of species assemblages across climatic gradients and how shifts infunctional composition influences ecosystem functioning. Further, it offers anovel framework to integrate trait, metabolic/allometric, and species-richnessbased approaches in order to build a more predictive functional biogeography toshow how assemblages of species have and will respond to climate change.[Journal_ref: 2015, Advances in Ecological Research, 52]
- Blonder, B., Nogues-Bravo, D., Borregaard, M. K., Donoghue, J., Jorgensen, P. M., Kraft, N., Lessard, J., Morueta-Holme, N., Sandel, B., Svenning, J., Violle, C., Rahbek, C., & Enquist, B. J. (2015). Linking environmental filtering and disequilibrium to biogeography with a community climate framework. ECOLOGY, 96(4), 972-985.
- Blonder, B., Nogués-Bravo, D., Borregaard, M. K., Donoghue, J. C., Jørgensen, P. M., Kraft, N. J., Lessard, J., Morueta-Holme, N., Sandel, B., Svenning, J., Violle, C., Rahbek, C., & Enquist, B. J. (2015). Linking environmental filtering and disequilibrium to biogeography with a community climate framework. Ecology, 96(4), 972-85.More infoWe present a framework to measure the strength of environmental filtering and disequilibrium of the species composition of a local community across time, relative to past, current, and future climates. We demonstrate the framework by measuring the impact of climate change on New World forests, integrating data for climate niches of more than 14000 species, community composition of 471 New World forest plots, and observed climate across the most recent glacial-interglacial interval. We show that a majority of communities have species compositions that are strongly filtered and are more in equilibrium with current climate than random samples from the regional pool. Variation in the level of current community disequilibrium can be predicted from Last Glacial Maximum climate and will increase with near-future climate change.
- Blonder, B., Vasseur, F., Violle, C., Shipley, B., Enquist, B. J., & Vile, D. (2015). Testing models for the leaf economics spectrum with leaf and whole-plant traits in Arabidopsis thaliana. AOB PLANTS, 7.
- Duncanson, L. I., Dubayah, R. O., & Enquist, B. J. (2015). Assessing the general patterns of forest structure: quantifying tree and forest allometric scaling relationships in the United States. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 24(12), 1465-1475.
- Engemann, K., Enquist, B. J., Sandel, B., Boyle, B., Jorgensen, P. M., Morueta-Holme, N., Peet, R. K., Violle, C., & Svenning, J. (2015). Limited sampling hampers "big data" estimation of species richness in a tropical biodiversity hotspot. ECOLOGY AND EVOLUTION, 5(3), 807-820.
- Engemann, K., Enquist, B. J., Sandel, B., Boyle, B., Jørgensen, P. M., Morueta-Holme, N., Peet, R. K., Violle, C., & Svenning, J. (2015). Limited sampling hampers "big data" estimation of species richness in a tropical biodiversity hotspot. Ecology and evolution, 5(3), 807-20.More infoMacro-scale species richness studies often use museum specimens as their main source of information. However, such datasets are often strongly biased due to variation in sampling effort in space and time. These biases may strongly affect diversity estimates and may, thereby, obstruct solid inference on the underlying diversity drivers, as well as mislead conservation prioritization. In recent years, this has resulted in an increased focus on developing methods to correct for sampling bias. In this study, we use sample-size-correcting methods to examine patterns of tropical plant diversity in Ecuador, one of the most species-rich and climatically heterogeneous biodiversity hotspots. Species richness estimates were calculated based on 205,735 georeferenced specimens of 15,788 species using the Margalef diversity index, the Chao estimator, the second-order Jackknife and Bootstrapping resampling methods, and Hill numbers and rarefaction. Species richness was heavily correlated with sampling effort, and only rarefaction was able to remove this effect, and we recommend this method for estimation of species richness with "big data" collections.
- Enquist, B. J., Norberg, J., Bonser, S. P., Violle, C., Webb, C. T., Henderson, A., Sloat, L. L., & Savage, V. M. (2015). Scaling from Traits to Ecosystems: Developing a General Trait Driver Theory via Integrating Trait-Based and Metabolic Scaling Theories. ADVANCES IN ECOLOGICAL RESEARCH, VOL 52: TRAIT-BASED ECOLOGY - FROM STRUCTURE TO FUNCTION, 52, 249-318.
- Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2015). Response to Comments on "Evidence for mesothermy in dinosaurs". SCIENCE, 348(6238).
- Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2015). Response to Comments on "Evidence for mesothermy in dinosaurs". Science (New York, N.Y.), 348(6238), 982.More infoD'Emic and Myhrvold raise a number of statistical and methodological issues with our recent analysis of dinosaur growth and energetics. However, their critiques and suggested improvements lack biological and statistical justification.
- Michaletz, S. T., Weiser, M. D., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2015). Plant Thermoregulation: Energetics, Trait-Environment Interactions, and Carbon Economics. TRENDS IN ECOLOGY & EVOLUTION, 30(12), 714-724.
- Michaletz, S. T., Weiser, M. D., Zhou, J., Kaspari, M., Helliker, B. R., & Enquist, B. J. (2015). Plant Thermoregulation: Energetics, Trait-Environment Interactions, and Carbon Economics. Trends in ecology & evolution, 30(12), 714-24.More infoBuilding a more predictive trait-based ecology requires mechanistic theory based on first principles. We present a general theoretical approach to link traits and climate. We use plant leaves to show how energy budgets (i) provide a foundation for understanding thermoregulation, (ii) explain mechanisms driving trait variation across environmental gradients, and (iii) guide selection on functional traits via carbon economics. Although plants are often considered to be poikilotherms, the data suggest that they are instead limited homeotherms. Leaf functional traits that promote limited homeothermy are adaptive because homeothermy maximizes instantaneous and lifetime carbon gain. This theory provides a process-based foundation for trait-climate analyses and shows that future studies should consider plant (not only air) temperatures.
- Simova, I., Violle, C., Kraft, N., Storch, D., Svenning, J., Boyle, B., Donoghue, J., Jorgensen, P., McGill, B. J., Morueta-Holme, N., Piel, W. H., Peet, R. K., Regetz, J., Schildhauer, M., Spencer, N., Thiers, B., Wiser, S., & Enquist, B. J. (2015). Shifts in trait means and variances in North American tree assemblages: species richness patterns are loosely related to the functional space. ECOGRAPHY, 38(7), 649-658.
- Sloat, L. L., Henderson, A. N., Lamanna, C., & Enquist, B. J. (2015). The Effect of the Foresummer Drought on Carbon Exchange in Subalpine Meadows. ECOSYSTEMS, 18(3), 533-545.
- Stark, S. C., Enquist, B. J., Saleska, S. R., Leitold, V., Schietti, J., Longo, M., Alves, L. F., Camargo, P. B., & Oliveira, R. C. (2015). Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography. ECOLOGY LETTERS, 18(7), 636-645.
- Stark, S. C., Enquist, B. J., Saleska, S. R., Leitold, V., Schietti, J., Longo, M., Alves, L. F., Camargo, P. B., & Oliveira, R. C. (2015). Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography. Ecology letters, 18(7), 636-45.More infoForest biophysical structure - the arrangement and frequency of leaves and stems - emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment-to-structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size-class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high-throughput approach to advance theory and investigate climate-relevant tropical forest change.
- Barnagaud, J., Daniel Kissling, W., Sandel, B., Eiserhardt, W. L., Sekercioğlu, C. H., Enquist, B. J., Tsirogiannis, C., & Svenning, J. (2014). Ecological traits influence the phylogenetic structure of bird species co-occurrences worldwide. Ecology letters, 17(7), 811-20.More infoThe extent to which species' ecological and phylogenetic relatedness shape their co-occurrence patterns at large spatial scales remains poorly understood. By quantifying phylogenetic assemblage structure within geographic ranges of >8000 bird species, we show that global co-occurrence patterns are linked - after accounting for regional effects - to key ecological traits reflecting diet, mobility, body size and climatic preference. We found that co-occurrences of carnivorous, migratory and cold-climate species are phylogenetically clustered, whereas nectarivores, herbivores, frugivores and invertebrate eaters tend to be more phylogenetically overdispersed. Preference for open or forested habitats appeared to be independent from the level of phylogenetic clustering. Our results advocate for an extension of the tropical niche conservatism hypothesis to incorporate ecological and life-history traits beyond the climatic niche. They further offer a novel species-oriented perspective on how biogeographic and evolutionary legacies interact with ecological traits to shape global patterns of species coexistence in birds.
- Barnagaud, J., Kissling, W. D., Sandel, B., Eiserhardt, W. L., Sekercioglu, C. H., Enquist, B. J., Tsirogiannis, C., & Svenning, J. (2014). Ecological traits influence the phylogenetic structure of bird species co-occurrences worldwide. ECOLOGY LETTERS, 17(7), 811-820.
- Blonder, B., & Enquist, B. J. (2014). Inferring climate from angiosperm leaf venation networks. NEW PHYTOLOGIST, 204(1), 116-126.
- Blonder, B., & Enquist, B. J. (2014). Inferring climate from angiosperm leaf venation networks. The New phytologist, 204(1), 116-26.More infoLeaf venation networks provide an integrative linkage between plant form, function and climate niche, because leaf water transport underlies variation in plant performance. Here, we develop theory based on leaf physiology that uses community-mean vein density to predict growing season temperature and atmospheric CO2 concentration. The key assumption is that leaf water supply is matched to water demand in the local environment. We test model predictions using leaves from 17 temperate and tropical sites that span broad climatic gradients. We find quantitative agreement between predicted and observed climate values. We also highlight additional leaf traits that may improve predictions. Our study provides a novel approach for understanding the functional linkages between functional traits and climate that may improve the reconstruction of paleoclimate from fossil assemblages.
- Blonder, B., Lamanna, C., Violle, C., & Enquist, B. J. (2014). The n-dimensional hypervolume. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 23(5), 595-609.
- Blonder, B., Lamanna, C., Violle, C., & Enquist, B. J. (2014). The n-dimensional hypervolume. Global Ecology and Biogeography, 23(5), 595-609.More infoAbstract: Aim: The Hutchinsonian hypervolume is the conceptual foundation for many lines of ecological and evolutionary inquiry, including functional morphology, comparative biology, community ecology and niche theory. However, extant methods to sample from hypervolumes or measure their geometry perform poorly on high-dimensional or holey datasets. Innovation: We first highlight the conceptual and computational issues that have prevented a more direct approach to measuring hypervolumes. Next, we present a new multivariate kernel density estimation method that resolves many of these problems in an arbitrary number of dimensions. Main conclusions: We show that our method (implemented as the 'hypervolume' R package) can match several extant methods for hypervolume geometry and species distribution modelling. Tools to quantify high-dimensional ecological hypervolumes will enable a wide range of fundamental descriptive, inferential and comparative questions to be addressed. © 2014 John Wiley & Sons Ltd.
- Blonder, B., Royer, D. L., Johnson, K. R., Miller, I., & Enquist, B. J. (2014). Plant Ecological Strategies Shift Across the Cretaceous-Paleogene Boundary. PLOS BIOLOGY, 12(9).
- Blonder, B., Royer, D. L., Johnson, K. R., Miller, I., & Enquist, B. J. (2014). Plant ecological strategies shift across the Cretaceous-Paleogene boundary. PLoS biology, 12(9), e1001949.More infoThe Chicxulub bolide impact caused the end-Cretaceous mass extinction of plants, but the associated selectivity and ecological effects are poorly known. Using a unique set of North Dakota leaf fossil assemblages spanning 2.2 Myr across the event, we show among angiosperms a reduction of ecological strategies and selection for fast-growth strategies consistent with a hypothesized recovery from an impact winter. Leaf mass per area (carbon investment) decreased in both mean and variance, while vein density (carbon assimilation rate) increased in mean, consistent with a shift towards "fast" growth strategies. Plant extinction from the bolide impact resulted in a shift in functional trait space that likely had broad consequences for ecosystem functioning.
- Blonder, B., Sloat, L., Enquist, B. J., & McGill, B. (2014). Separating macroecological pattern and process: comparing ecological, economic, and geological systems. PloS one, 9(11), e112850.More infoTheories of biodiversity rest on several macroecological patterns describing the relationship between species abundance and diversity. A central problem is that all theories make similar predictions for these patterns despite disparate assumptions. A troubling implication is that these patterns may not reflect anything unique about organizational principles of biology or the functioning of ecological systems. To test this, we analyze five datasets from ecological, economic, and geological systems that describe the distribution of objects across categories in the United States. At the level of functional form ('first-order effects'), these patterns are not unique to ecological systems, indicating they may reveal little about biological process. However, we show that mechanism can be better revealed in the scale-dependency of first-order patterns ('second-order effects'). These results provide a roadmap for biodiversity theory to move beyond traditional patterns, and also suggest ways in which macroecological theory can constrain the dynamics of economic systems.
- Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2014). Inclusion of vein traits improves predictive power for the leaf economic spectrum: a response to Sack et al. (2013). JOURNAL OF EXPERIMENTAL BOTANY, 65(18), 5109-5114.
- Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2014). Inclusion of vein traits improves predictive power for the leaf economic spectrum: a response to Sack et al. (2013). Journal of experimental botany, 65(18), 5109-14.More infoOur model for the worldwide leaf economics spectrum (LES) based on venation networks (Blonder et al., 2011, 2013) was strongly criticized by Sack et al. (2013) in this journal. Here, we show that the majority of criticisms by Sack et al. are based on mathematical and conceptual misunderstandings. Using empirical data from both our original study as well as others in the literature, we show support for our original hypothesis, that venation networks provide predictive power and conceptual unification for the LES. In an effort to reconcile differing viewpoints related to the role of leaf venation traits for the LES, we highlight several lines of further investigation.
- Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). DINOSAUR PHYSIOLOGY Evidence for mesothermy in dinosaurs. SCIENCE, 344(6189), 1268-1272.
- Grady, J. M., Enquist, B. J., Dettweiler-Robinson, E., Wright, N. A., & Smith, F. A. (2014). Dinosaur physiology. Evidence for mesothermy in dinosaurs. Science (New York, N.Y.), 344(6189), 1268-72.More infoWere dinosaurs ectotherms or fast-metabolizing endotherms whose activities were unconstrained by temperature? To date, some of the strongest evidence for endothermy comes from the rapid growth rates derived from the analysis of fossil bones. However, these studies are constrained by a lack of comparative data and an appropriate energetic framework. Here we compile data on ontogenetic growth for extant and fossil vertebrates, including all major dinosaur clades. Using a metabolic scaling approach, we find that growth and metabolic rates follow theoretical predictions across clades, although some groups deviate. Moreover, when the effects of size and temperature are considered, dinosaur metabolic rates were intermediate to those of endotherms and ectotherms and closest to those of extant mesotherms. Our results suggest that the modern dichotomy of endothermic versus ectothermic is overly simplistic.
- Lamanna, C., Blonder, B., Violle, C., Kraft, N. J., Sandel, B., Šímová, I., Donoghue, J. C., Svenning, J., McGill, B. J., Boyle, B., Buzzard, V., Dolins, S., Jørgensen, P. M., Marcuse-Kubitza, A., Morueta-Holme, N., Peet, R. K., Piel, W. H., Regetz, J., Schildhauer, M., , Spencer, N., et al. (2014). Functional trait space and the latitudinal diversity gradient. Proceedings of the National Academy of Sciences of the United States of America, 111(38), 13745-50.More infoThe processes causing the latitudinal gradient in species richness remain elusive. Ecological theories for the origin of biodiversity gradients, such as competitive exclusion, neutral dynamics, and environmental filtering, make predictions for how functional diversity should vary at the alpha (within local assemblages), beta (among assemblages), and gamma (regional pool) scales. We test these predictions by quantifying hypervolumes constructed from functional traits representing major axes of plant strategy variation (specific leaf area, plant height, and seed mass) in tree assemblages spanning the temperate and tropical New World. Alpha-scale trait volume decreases with absolute latitude and is often lower than sampling expectation, consistent with environmental filtering theory. Beta-scale overlap decays with geographic distance fastest in the temperate zone, again consistent with environmental filtering theory. In contrast, gamma-scale trait space shows a hump-shaped relationship with absolute latitude, consistent with no theory. Furthermore, the overall temperate trait hypervolume was larger than the overall tropical hypervolume, indicating that the temperate zone permits a wider range of trait combinations or that niche packing is stronger in the tropical zone. Although there are limitations in the data, our analyses suggest that multiple processes have shaped trait diversity in trees, reflecting no consistent support for any one theory.
- Lamanna, C., Blonder, B., Violle, C., Kraft, N., Sandel, B., Simova, I., Donoghue, J., Svenning, J., McGill, B. J., Boyle, B., Buzzard, V., Dolins, S., Jorgensen, P. M., Marcuse-Kubitza, A., Morueta-Holme, N., Peet, R. K., Piel, W. H., Regetz, J., Schildhauer, M., , Spencer, N., et al. (2014). Functional trait space and the latitudinal diversity gradient. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 111(38), 13745-13750.
- Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2014). Convergence of terrestrial plant production across global climate gradients. NATURE, 512(7512), 39-+.
- Michaletz, S. T., Cheng, D., Kerkhoff, A. J., & Enquist, B. J. (2014). Convergence of terrestrial plant production across global climate gradients. Nature, 512(7512), 39-43.More infoVariation in terrestrial net primary production (NPP) with climate is thought to originate from a direct influence of temperature and precipitation on plant metabolism. However, variation in NPP may also result from an indirect influence of climate by means of plant age, stand biomass, growing season length and local adaptation. To identify the relative importance of direct and indirect climate effects, we extend metabolic scaling theory to link hypothesized climate influences with NPP, and assess hypothesized relationships using a global compilation of ecosystem woody plant biomass and production data. Notably, age and biomass explained most of the variation in production whereas temperature and precipitation explained almost none, suggesting that climate indirectly (not directly) influences production. Furthermore, our theory shows that variation in NPP is characterized by a common scaling relationship, suggesting that global change models can incorporate the mechanisms governing this relationship to improve predictions of future ecosystem function.
- Sides, C. B., Enquist, B. J., Ebersole, J. J., Smith, M. N., Henderson, A. N., & Sloat, L. L. (2014). REVISITING DARWIN'S HYPOTHESIS: DOES GREATER INTRASPECIFIC VARIABILITY INCREASE SPECIES' ECOLOGICAL BREADTH?. AMERICAN JOURNAL OF BOTANY, 101(1), 56-62.
- Sides, C. B., Enquist, B. J., Ebersole, J. J., Smith, M. N., Henderson, A. N., & Sloat, L. L. (2014). Revisiting darwins hypothesis: Does greater intraspecific variability increase species ecological breadth?. American Journal of Botany, 101(1), 56-62.More infoAbstract: Premise of the study: Darwin first proposed that species with larger ecological breadth have greater phenotypic variation. We tested this hypothesis by comparing intraspecific variation in specific leaf area (SLA) to species' local elevational range and by assessing how external (abiotic) filters may influence observed differences in ecological breadth among species. Understanding the patterns of individual variation within and between populations will help evaluate differing hypotheses for structuring of communities and distribution of species. Methods: We selected 21 species with varying elevational ranges and compared the coefficient of variation of SLA for each species against its local elevational range. We examined the influence of external filters on local trait composition by determining if intraspecific changes in SLA with elevation have the same direction and similar rates of change as the change in community mean SLA value. Key results: In support of Darwin's hypothesis, we found a positive relationship between species' coefficient of variation for SLA with species' local elevational range. Intraspecific changes in SLA had the same sign, but generally lower magnitude than the community mean SLA. Conclusions: The results indicate that wide-ranging species are indeed characterized by greater intraspecific variation and that species' phenotypes shift along environmental gradients in the same direction as the community phenotypes. However, across species, the rate of intraspecific trait change, reflecting plastic and/or adaptive changes across populations, is limited and prevents species from adjusting to environmental gradients as quickly as interspecific changes resulting from community assembly. © 2014 Botanical Society of America.
- Smith, D. D., Sperry, J. S., Enquist, B. J., Savage, V. M., McCulloh, K. A., & Bentley, L. P. (2014). Deviation from symmetrically self-similar branching in trees predicts altered hydraulics, mechanics, light interception and metabolic scaling. NEW PHYTOLOGIST, 201(1), 217-229.
- Smith, D. D., Sperry, J. S., Enquist, B. J., Savage, V. M., McCulloh, K. A., & Bentley, L. P. (2014). Deviation from symmetrically self-similar branching in trees predicts altered hydraulics, mechanics, light interception and metabolic scaling. The New phytologist, 201(1), 217-29.More infoThe West, Brown, Enquist (WBE) model derives symmetrically self-similar branching to predict metabolic scaling from hydraulic conductance, K, (a metabolism proxy) and tree mass (or volume, V). The original prediction was Kα V(0.75). We ask whether trees differ from WBE symmetry and if it matters for plant function and scaling. We measure tree branching and model how architecture influences K, V, mechanical stability, light interception and metabolic scaling. We quantified branching architecture by measuring the path fraction, Pf : mean/maximum trunk-to-twig pathlength. WBE symmetry produces the maximum, Pf = 1.0. We explored tree morphospace using a probability-based numerical model constrained only by biomechanical principles. Real tree Pf ranged from 0.930 (nearly symmetric) to 0.357 (very asymmetric). At each modeled tree size, a reduction in Pf led to: increased K; decreased V; increased mechanical stability; and decreased light absorption. When Pf was ontogenetically constant, strong asymmetry only slightly steepened metabolic scaling. The Pf ontogeny of real trees, however, was 'U' shaped, resulting in size-dependent metabolic scaling that exceeded 0.75 in small trees before falling below 0.65. Architectural diversity appears to matter considerably for whole-tree hydraulics, mechanics, photosynthesis and potentially metabolic scaling. Optimal architectures likely exist that maximize carbon gain per structural investment.
- Smith, D. D., Sperry, J. S., Enquist, B. J., Savage, V. M., Mcculloh, K. A., & Bentley, L. P. (2014). Deviation from symmetrically self-similar branching in trees predicts altered hydraulics, mechanics, light interception and metabolic scaling. New Phytologist, 201(1), 217-229.More infoAbstract: Summary: The West, Brown, Enquist (WBE) model derives symmetrically self-similar branching to predict metabolic scaling from hydraulic conductance, K, (a metabolism proxy) and tree mass (or volume, V). The original prediction was K∝V0.75. We ask whether trees differ from WBE symmetry and if it matters for plant function and scaling. We measure tree branching and model how architecture influences K, V, mechanical stability, light interception and metabolic scaling. We quantified branching architecture by measuring the path fraction, Pf: mean/maximum trunk-to-twig pathlength. WBE symmetry produces the maximum, Pf = 1.0. We explored tree morphospace using a probability-based numerical model constrained only by biomechanical principles. Real tree Pf ranged from 0.930 (nearly symmetric) to 0.357 (very asymmetric). At each modeled tree size, a reduction in Pf led to: increased K; decreased V; increased mechanical stability; and decreased light absorption. When Pf was ontogenetically constant, strong asymmetry only slightly steepened metabolic scaling. The Pf ontogeny of real trees, however, was 'U' shaped, resulting in size-dependent metabolic scaling that exceeded 0.75 in small trees before falling below 0.65. Architectural diversity appears to matter considerably for whole-tree hydraulics, mechanics, photosynthesis and potentially metabolic scaling. Optimal architectures likely exist that maximize carbon gain per structural investment. © 2013 New Phytologist Trust.
- Violle, C., Reich, P. B., Pacala, S. W., Enquist, B. J., & Kattge, J. (2014). The emergence and promise of functional biogeography. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 111(38), 13690-13696.
- Violle, C., Reich, P. B., Pacala, S. W., Enquist, B. J., & Kattge, J. (2014). The emergence and promise of functional biogeography. Proceedings of the National Academy of Sciences of the United States of America, 111(38), 13690-6.More infoUnderstanding, modeling, and predicting the impact of global change on ecosystem functioning across biogeographical gradients can benefit from enhanced capacity to represent biota as a continuous distribution of traits. However, this is a challenge for the field of biogeography historically grounded on the species concept. Here we focus on the newly emergent field of functional biogeography: the study of the geographic distribution of trait diversity across organizational levels. We show how functional biogeography bridges species-based biogeography and earth science to provide ideas and tools to help explain gradients in multifaceted diversity (including species, functional, and phylogenetic diversities), predict ecosystem functioning and services worldwide, and infuse regional and global conservation programs with a functional basis. Although much recent progress has been made possible because of the rising of multiple data streams, new developments in ecoinformatics, and new methodological advances, future directions should provide a theoretical and comprehensive framework for the scaling of biotic interactions across trophic levels and its ecological implications.
- Bentley, L. P., Stegen, J. C., Savage, V. M., Smith, D. D., I., E., Sperry, J. S., Reich, P. B., & Enquist, B. J. (2013). An empirical assessment of tree branching networks and implications for plant allometric scaling models. Ecology Letters, 16(8), 1069-1078.More infoPMID: 23800188;Abstract: Several theories predict whole-tree function on the basis of allometric scaling relationships assumed to emerge from traits of branching networks. To test this key assumption, and more generally, to explore patterns of external architecture within and across trees, we measure branch traits (radii/lengths) and calculate scaling exponents from five functionally divergent species. Consistent with leading theories, including metabolic scaling theory, branching is area preserving and statistically self-similar within trees. However, differences among scaling exponents calculated at node- and whole-tree levels challenge the assumption of an optimised, symmetrically branching tree. Furthermore, scaling exponents estimated for branch length change across branching orders, and exponents for scaling metabolic rate with plant size (or number of terminal tips) significantly differ from theoretical predictions. These findings, along with variability in the scaling of branch radii being less than for branch lengths, suggest extending current scaling theories to include asymmetrical branching and differential selective pressures in plant architectures. © 2013 John Wiley & Sons Ltd/CNRS.
- Bentley, L. P., Stegen, J. C., Savage, V. M., Smith, D. D., von, A., Sperry, J. S., Reich, P. B., & Enquist, B. J. (2013). An empirical assessment of tree branching networks and implications for plant allometric scaling models. ECOLOGY LETTERS, 16(8), 1069-1078.
- Blonder, B., Violle, C., & Enquist, B. J. (2013). Assessing the causes and scales of the leaf economics spectrum using venation networks in Populus tremuloides. JOURNAL OF ECOLOGY, 101(4), 981-989.
- Blonder, B., Violle, C., & Enquist, B. J. (2013). Assessing the causes and scales of the leaf economics spectrum using venation networks in Populus tremuloides. Journal of Ecology, 101(4), 981-989.More infoAbstract: The leaf economics spectrum (LES) describes global interspecific correlations between leaf traits. Despite recent theoretical advances, the biological scale at which LES correlations emerge and the physiological and climatic causes of these correlations remains partially unknown. Here, we test an extant theory based on universal trade-offs in leaf venation networks that predicts that (i) the LES primarily originates within individuals; (ii) minor vein density drives LES trait correlations; and (iii) between individuals, LES correlations reflects variation in minor vein density driven by water availability. To test these predictions, we sample leaves within and between clones of Populus tremuloides across a wide climate gradient. We show that predictions i) and iii) are supported but ii) is only partially supported. To account for this discrepancy, we develop a more general venation theory. This theory describes linkages between vein density, leaf area and leaf thickness that can modulate LES correlations across scales. This theory helps to identify multiple selective pressures that can drive trait covariation underlying the LES. Synthesis. Our results broaden the range of biological scales at which the leaf economics spectrum (LES) is found and highlight the complex causal roles of venation networks in LES correlations. This study points to the need to better understand the coupling between venation networks, leaf size and climate to fully understand the LES. © 2013 The Authors. Journal of Ecology © 2013 British Ecological Society.
- Boyle, B., Hopkins, N., Lu, Z., Garay, J., Mozzherin, D., Rees, T., Matasci, N., Narro, M. L., Piel, W. H., Mckay, S. J., Lowry, S., Freeland, C., Peet, R. K., & Enquist, B. J. (2013). The taxonomic name resolution service: an online tool for automated standardization of plant names. BMC BIOINFORMATICS, 14.
- Charney, N., Babst, F., Poulter, B., Record, S., Trouet, V. M., Frank, D., Enquist, B. J., & Evans, M. E. (2015). Observed forest sensitivity to climate implies larger reductions in 21st century forest growth. Ecology Letters.
- Enquist, B., Boyle, B., Hopkins, N., Lu, Z., Raygoza Garay, J. A., Mozzherin, D., Rees, T., Matasci, N., Narro, M. L., Piel, W. H., McKay, S. J., Lowry, S., Freeland, C., Peet, R. K., & Enquist, B. J. (2013). The taxonomic name resolution service: an online tool for automated standardization of plant names. BMC bioinformatics, 14.More infoThe digitization of biodiversity data is leading to the widespread application of taxon names that are superfluous, ambiguous or incorrect, resulting in mismatched records and inflated species numbers. The ultimate consequences of misspelled names and bad taxonomy are erroneous scientific conclusions and faulty policy decisions. The lack of tools for correcting this 'names problem' has become a fundamental obstacle to integrating disparate data sources and advancing the progress of biodiversity science.
- Hulshof, C. M., Violle, C., Spasojevic, M. J., McGill, B., Damschen, E., Harrison, S., & Enquist, B. J. (2013). Intra-specific and inter-specific variation in specific leaf area reveal the importance of abiotic and biotic drivers of species diversity across elevation and latitude. JOURNAL OF VEGETATION SCIENCE, 24(5), 921-931.
- Hulshof, C. M., Violle, C., Spasojevic, M. J., Mcgill, B., Damschen, E., Harrison, S., & Enquist, B. J. (2013). Intra-specific and inter-specific variation in specific leaf area reveal the importance of abiotic and biotic drivers of species diversity across elevation and latitude. Journal of Vegetation Science, 24(5), 921-931.More infoAbstract: Questions: Are patterns of intra- and inter-specific functional trait variation consistent with greater abiotic filtering on community assembly at high latitudes and elevations, and greater biotic filtering at low latitudes and elevations? Locations: Area de Conservación Guanacaste, Costa Rica; Santa Catalina Mountains, Arizona; Siskiyou Mountains, Oregon. Methods: We measured woody plant species abundance and a key functional trait associated with competition for resources and environmental tolerance (specific leaf area, SLA) along elevational gradients in low-latitude tropical (Costa Rica), mid-latitude desert (Arizona) and high latitude mediterranean (southern Oregon) biomes. We explored patterns of abiotic and biotic filtering by comparing observed patterns of community-weighted means and variances along elevational and latitudinal gradients to those expected under random assembly. In addition, we related trait variability to niches and explored how total trait space and breadth vary across broad spatial gradients by quantifying the ratio of intra- to inter-specific variation. Results: Both the community-wide mean and variance of SLA decreased with increasing latitude, consistent with greater abiotic filtering at higher latitudes. Further, low-elevation communities had higher trait variation than expected by chance, consistent with greater biotic filtering at low elevations. Finally, in the tropics and across latitude the ratio of intra- to inter-specific variation was negatively correlated to species richness, which further suggests that biotic interactions influence plant assembly at low latitudes. Conclusions: Intra- and inter-specific patterns of SLA variation appeared broadly consistent with the idea that the relative strength of biotic and abiotic drivers on community assembly changes along elevational and latitudinal gradients; evidence for biotic drivers appeared more prominent at low latitudes and elevations and evidence for abiotic drivers appeared more prominent at high latitudes and elevations. © 2013 International Association for Vegetation Science.
- Moles, A. T., Peco, B., Wallis, I. R., Foley, W. J., G., A., Seabloom, E. W., Vesk, P. A., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnæs, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magaña-Rodríguez, B., , Moore, B. D., et al. (2013). Correlations between physical and chemical defences in plants: Tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?. New Phytologist, 198(1), 252-263.More infoPMID: 23316750;Abstract: Most plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.
- Moles, A. T., Peco, B., Wallis, I. R., Foley, W. J., Poore, A. G., Seabloom, E. W., Vesk, P. A., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnaes, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magaña-Rodríguez, B., , Moore, B. D., et al. (2013). Correlations between physical and chemical defences in plants: tradeoffs, syndromes, or just many different ways to skin a herbivorous cat?. The New phytologist, 198(1), 252-263.More infoMost plant species have a range of traits that deter herbivores. However, understanding of how different defences are related to one another is surprisingly weak. Many authors argue that defence traits trade off against one another, while others argue that they form coordinated defence syndromes. We collected a dataset of unprecedented taxonomic and geographic scope (261 species spanning 80 families, from 75 sites across the globe) to investigate relationships among four chemical and six physical defences. Five of the 45 pairwise correlations between defence traits were significant and three of these were tradeoffs. The relationship between species' overall chemical and physical defence levels was marginally nonsignificant (P = 0.08), and remained nonsignificant after accounting for phylogeny, growth form and abundance. Neither categorical principal component analysis (PCA) nor hierarchical cluster analysis supported the idea that species displayed defence syndromes. Our results do not support arguments for tradeoffs or for coordinated defence syndromes. Rather, plants display a range of combinations of defence traits. We suggest this lack of consistent defence syndromes may be adaptive, resulting from selective pressure to deploy a different combination of defences to coexisting species.
- Morueta-Holme, N., Enquist, B. J., McGill, B. J., Boyle, B., Jorgensen, P. M., Ott, J. E., Peet, R. K., Simova, I., Sloat, L. L., Thiers, B., Violle, C., Wiser, S. K., Dolins, S., Donoghue, J., Kraft, N., Regetz, J., Schildhauer, M., Spencer, N., & Svenning, J. (2013). Habitat area and climate stability determine geographical variation in plant species range sizes. ECOLOGY LETTERS, 16(12), 1446-1454.
- Morueta-Holme, N., Enquist, B. J., Mcgill, B. J., Boyle, B., Jørgensen, P. M., Ott, J. E., Peet, R. K., Šímová, I., Sloat, L. L., Thiers, B., Violle, C., Wiser, S. K., Dolins, S., Donoghue, J. C., Kraft, N. J., Regetz, J., Schildhauer, M., Spencer, N., & Svenning, J. (2013). Habitat area and climate stability determine geographical variation in plant species range sizes. Ecology Letters, 16(12), 1446-1454.More infoAbstract: Despite being a fundamental aspect of biodiversity, little is known about what controls species range sizes. This is especially the case for hyperdiverse organisms such as plants. We use the largest botanical data set assembled to date to quantify geographical variation in range size for ~ 85 000 plant species across the New World. We assess prominent hypothesised range-size controls, finding that plant range sizes are codetermined by habitat area and long- and short-term climate stability. Strong short- and long-term climate instability in large parts of North America, including past glaciations, are associated with broad-ranged species. In contrast, small habitat areas and a stable climate characterise areas with high concentrations of small-ranged species in the Andes, Central America and the Brazilian Atlantic Rainforest region. The joint roles of area and climate stability strengthen concerns over the potential effects of future climate change and habitat loss on biodiversity. © 2013 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.
- Stegen, J. C., Ferriere, R., & Enquist, B. J. (2013). Evolving ecological networks and the emergence of biodiversity patterns across temperature gradients. PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES, 279(1731), 1051-1060.
- Stegen, J. C., Swenson, N. G., Valencia, R., Enquist, B. J., & Thompson, J. (2013). Above-ground forest biomass is not consistently related to wood density in tropical forests. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 18(5), 617-625.
- Blonder, B., Buzzard, V., Simova, I., Sloat, L., Boyle, B., Lipson, R., Aguilar-Beaucage, B., Andrade, A., Barber, B., Barnes, C., Bushey, D., Cartagena, P., Chaney, M., Contreras, K., Cox, M., Cueto, M., Curtis, C., Fisher, M., Furst, L., , Gallegos, J., et al. (2012). THE LEAF-AREA SHRINKAGE EFFECT CAN BIAS PALEOCLIMATE AND ECOLOGY RESEARCH. AMERICAN JOURNAL OF BOTANY, 99(11), 1756-1763.
- Blonder, B., De, C. F., Moore, J., Rivers, M., & Enquist, B. J. (2012). X-ray imaging of leaf venation networks. NEW PHYTOLOGIST, 196(4), 1274-1282.
- Enquist, B. J., & Bentley, L. P. (2012). Land Plants: New Theoretical Directions and Empirical Prospects. Metabolic Ecology: A Scaling Approach, 164-187.
- Enquist, B., Blonder, B., Buzzard, V., Simova, I., Sloat, L., Boyle, B., Lipson, R., Aguilar-Beaucage, B., Andrade, A., Barber, B., Barnes, C., Bushey, D., Cartagena, P., Chaney, M., Contreras, K., Cox, M., Cueto, M., Curtis, C., Fisher, M., , Furst, L., et al. (2012). The leaf-area shrinkage effect can bias paleoclimate and ecology research. American journal of botany, 99(11).More infoLeaf area is a key trait that links plant form, function, and environment. Measures of leaf area can be biased because leaf area is often estimated from dried or fossilized specimens that have shrunk by an unknown amount. We tested the common assumption that this shrinkage is negligible.
- Enquist, B., Blonder, B., De Carlo, F., Moore, J., Rivers, M., & Enquist, B. J. (2012). X-ray imaging of leaf venation networks. The New phytologist, 196(4).More infoLeaf venation networks mediate many plant resource fluxes and are therefore of broad interest to research questions in plant physiology, systematics, paleoecology, and physics. However, the study of these networks is limited by slow and destructive imaging methods. X-ray imaging of leaf veins is potentially rapid, of high resolution, and nondestructive. Here, we have developed theory for absorption- and phase-contrast X-ray imaging. We then experimentally test these approaches using a synchrotron light source and two commercially available X-ray instruments. Using synchrotron light, we found that major veins could be consistently visualized using absorption-contrast imaging with X-ray energies
- Enquist, B., Hulshof, C. M., Stegen, J. C., Swenson, N. G., Enquist, C. A., & Enquist, B. J. (2012). Interannual variability of growth and reproduction in Bursera simaruba: the role of allometry and resource variability. Ecology, 93(1).More infoPlants are expected to differentially allocate resources to reproduction, growth, and survival in order to maximize overall fitness. Life history theory predicts that the allocation of resources to reproduction should occur at the expense of vegetative growth. Although it is known that both organism size and resource availability can influence life history traits, few studies have addressed how size dependencies of growth and reproduction and variation in resource supply jointly affect the coupling between growth and reproduction. In order to understand the relationship between growth and reproduction in the context of resource variability, we utilize a long-term observational data set consisting of 670 individual trees over a 10-year period within a local population of Bursera simaruba (L.) Sarg. We (1) quantify the functional form and variability in the growth-reproduction relationship at the population and individual-tree level and (2) develop a theoretical framework to understand the allometric dependence of growth and reproduction. Our findings suggest that the differential responses of allometric growth and reproduction to resource availability, both between years and between microsites, underlie the apparent relationship between growth and reproduction. Finally, we offer an alternative approach for quantifying the relationship between growth and reproduction that accounts for variation in allometries.
- Fuller, M. M., & Enquist, B. J. (2012). Accounting for spatial autocorrelation in null models of tree species association. ECOGRAPHY, 35(6), 510-518.
- Fuller, M. M., & Enquist, B. J. (2012). Accounting for spatial autocorrelation in null models of tree species association. Ecography, 35(6), 510-518.More infoAbstract: A commonly used null model for species association among forest trees is a well-mixed community (WMC). A WMC represents a non-spatial, or spatially implicit, model, in which species form nearest-neighbor pairs at a rate equal to the product of their community proportions. WMC models assume that the outcome of random dispersal and demographic processes is complete spatial randomness (CSR) in the species' spatial distributions. Yet, stochastic dispersal processes often lead to spatial autocorrelation (SAC) in tree species densities, giving rise to clustering, segregation, and other nonrandom patterns. Although methods exist to account for SAC in spatially-explicit models, its impact on non-spatial models often remains unaccounted for. To investigate the potential for SAC to bias tests based upon non-spatial models, we developed a spatially-heterogeneous (SH) modelling approach that incorporates measured levels of SAC. Using the mapped locations of individuals in a tropical tree community, we tested the hypothesis that the identity of nearest-neighbors represents a random draw from neighborhood species pools. Correlograms of Moran's I confirmed that, for 50 of 51 dominant species, stem density was significantly autocorrelated over distances ranging from 50 to 200 m. The observed patterns of SAC were consistent with dispersal limitation, with most species occurring in distinct patches. For nearly all of the 106 species in the community, the frequency of pairwise association was statistically indistinguishable from that projected by the null models. However, model comparisons revealed that non-spatial models more strongly underestimated observed species-pair frequencies, particularly for conspecific pairs. Overall, the CSR models projected more significant facilitative interactions than did SH models, yielding a more liberal test of niche differences. Our results underscore the importance of accounting for stochastic spatial processes in tests of association, regardless of whether spatial or non-spatial models are employed. © 2011 The Authors. Ecography © 2011 Nordic Society Oikos.
- Hulshof, C. M., Stegen, J. C., Swenson, N. G., Enquist, C., & Enquist, B. J. (2012). Interannual variability of growth and reproduction in Bursera simaruba: the role of allometry and resource variability. ECOLOGY, 93(1), 180-190.
- I., E., Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., Reich, P. B., & Bentley, L. P. (2012). A species-level model for metabolic scaling of trees II. Testing in a ring- and diffuse-porous species. Functional Ecology, 26(5), 1066-1076.More infoAbstract: A 17-parameter 'species model' that predicts metabolic scaling from vascular architecture was tested in a diffuse-porous maple (Acer grandidentatum) and a ring-porous oak (Quercus gambelii). Predictions of midday water transport (Q) and its scaling with above-ground mass (M) were compared with empirical measurements. We also tested the assumption that Q was proportional to the biomass growth rate of the shoot (G). Water transport and biomass growth rate were measured on 18 trees per species that spanned a broad range in trunk diameter (4-26 cm). Where possible, the same trees were used for obtaining the 17 model parameters that concern external branching, internal xylem conduit anatomy, and soil-to-canopy sap pressure drop. The model succeeded in predicting the Q by M b scaling exponent, b, being within 8% (maple) and 6% (oak) of measured exponents from sap flow data. In terms of absolute Q, the model was better in maple (16% Q overestimate) than oak (128% overestimate). The overestimation of Q was consistent with the model not accounting for cavitation, which is reportedly more prevalent in oak than in maple at the study site. The modelled and measured Q by M b exponents averaged within 3·6% of the measured G by M b exponents, supporting the assumption that G ∝ Q 1. The average b exponent was 0·62 ± 0·016 (mean ± SE) across species, rejecting b = 0·75 for intraspecific scaling. The performance of this species model, both for scaling purposes as well as for predicting rates of water consumption within and between species, argues for its further refinement and wider application in ecology and ecosystem biology. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
- Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., McCulloh, K. A., Reich, P. B., Bentley, L. P., & I., E. (2012). A species-level model for metabolic scaling in trees I. Exploring boundaries to scaling space within and across species. Functional Ecology, 26(5), 1054-1065.More infoAbstract: Metabolic scaling theory predicts how tree water flow rate (Q) scales with tree mass (M) and assumes identical scaling for biomass growth rate (G) with M. Analytic models have derived general scaling expectations from proposed optima in the rate of axial xylem conduit taper (taper function) and the allocation of wood space to water conduction (packing function). Recent predictions suggest G and Q scale with M to the ≈ 0·7 power with 0·75 as an upper bound. We complement this a priori optimization approach with a numerical model that incorporates species-specific taper and packing functions, plus additional empirical inputs essential for predicting Q (effects of gravity, tree size, heartwood, bark, and hydraulic resistance of leaf, root and interconduit pits). Traits are analysed individually, and in ensemble across tree types, to define a 2D 'scaling space' of absolute Q vs. its scaling exponent with tree size. ll traits influenced Q and many affected its scaling with M. Constraints driving the optimization of taper or packing functions, or any other trait, can be relaxed via compensatory changes in other traits. The scaling space of temperate trees overlapped despite diverse anatomy and winter-adaptive strategies. More conducting space in conifer wood compensated for narrow tracheids; extensive sapwood in diffuse-porous trees compensated for narrow vessels; and limited sapwood in ring-porous trees negated the effect of large vessels. Tropical trees, however, achieved the greatest Q and steepest size-scaling by pairing large vessels with extensive sapwood, a combination compatible with minimal water stress and no freezing-stress. Intraspecific scaling across all types averaged Q ∝ M 0·63 (maximum = Q ∝ M 0·71) for size-invariant root-shoot ratio. Scaling reached Q ∝ M 0·75 only if conductance increased faster in roots than in shoots with size. Interspecific scaling could reach Q ∝ M 0·75, but this may require the evolution of size-biased allometries rather than arising directly from biophysical constraints. Our species-level model is more realistic than its analytical predecessors and provides a tool for interpreting the adaptive significance of functional trait diversification in relation to whole-tree water use and consequent metabolic scaling. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
- Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., McCulloh, K. A., Reich, P. B., Bentley, L. P., & von, A. (2012). A species-level model for metabolic scaling in trees I. Exploring boundaries to scaling space within and across species. FUNCTIONAL ECOLOGY, 26(5), 1054-1065.
- Stegen, J. C., Enquist, B. J., & Ferriere, R. (2012). Advancing the metabolic theory of biodiversity. ECOLOGY LETTERS, 12(10), 1001-1015.
- Stegen, J. C., Enquist, B. J., & Ferriere, R. (2012). Eco-Evolutionary Community Dynamics: Covariation between Diversity and Invasibility across Temperature Gradients. AMERICAN NATURALIST, 180(4), E110-E126.
- Stegen, J. C., Enquist, B. J., & Ferrière, R. (2012). Eco-evolutionary community dynamics: covariation between diversity and invasibility across temperature gradients. The American naturalist, 180(4), E110-26.More infoUnderstanding biodiversity gradients is a long-standing challenge, and progress requires theory unifying ecology and evolution. Here, we unify concepts related to the speed of evolution, the influence of species richness on diversification, and niche-based coexistence. We focus on the dynamics, through evolutionary time, of community invasibility and species richness across a broad thermal gradient. In our framework, the evolution of body size influences the ecological structure and dynamics of a trophic network, and organismal metabolism ties temperature to eco-evolutionary processes. The framework distinguishes ecological invasibility (governed by ecological interactions) from evolutionary invasibility (governed by local ecology and constraints imposed by small phenotypic effects of mutation). The model yields four primary predictions: (1) ecological invasibility declines through time and with increasing temperature; (2) average evolutionary invasibility across communities increases and then decreases through time as the richness-temperature gradient flattens; (3) in the early stages of diversification, richness and evolutionary invasibility both increase with increasing temperature; and (4) at equilibrium, richness does not vary with temperature, yet evolutionary invasibility decreases with increasing temperature. These predictions emerge from the "evolutionary-speed" hypothesis, which attempts to account for latitudinal species richness gradients by invoking faster biological rates in warmer, tropical regions. The model contrasts with predictions from other richness-gradient hypotheses, such as "niche conservatism" and "species energy." Empirically testing our model's predictions should help distinguish among these hypotheses.
- Stegen, J. C., Ferriere, R., & Enquist, B. J. (2012). Evolving ecological networks and the emergence of biodiversity patterns across temperature gradients. Proceedings. Biological sciences, 279(1731), 1051-60.More infoIn ectothermic organisms, it is hypothesized that metabolic rates mediate influences of temperature on the ecological and evolutionary processes governing biodiversity. However, it is unclear how and to what extent the influence of temperature on metabolism scales up to shape large-scale diversity patterns. In order to clarify the roles of temperature and metabolism, new theory is needed. Here, we establish such theory and model eco-evolutionary dynamics of trophic networks along a broad temperature gradient. In the model temperature can influence, via metabolism, resource supply, consumers' vital rates and mutation rate. Mutation causes heritable variation in consumer body size, which diversifies and governs consumer function in the ecological network. The model predicts diversity to increase with temperature if resource supply is temperature-dependent, whereas temperature-dependent consumer vital rates cause diversity to decrease with increasing temperature. When combining both thermal dependencies, a unimodal temperature-diversity pattern evolves, which is reinforced by temperature-dependent mutation rate. Studying coexistence criteria for two consumers showed that these outcomes are owing to temperature effects on mutual invasibility and facilitation. Our theory shows how and why metabolism can influence diversity, generates predictions useful for understanding biodiversity gradients and represents an extendable framework that could include factors such as colonization history and niche conservatism.
- Swenson, N. G., Enquist, B. J., Pither, J., Kerkhoff, A. J., Boyle, B., Weiser, M. D., Elser, J. J., Fagan, W. F., Forero-Montana, J., Fyllas, N., Kraft, N., Lake, J. K., Moles, A. T., Patino, S., Phillips, O. L., Price, C. A., Reich, P. B., Quesada, C. A., Stegen, J. C., , Valencia, R., et al. (2012). The biogeography and filtering of woody plant functional diversity in North and South America. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 21(8), 798-808.
- Swenson, N. G., Enquist, B. J., Pither, J., Kerkhoff, A. J., Boyle, B., Weiser, M. D., Elser, J. J., Fagan, W. F., Forero-Montaña, J., Fyllas, N., J., N., Lake, J. K., Moles, A. T., Patiño, S., Phillips, O. L., Price, C. A., Reich, P. B., Quesada, C. A., Stegen, J. C., , Valencia, R., et al. (2012). The biogeography and filtering of woody plant functional diversity in North and South America. Global Ecology and Biogeography, 21(8), 798-808.More infoAbstract: Aim In recent years evidence has accumulated that plant species are differentially sorted from regional assemblages into local assemblages along local-scale environmental gradients on the basis of their function and abiotic filtering. The favourability hypothesis in biogeography proposes that in climatically difficult regions abiotic filtering should produce a regional assemblage that is less functionally diverse than that expected given the species richness and the global pool of traits. Thus it seems likely that differential filtering of plant traits along local-scale gradients may scale up to explain the distribution, diversity and filtering of plant traits in regional-scale assemblages across continents. The present work aims to address this prediction. Location North and South America. Methods We combine a dataset comprising over 5.5 million georeferenced plant occurrence records with several large plant functional trait databases in order to: (1) quantify how several critical traits associated with plant performance and ecology vary across environmental gradients; and (2) provide the first test of whether the woody plants found within 1° and 5° map grid cells are more or less functionally diverse than expected, given their species richness, across broad gradients. Results The results show that, for many of the traits studied, the overall distribution of functional traits in tropical regions often exceeds the expectations of random sampling given the species richness. Conversely, temperate regions often had narrower functional trait distributions than their smaller species pools would suggest. Main conclusion The results show that the overall distribution of function does increase towards the equator, but the functional diversity within regional-scale tropical assemblages is higher than that expected given their species richness. These results are consistent with the hypothesis that abiotic filtering constrains the overall distribution of function in temperate assemblages, but tropical assemblages are not as tightly constrained. © 2011 Blackwell Publishing Ltd.
- Vasseur, F., Violle, C., Enquist, B. J., Granier, C., & Vile, D. (2012). A common genetic basis to the origin of the leaf economics spectrum and metabolic scaling allometry. ECOLOGY LETTERS, 15(10), 1149-1157.
- Vasseur, F., Violle, C., Enquist, B. J., Granier, C., & Vile, D. (2012). A common genetic basis to the origin of the leaf economics spectrum and metabolic scaling allometry. Ecology Letters, 15(10), 1149-1157.More infoPMID: 22856883;Abstract: Many facets of plant form and function are reflected in general cross-taxa scaling relationships. Metabolic scaling theory (MST) and the leaf economics spectrum (LES) have each proposed unifying frameworks and organisational principles to understand the origin of botanical diversity. Here, we test the evolutionary assumptions of MST and the LES using a cross of two genetic variants of Arabidopsis thaliana. We show that there is enough genetic variation to generate a large fraction of variation in the LES and MST scaling functions. The progeny sharing the parental, naturally occurring, allelic combinations at two pleiotropic genes exhibited the theorised optimum 3/4 allometric scaling of growth rate and intermediate leaf economics. Our findings: (1) imply that a few pleiotropic genes underlie many plant functional traits and life histories; (2) unify MST and LES within a common genetic framework and (3) suggest that observed intermediate size and longevity in natural populations originate from stabilising selection to optimise physiological trade-offs. © 2012 Blackwell Publishing Ltd/CNRS.
- Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2012). The return of the variance: Intraspecific variability in community ecology. Trends in Ecology and Evolution, 27(4), 244-252.More infoPMID: 22244797;Abstract: Despite being recognized as a promoter of diversity and a condition for local coexistence decades ago, the importance of intraspecific variance has been neglected over time in community ecology. Recently, there has been a new emphasis on intraspecific variability. Indeed, recent developments in trait-based community ecology have underlined the need to integrate variation at both the intraspecific as well as interspecific level. We introduce new T-statistics ('T' for trait), based on the comparison of intraspecific and interspecific variances of functional traits across organizational levels, to operationally incorporate intraspecific variability into community ecology theory. We show that a focus on the distribution of traits at local and regional scales combined with original analytical tools can provide unique insights into the primary forces structuring communities. © 2011 Elsevier Ltd.
- Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2012). Viva la variance! A reply to Nakagawa & Schielzeth. Trends in Ecology and Evolution, 27(9), 475-476.
- von, A., Sperry, J. S., Smith, D. D., Savage, V. M., Enquist, B. J., Reich, P. B., & Bentley, L. P. (2012). A species-level model for metabolic scaling of trees II. Testing in a ring- and diffuse-porous species. FUNCTIONAL ECOLOGY, 26(5), 1066-1076.
- Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2011). Venation networks and the origin of the leaf economics spectrum. ECOLOGY LETTERS, 14(2), 91-100.
- Enquist, B. J., & A., C. (2011). Long-term change within a Neotropical forest: Assessing differential functional and floristic responses to disturbance and drought. Global Change Biology, 17(3), 1408-1424.More infoAbstract: Disentangling the relative roles of biotic and abiotic forces influencing forest structure, function, and local community composition continues to be an important goal in ecology. Here, utilizing two forest surveys 20-year apart from a Central American dry tropical forest, we assess the relative role of past disturbance and local climatic change in the form of increased drought in driving forest dynamics. We observe: (i) a net decrease in the number of trees; (ii) a decrease in total forest biomass by 7.7Mgha-1 but when calculated on subquadrat basis the biomass per unit area did not change indicating scale sensitivity of forest biomass measures; (iii) that the decrease in the number of stems occurred mainly in the smallest sizes, and in more moist and evergreen habitats; (iv) that there has been an increase in the proportion of trees that are deciduous, compound leaved and are canopy species, and a concomitant reduction in trees that are evergreen, simple-leaved, and understory species. These changes are opposite to predictions based on recovery from disturbance, and have resulted in (v) a uniform multivariate shift from a more mesic to a more xeric forest. Together, our results show that over relatively short time scales, community composition and the functional dominance may be more responsive to climate change than recovery to past disturbances. Our findings point to the importance of assessing proportional changes in forest composition and not just changes in absolute numbers. Our findings are also consistent with the hypothesis that tropical tree species exhibit differential sensitivity to changes in precipitation. Predicted future decreases in rainfall may result in quick differential shifts in forest function, physiognomy, and species composition. Quantifying proportional functional composition offers a basis for a predictive framework for how the structure, and diversity of tropical forests will respond to global change. © 2010 Blackwell Publishing Ltd.
- Enquist, B. J., & Enquist, C. (2011). Long-term change within a Neotropical forest: assessing differential functional and floristic responses to disturbance and drought. GLOBAL CHANGE BIOLOGY, 17(3), 1408-1424.
- Enquist, B., & Enquist, B. J. (2011). Forest annual carbon cost: comment. Ecology, 92(10).
- Enquist, B., Blonder, B., Violle, C., Bentley, L. P., & Enquist, B. J. (2011). Venation networks and the origin of the leaf economics spectrum. Ecology letters, 14(2).More infoThe leaf economics spectrum describes biome-invariant scaling functions for leaf functional traits that relate to global primary productivity and nutrient cycling. Here, we develop a comprehensive framework for the origin of this leaf economics spectrum based on venation-mediated economic strategies. We define a standardized set of traits - density, distance and loopiness - that provides a common language for the study of venation. We develop a novel quantitative model that uses these venation traits to model leaf-level physiology, and show that selection to optimize the venation network predicts the mean global trait-trait scaling relationships across 2548 species. Furthermore, using empirical venation data for 25 plant species, we test our model by predicting four key leaf functional traits related to leaf economics: net carbon assimilation rate, life span, leaf mass per area ratio and nitrogen content. Together, these results indicate that selection on venation geometry is a fundamental basis for understanding the diversity of leaf form and function, and the carbon balance of leaves. The model and associated predictions have broad implications for integrating venation network geometry with pattern and process in ecophysiology, ecology and palaeobotany.
- Fuller, M. M., Wagner, A., & Enquist, B. J. (2011). Using network analysis to characterize forest structure. NATURAL RESOURCE MODELING, 21(2), 225-247.
- Goff, S. A., Vaughn, M., McKay, S., Lyons, E., Stapleton, A. E., Gessler, D., Matasci, N., Wang, L., Hanlon, M., Lenards, A., Muir, A., Merchant, N., Lowry, S., Mock, S., Helmke, M., Kubach, A., Narro, M., Hopkins, N., Micklos, D., , Hilgert, U., et al. (2011). The iPlant Collaborative: Cyberinfrastructure for Plant Biology. Frontiers in plant science, 2, 34.More infoThe iPlant Collaborative (iPlant) is a United States National Science Foundation (NSF) funded project that aims to create an innovative, comprehensive, and foundational cyberinfrastructure in support of plant biology research (PSCIC, 2006). iPlant is developing cyberinfrastructure that uniquely enables scientists throughout the diverse fields that comprise plant biology to address Grand Challenges in new ways, to stimulate and facilitate cross-disciplinary research, to promote biology and computer science research interactions, and to train the next generation of scientists on the use of cyberinfrastructure in research and education. Meeting humanity's projected demands for agricultural and forest products and the expectation that natural ecosystems be managed sustainably will require synergies from the application of information technologies. The iPlant cyberinfrastructure design is based on an unprecedented period of research community input, and leverages developments in high-performance computing, data storage, and cyberinfrastructure for the physical sciences. iPlant is an open-source project with application programming interfaces that allow the community to extend the infrastructure to meet its needs. iPlant is sponsoring community-driven workshops addressing specific scientific questions via analysis tool integration and hypothesis testing. These workshops teach researchers how to add bioinformatics tools and/or datasets into the iPlant cyberinfrastructure enabling plant scientists to perform complex analyses on large datasets without the need to master the command-line or high-performance computational services.
- Kattge, J., Diaz, S., Lavorel, S., Prentice, C., Leadley, P., Boenisch, G., Garnier, E., Westoby, M., Reich, P. B., Wright, I. J., Cornelissen, J., Violle, C., Harrison, S. P., van, B., Reichstein, M., Enquist, B. J., Soudzilovskaia, N. A., Ackerly, D. D., Anand, M., , Atkin, O., et al. (2011). TRY - a global database of plant traits. GLOBAL CHANGE BIOLOGY, 17(9), 2905-2935.
- Kattge, J., Díaz, S., Lavorel, S., Prentice, I. C., Leadley, P., Bönisch, G., Garnier, E., Westoby, M., Reich, P. B., Wright, I. J., Cornelissen, J. H., Violle, C., Harrison, S. P., Bodegom, P. V., Reichstein, M., Enquist, B. J., Soudzilovskaia, N. A., Ackerly, D. D., Anand, M., , Atkin, O., et al. (2011). TRY - a global database of plant traits. Global Change Biology, 17(9), 2905-2935.More infoAbstract: Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants and their organs - determine how primary producers respond to environmental factors, affect other trophic levels, influence ecosystem processes and services and provide a link from species richness to ecosystem functional diversity. Trait data thus represent the raw material for a wide range of research from evolutionary biology, community and functional ecology to biogeography. Here we present the global database initiative named TRY, which has united a wide range of the plant trait research community worldwide and gained an unprecedented buy-in of trait data: so far 93 trait databases have been contributed. The data repository currently contains almost three million trait entries for 69000 out of the world's 300000 plant species, with a focus on 52 groups of traits characterizing the vegetative and regeneration stages of the plant life cycle, including growth, dispersal, establishment and persistence. A first data analysis shows that most plant traits are approximately log-normally distributed, with widely differing ranges of variation across traits. Most trait variation is between species (interspecific), but significant intraspecific variation is also documented, up to 40% of the overall variation. Plant functional types (PFTs), as commonly used in vegetation models, capture a substantial fraction of the observed variation - but for several traits most variation occurs within PFTs, up to 75% of the overall variation. In the context of vegetation models these traits would better be represented by state variables rather than fixed parameter values. The improved availability of plant trait data in the unified global database is expected to support a paradigm shift from species to trait-based ecology, offer new opportunities for synthetic plant trait research and enable a more realistic and empirically grounded representation of terrestrial vegetation in Earth system models. © 2011 Blackwell Publishing Ltd.
- Kerkhoff, A. J., & Enquist, B. J. (2011). The implications of scaling approaches for understanding resilience and reorganization in ecosystems. BIOSCIENCE, 57(6), 489-499.
- Li, Y. M., Dlugosch, K. M., & Enquist, B. J. (2015). Novel spatial analysis methods reveal scale‐dependent spread and infer limiting factors of invasion by Sahara mustard. Ecography, 38(3), 311–320.
- McCarthy, M. C., & Enquist, B. J. (2011). Consistency between an allometric approach and optimal partitioning theory in global patterns of plant biomass allocation. FUNCTIONAL ECOLOGY, 21(4), 713-720.More info1. Optimal partitioning theory (OPT) suggests that plants should allocate biomass to the organ that acquires the most limiting resource. An implied assumption of this is that there are trade-offs in allocation between leaf, stem and root functions.
- Moles, A. T., Wallis, I. R., Foley, W. J., Warton, D. I., Stegen, J. C., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnaes, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magana-Rodriguez, B., Moore, B. D., Peri, P. L., , Poulsen, J. R., et al. (2011). Putting plant resistance traits on the map: a test of the idea that plants are better defended at lower latitudes. NEW PHYTOLOGIST, 191(3), 777-788.
- Moles, A. T., Wallis, I. R., Foley, W. J., Warton, D. I., Stegen, J. C., Bisigato, A. J., Cella-Pizarro, L., Clark, C. J., Cohen, P. S., Cornwell, W. K., Edwards, W., Ejrnæs, R., Gonzales-Ojeda, T., Graae, B. J., Hay, G., Lumbwe, F. C., Magaña-Rodríguez, B., Moore, B. D., Peri, P. L., , Poulsen, J. R., et al. (2011). Putting plant resistance traits on the map: A test of the idea that plants are better defended at lower latitudes. New Phytologist, 191(3), 777-788.More infoPMID: 21539574;Abstract: It has long been believed that plant species from the tropics have higher levels of traits associated with resistance to herbivores than do species from higher latitudes. A meta-analysis recently showed that the published literature does not support this theory. However, the idea has never been tested using data gathered with consistent methods from a wide range of latitudes. We quantified the relationship between latitude and a broad range of chemical and physical traits across 301 species from 75 sites world-wide. Six putative resistance traits, including tannins, the concentration of lipids (an indicator of oils, waxes and resins), and leaf toughness were greater in high-latitude species. Six traits, including cyanide production and the presence of spines, were unrelated to latitude. Only ash content (an indicator of inorganic substances such as calcium oxalates and phytoliths) and the properties of species with delayed greening were higher in the tropics. Our results do not support the hypothesis that tropical plants have higher levels of resistance traits than do plants from higher latitudes. If anything, plants have higher resistance toward the poles. The greater resistance traits of high-latitude species might be explained by the greater cost of losing a given amount of leaf tissue in low-productivity environments. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.
- Riveros, A. J., & Enquist, B. J. (2011). Metabolic scaling in insects supports the predictions of the WBE model. Journal of Insect Physiology, 57(6), 688-693.More infoPMID: 21296084;Abstract: The functional association between body size and metabolic rate (BS-MR) is one of the most intriguing issues in ecological physiology. An average scaling exponent of 3/4 is broadly observed across animal and plant taxa. The numerical value of 3/4 is theoretically predicted under the optimized version of West, Brown, and Enquist's vascular resource supply network model. Insects, however, have recently been proposed to express a numerically different scaling exponent and thus application of the WBE network model to insects has been rejected. Here, we re-analyze whether such variation is indeed supported by a global deviation across all insect taxa at the order and family levels to assess if specific taxa influence insect metabolic scaling. We show that a previous reported deviation is largely due to the effect of a single insect family (Termitidae). We conclude that the BS-MR relationship in insects broadly supports the core predictions of the WBE model. We suggest that the deviation observed within the termites warrants further investigation and may be due to either difficulty in accurately measuring termite metabolism and/or particularities of their life history. Future work on allometric scaling should assess the nature of variation around the central tendencies in scaling exponents in order to test if this variation is consistent with core assumptions and predictions of the WBE model that stem by relaxing its secondary optimizing assumptions that lead to the 3/4 exponent. © 2011 Elsevier Ltd.
- Simova, I., Storch, D., Keil, P., Boyle, B., Phillips, O. L., & Enquist, B. J. (2011). Global species-energy relationship in forest plots: role of abundance, temperature and species climatic tolerances. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 20(6), 842-856.
- Stark, S. C., Bentley, L. P., & Enquist, B. J. (2011). Response to Coomes & Allen (2009)'Testing the metabolic scaling theory of tree growth'. JOURNAL OF ECOLOGY, 99(3), 741-747.
- Stark, S. C., Bentley, L. P., & Enquist, B. J. (2011). Response to Coomes & Allen (2009)'Testing the metabolic scaling theory of tree growth'. Journal of Ecology, 99(3), 741-747.More infoAbstract: Coomes & Allen (2009) propose a new statistical method to test the Metabolic Scaling Theory prediction for tree growth rate size scaling (scaling constant α=1/3) presented in Enquist (1999). This method finds values of the scaling constant that yield standardized major axis (SMA) slopes of one in a comparison of allometrically transformed diameter census data. This SMA 'slope-of-one' method produces results that contrast with those generated by maximum-likelihood estimation (MLE; Russo, Wiser & Coomes 2007; Coomes & Allen 2009). We hypothesize that the SMA slope-of-one method is inappropriate for this application because it assumes, unrealistically, that there is no biological or error variance in tree growth size scaling. To test our hypothesis, we simulate 'allometric' tree growth with biological and error variance in parameters and measurements. We find that the SMA slope-of-one method is sensitive to the amount of biological and error variance and consistently returns biassed parameter estimates, while the MLE method displays relatively little bias, particularly at larger sample sizes. Synthesis. The conclusions of Coomes & Allen (2009) should be reconsidered in the light of our findings. Investigations of tree growth rate size scaling must consider the influence of biological and error variance in model-fitting procedures to ultimately unravel the effects of tree architecture and ecological factors on patterns of size-dependent growth. © 2010 The Authors. Journal of Ecology © 2010 British Ecological Society.
- Stegen, J. C., Swenson, N. G., Enquist, B. J., White, E. P., Phillips, O. L., Jorgensen, P. M., Weiser, M. D., Monteagudo, M. A., & Vargas, P. N. (2011). Variation in above-ground forest biomass across broad climatic gradients. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 20(5), 744-754.
- Stegen, J. C., Swenson, N. G., Enquist, B. J., White, E. P., Phillips, O. L., Jørgensen, P. M., Weiser, M. D., Mendoza, A. M., & Vargas, P. N. (2011). Variation in above-ground forest biomass across broad climatic gradients. Global Ecology and Biogeography, 20(5), 744-754.More infoAbstract: Aim An understanding of the relationship between forest biomass and climate is needed to predict the impacts of climate change on carbon stores. Biomass patterns have been characterized at geographically or climatically restricted scales, making it unclear if biomass is limited by climate in any general way at continental to global scales. Using a dataset spanning multiple climatic regions we evaluate the generality of published biomass-climate correlations. We also combine metabolic theory and hydraulic limits to plant growth to first derive and then test predictions for how forest biomass should vary with maximum individual tree biomass and the ecosystem water deficit. Location Temperate forests and dry, moist and wet tropical forests across North, Central and South America. Methods A forest biomass model was derived from allometric functions and power-law size distributions. Biomass and climate were correlated using extensive forest plot (276 0.1-ha plots), wood density and climate datasets. Climate variables included mean annual temperature, annual precipitation, their ratio, precipitation of the driest quarter, potential and actual evapotranspiration, and the ecosystem water deficit. The water deficit uniquely summarizes water balance by integrating water inputs from precipitation with water losses due to solar energy. Results Climate generally explained little variation in forest biomass, and mixed support was found for published biomass-climate relationships. Our theory indicated that maximum individual biomass governs forest biomass and is constrained by water deficit. Indeed, forest biomass was tightly coupled to maximum individual biomass and the upper bound of maximum individual biomass declined steeply with water deficit. Water deficit similarly constrained the upper bound of forest biomass, with most forests below the constraint. Main conclusions The results suggest that: (1) biomass-climate models developed at restricted geographic/climatic scales may not hold at broader scales; (2) maximum individual biomass is strongly related to forest biomass, suggesting that process-based models should focus on maximum individual biomass; (3) the ecosystem water deficit constrains biomass, but realized biomass often falls below the constraint; such that (4) biomass is not strongly limited by climate in most forests so that forest biomass may not predictably respond to changes in mean climate. © 2011 Blackwell Publishing Ltd.
- Swenson, N. G., Enquist, B. J., Pither, J., Thompson, J., & Zimmerman, J. K. (2011). The problem and promise of scale dependency in community phylogenetics. ECOLOGY, 87(10), 2418-2424.
- West, G. B., Enquist, B. J., & Brown, J. H. (2011). A general quantitative theory of forest structure and dynamics. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(17), 7040-7045.
- Šímová, I., Storch, D., Keil, P., Boyle, B., Phillips, O. L., & Enquist, B. J. (2011). Global species-energy relationship in forest plots: Role of abundance, temperature and species climatic tolerances. Global Ecology and Biogeography, 20(6), 842-856.More infoAbstract: Aim To evaluate the strength of evidence for hypotheses explaining the relationship between climate and species richness in forest plots. We focused on the effect of energy availability which has been hypothesized to influence species richness: (1) via the effect of productivity on the total number of individuals (the more individuals hypothesis, MIH); (2) through the effect of temperature on metabolic rate (metabolic theory of biodiversity, MTB); or (3) by imposing climatic limits on species distributions. Location Global. Methods We utilized a unique 'Gentry-style' 370 forest plots data set comprising tree counts and individual stem measurements, covering tropical and temperate forests across all six forested continents. We analysed variation in plot species richness and species richness controlled for the number of individuals by using rarefaction. Ordinary least squares (OLS) regression and spatial regressions were used to explore the relative performance of different sets of environmental variables. Results Species richness patterns do not differ whether we use raw number of species or number of species controlled for number of individuals, indicating that number of individuals is not the proximate driver of species richness. Productivity-related variables (actual evapotranspiration, net primary productivity, normalized difference vegetation index) perform relatively poorly as correlates of tree species richness. The best predictors of species richness consistently include the minimum temperature and precipitation values together with the annual means of these variables. Main conclusion Across the world's forests there is no evidence to support the MIH, and a very limited evidence for a prominent role of productivity as a driver of species richness patterns. The role of temperature is much more important, although this effect is more complex than originally assumed by the MTB. Variation in forest plot diversity appears to be mostly affected by variation in the minimum climatic values. This is consistent with the 'climatic tolerance hypothesis' that climatic extremes have acted as a strong constraint on species distribution and diversity. © 2011 Blackwell Publishing Ltd.
- Elser, J. J., Fagan, W. F., Kerkhoff, A. J., Swenson, N. G., & Enquist, B. J. (2010). Biological stoichiometry of plant production: Metabolism, scaling and ecological response to global change. New Phytologist, 186(3), 593-608.More infoPMID: 20298486;Abstract: Biological stoichiometry theory considers the balance of multiple chemical elements in living systems, whereas metabolic scaling theory considers how size affects metabolic properties from cells to ecosystems. We review recent developments integrating biological stoichiometry and metabolic scaling theories in the context of plant ecology and global change. Although vascular plants exhibit wide variation in foliar carbon: nitrogen: phosphorus ratios, they exhibit a higher degree of 'stoichiometric homeostasis' than previously appreciated. Thus, terrestrial carbon: nitrogen: phosphorus stoichiometry will reflect the effects of adjustment to local growth conditions as well as species' replacements. Plant stoichiometry exhibits size scaling, as foliar nutrient concentration decreases with increasing plant size, especially for phosphorus. Thus, small plants have lower nitrogen: phosphorus ratios. Furthermore, foliar nutrient concentration is reflected in other tissues (root, reproductive, support), permitting the development of empirical models of production that scale from tissue to whole-plant levels. Plant stoichiometry exhibits large-scale macroecological patterns, including stronger latitudinal trends and environmental correlations for phosphorus concentration (relative to nitrogen) and a positive correlation between nutrient concentrations and geographic range size. Given this emerging knowledge of how plant nutrients respond to environmental variables and are connected to size, the effects of global change factors (such as carbon dioxide, temperature, nitrogen deposition) can be better understood. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).
- Elser, J. J., Fagan, W. F., Kerkhoff, A. J., Swenson, N. G., & Enquist, B. J. (2010). Biological stoichiometry of plant production: metabolism, scaling and ecological response to global change. NEW PHYTOLOGIST, 186(3), 593-608.
- Savage, V. M., Bentley, L. P., Enquist, B. J., Sperry, J. S., Smith, D. D., Reich, P. B., & Allmen, E. V. (2010). Hydraulic trade-offs and space filling enable better predictions of vascular structure and function in plants. Proceedings of the National Academy of Sciences of the United States of America, 107(52), 22722-22727.More infoPMID: 21149696;PMCID: PMC3012458;Abstract: Plant vascular networks are central to botanical form, function, and diversity. Here, we develop a theory for plant network scaling that is based on optimal space filling by the vascular system along with trade-offs between hydraulic safety and efficiency. Including these evolutionary drivers leads to predictions for sap flow, the taper of the radii of xylem conduits from trunk to terminal twig, and how the frequency of xylem conduits varies with conduit radius. To test our predictions, we use comprehensive empirical measurements of maple, oak, and pine trees and complementary literature data that we obtained for a wide range of tree species. This robust intra- and interspecific assessment of our botanical network model indicates that the central tendency of observed scaling properties supports our predictions much better than the West, Brown, and Enquist (WBE) or pipe models. Consequently, our model is a more accurate description of vascular architecture than what is given by existing network models and should be used as a baseline to understand and to predict the scaling of individual plants to whole forests. In addition, our model is flexible enough to allow the quantification of species variation around rules for network design. These results suggest that the evolutionary drivers that we propose have been fundamental in determining how physiological processes scale within and across plant species.
- Conlisk, E., Conlisk, J., Enquist, B., Thompson, J., & Harte, J. (2009). Improved abundance prediction from presence-absence data. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 18(1), 1-10.
- Enquist, B. J., West, G. B., & Brown, J. H. (2009). Extensions and evaluations of a general quantitative theory of forest structure and dynamics. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 106(17), 7046-7051.
- Enquist, B. J., West, G. B., & Brown, J. H. (2009). Extensions and evaluations of a general quantitative theory of forest structure and dynamics. Proceedings of the National Academy of Sciences of the United States of America, 106(17), 7046-51.More infoHere, we present the second part of a quantitative theory for the structure and dynamics of forests under demographic and resource steady state. The theory is based on individual-level allometric scaling relations for how trees use resources, fill space, and grow. These scale up to determine emergent properties of diverse forests, including size-frequency distributions, spacing relations, canopy configurations, mortality rates, population dynamics, successional dynamics, and resource flux rates. The theory uniquely makes quantitative predictions for both stand-level scaling exponents and normalizations. We evaluate these predictions by compiling and analyzing macroecological datasets from several tropical forests. The close match between theoretical predictions and data suggests that forests are organized by a set of very general scaling rules. Our mechanistic theory is based on allometric scaling relations, is complementary to "demographic theory," but is fundamentally different in approach. It provides a quantitative baseline for understanding deviations from predictions due to other factors, including disturbance, variation in branching architecture, asymmetric competition, resource limitation, and other sources of mortality, which are not included in the deliberately simplified theory. The theory should apply to a wide range of forests despite large differences in abiotic environment, species diversity, and taxonomic and functional composition.
- McCarthy, M. C., Enquist, B. J., & Kerkhoff, A. J. (2009). Organ partitioning and distribution across the seed plants: Assessing the relative importance of phylogeny and function. INTERNATIONAL JOURNAL OF PLANT SCIENCES, 168(5), 751-761.
- Morlon, H., White, E. P., Etienne, R. S., Green, J. L., Ostling, A., Alonso, D., Enquist, B. J., He, F., Hurlbert, A., Magurran, A. E., Maurer, B. A., McGill, B. J., Olff, H., Storch, D., & Zillio, T. (2009). Taking species abundance distributions beyond individuals. ECOLOGY LETTERS, 12(6), 488-501.
- Morlon, H., White, E. P., Etienne, R. S., Green, J. L., Ostling, A., Alonso, D., Enquist, B. J., He, F., Hurlbert, A., Magurran, A. E., Maurer, B. A., McGill, B. J., Olff, H., Storch, D., & Zillio, T. (2009). Taking species abundance distributions beyond individuals. Ecology letters, 12(6), 488-501.More infoThe species abundance distribution (SAD) is one of the few universal patterns in ecology. Research on this fundamental distribution has primarily focused on the study of numerical counts, irrespective of the traits of individuals. Here we show that considering a set of Generalized Species Abundance Distributions (GSADs) encompassing several abundance measures, such as numerical abundance, biomass and resource use, can provide novel insights into the structure of ecological communities and the forces that organize them. We use a taxonomically diverse combination of macroecological data sets to investigate the similarities and differences between GSADs. We then use probability theory to explore, under parsimonious assumptions, theoretical linkages among them. Our study suggests that examining different GSADs simultaneously in natural systems may help with assessing determinants of community structure. Broadening SADs to encompass multiple abundance measures opens novel perspectives in biodiversity research and warrants future empirical and theoretical developments.
- Price, C. A., & Enquist, B. J. (2009). Comment on Coomes et al. 'Scaling of xylem vessels and veins within the leaves of oak species'. Biology letters, 5(3), 380; author reply 381-2.
- Stegen, J. C., Enquist, B. J., & Ferriere, R. (2009). Advancing the metabolic theory of biodiversity. Ecology letters, 12(10), 1001-15.More infoA component of metabolic scaling theory has worked towards understanding the influence of metabolism over the generation and maintenance of biodiversity. Specific models within this 'metabolic theory of biodiversity' (MTB) have addressed temperature gradients in speciation rate and species richness, but the scope of MTB has been questioned because of empirical departures from model predictions. In this study, we first show that a generalized MTB is not inconsistent with empirical patterns and subsequently implement an eco-evolutionary MTB which has thus far only been discussed qualitatively. More specifically, we combine a functional trait (body mass) approach and an environmental gradient (temperature) with a dynamic eco-evolutionary model that builds on the current MTB. Our approach uniquely accounts for feedbacks between ecological interactions (size-dependent competition and predation) and evolutionary rates (speciation and extinction). We investigate a simple example in which temperature influences mutation rate, and show that this single effect leads to dynamic temperature gradients in macroevolutionary rates and community structure. Early in community evolution, temperature strongly influences speciation and both speciation and extinction strongly influence species richness. Through time, niche structure evolves, speciation and extinction rates fall, and species richness becomes increasingly independent of temperature. However, significant temperature-richness gradients may persist within emergent functional (trophic) groups, especially when niche breadths are wide. Thus, there is a strong signal of both history and ecological interactions on patterns of species richness across temperature gradients. More generally, the successful implementation of an eco-evolutionary MTB opens the perspective that a process-based MTB can continue to emerge through further development of metabolic models that are explicit in terms of functional traits and environmental gradients.
- Swenson, N. G., & Enquist, B. J. (2009). Opposing assembly mechanisms in a neotropical dry forest: implications for phylogenetic and functional community ecology. Ecology, 90(8), 2161-70.More infoSpecies diversity is promoted and maintained by ecological and evolutionary processes operating on species attributes through space and time. The degree to which variability in species function regulates distribution and promotes coexistence of species has been debated. Previous work has attempted to quantify the relative importance of species function by using phylogenetic relatedness as a proxy for functional similarity. The key assumption of this approach is that function is phylogenetically conserved. If this assumption is supported, then the phylogenetic dispersion in a community should mirror the functional dispersion. Here we quantify functional trait dispersion along several key axes of tree life-history variation and on multiple spatial scales in a Neotropical dry-forest community. We next compare these results to previously reported patterns of phylogenetic dispersion in this same forest. We find that, at small spatial scales, coexisting species are typically more functionally clustered than expected, but traits related to adult and regeneration niches are overdispersed. This outcome was repeated when the analyses were stratified by size class. Some of the trait dispersion results stand in contrast to the previously reported phylogenetic dispersion results. In order to address this inconsistency we examined the strength of phylogenetic signal in traits at different depths in the phylogeny. We argue that: (1) while phylogenetic relatedness may be a good general multivariate proxy for ecological similarity, it may have a reduced capacity to depict the functional mechanisms behind species coexistence when coexisting species simultaneously converge and diverge in function; and (2) the previously used metric of phylogenetic signal provided erroneous inferences about trait dispersion when married with patterns of phylogenetic dispersion.
- West, G. B., Enquist, B. J., & Brown, J. H. (2009). A general quantitative theory of forest structure and dynamics. Proceedings of the National Academy of Sciences of the United States of America, 106(17), 7040-5.More infoWe present the first part of a quantitative theory for the structure and dynamics of forests at demographic and resource steady state. The theory uses allometric scaling relations, based on metabolism and biomechanics, to quantify how trees use resources, fill space, and grow. These individual-level traits and properties scale up to predict emergent properties of forest stands, including size-frequency distributions, spacing relations, resource flux rates, and canopy configurations. Two insights emerge from this analysis: (i) The size structure and spatial arrangement of trees in the entire forest are emergent manifestations of the way that functionally invariant xylem elements are bundled together to conduct water and nutrients up from the trunks, through the branches, to the leaves of individual trees. (ii) Geometric and dynamic properties of trees in a forest and branches in trees scale identically, so that the entire forest can be described mathematically and behaves structurally and functionally like a scaled version of the branching networks in the largest tree. This quantitative framework uses a small number of parameters to predict numerous structural and dynamical properties of idealized forests.
- Bryant, J. A., Lamanna, C., Morlon, H., Kerkhoff, A. J., Enquist, B. J., & Green, J. L. (2008). Colloquium paper: microbes on mountainsides: contrasting elevational patterns of bacterial and plant diversity. Proceedings of the National Academy of Sciences of the United States of America, 105 Suppl 1, 11505-11.More infoThe study of elevational diversity gradients dates back to the foundation of biogeography. Although elevational patterns of plant and animal diversity have been studied for centuries, such patterns have not been reported for microorganisms and remain poorly understood. Here, in an effort to assess the generality of elevational diversity patterns, we examined soil bacterial and plant diversity along an elevation gradient. To gain insight into the forces that structure these patterns, we adopted a multifaceted approach to incorporate information about the structure, diversity, and spatial turnover of montane communities in a phylogenetic context. We found that observed patterns of plant and bacterial diversity were fundamentally different. While bacterial taxon richness and phylogenetic diversity decreased monotonically from the lowest to highest elevations, plants followed a unimodal pattern, with a peak in richness and phylogenetic diversity at mid-elevations. At all elevations bacterial communities had a tendency to be phylogenetically clustered, containing closely related taxa. In contrast, plant communities did not exhibit a uniform phylogenetic structure across the gradient: they became more overdispersed with increasing elevation, containing distantly related taxa. Finally, a metric of phylogenetic beta-diversity showed that bacterial lineages were not randomly distributed, but rather exhibited significant spatial structure across the gradient, whereas plant lineages did not exhibit a significant phylogenetic signal. Quantifying the influence of sample scale in intertaxonomic comparisons remains a challenge. Nevertheless, our findings suggest that the forces structuring microorganism and macroorganism communities along elevational gradients differ.
- Poore, R. E., Lamanna, C. A., Ebersole, J. J., & Enquist, B. J. (2008). CONTROLS ON RADIAL GROWTH OF MOUNTAIN BIG SAGEBRUSH AND IMPLICATIONS FOR CLIMATE CHANGE. WESTERN NORTH AMERICAN NATURALIST, 69(4), 556-562.
- Swenson, N. G., Enquist, B. J., Thompson, J., & Zimmerman, J. K. (2008). The influence of spatial and size scale on phylogenetic relatedness in tropical forest communities. ECOLOGY, 88(7), 1770-1780.
- Weiser, M. D., Enquist, B. J., Boyle, B., Killeen, T. J., Jorgensen, P. M., Fonseca, G., Jennings, M. D., Kerkhoff, A. J., Lacher, T. E., Monteagudo, A., Vargas, M. P., Phillips, O. L., Swenson, N. G., & Martinez, R. V. (2008). Latitudinal patterns of range size and species richness of New World woody plants. GLOBAL ECOLOGY AND BIOGEOGRAPHY, 16(5), 679-688.
- White, E. P., Enquist, B. J., & Green, J. L. (2008). On estimating the exponent of power-law frequency distributions. Ecology, 89(4), 905-12.More infoPower-law frequency distributions characterize a wide array of natural phenomena. In ecology, biology, and many physical and social sciences, the exponents of these power laws are estimated to draw inference about the processes underlying the phenomenon, to test theoretical models, and to scale up from local observations to global patterns. Therefore, it is essential that these exponents be estimated accurately. Unfortunately, the binning-based methods traditionally used in ecology and other disciplines perform quite poorly. Here we discuss more sophisticated methods for fitting these exponents based on cumulative distribution functions and maximum likelihood estimation. We illustrate their superior performance at estimating known exponents and provide details on how and when ecologists should use them. Our results confirm that maximum likelihood estimation outperforms other methods in both accuracy and precision. Because of the use of biased statistical methods for estimating the exponent, the conclusions of several recently published papers should be revisited.
- Bryant, J. A., Lamanna, C., Morlon, H., Kerkhoff, A. J., Enquist, B. J., & Green, J. L. (2007). Microbes on mountainsides: Contrasting elevational patterns of bacterial and plant diversity. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 105, 11505-11511.
- Cable, J. M., Enquist, B. J., & Moses, M. E. (2007). The Allometry of Host- Pathogen Interactions. PLOS ONE, 2(11).
- Conlisk, E., Bloxham, M., Conlisk, J., Enquist, B., & Harte, J. (2007). A new class of models of spatial distribution. ECOLOGICAL MONOGRAPHS, 77(2), 269-284.
- Enquist, B. J., & Stark, S. C. (2007). Follow Thompson's map to turn biology from a science into a Science. NATURE, 446(7136), 611-611.
- Enquist, B. J., & Stark, S. C. (2007). Follow Thompson's map to turn biology from a science into a Science. Nature, 446(7136), 611.
- Enquist, B. J., Allen, A. P., Brown, J. H., Gillooly, J. F., Kerkhoff, A. J., Niklas, K. J., Price, C. A., & West, G. B. (2007). Biological scaling: does the exception prove the rule?. Nature, 445(7127), E9-10; discussion E10-1.More infoReich et al. report that the whole-plant respiration rate, R, in seedlings scales linearly with plant mass, M, so that R=C(R)M(theta) when theta approximately 1, in which c(R) is the scaling normalization and theta is the scaling exponent. They also state that because nitrogen concentration (N) is correlated with c(R), variation in N is a better predictor of R than M would be. Reich et al. and Hedin incorrectly claim that these "universal" findings question the central tenet of metabolic scaling theory, which they interpret as predicting theta = (3/4), irrespective of the size of the plant. Here we show that these conclusions misrepresent metabolic scaling theory and that their results are actually consistent with this theory.
- Enquist, B. J., Kerkhoff, A. J., Stark, S. C., Swenson, N. G., McCarthy, M. C., & Price, C. A. (2007). A general integrative model for scaling plant growth, carbon flux, and functional trait spectra. NATURE, 449(7159), 218-222.
- Enquist, B. J., Kerkhoff, A. J., Stark, S. C., Swenson, N. G., McCarthy, M. C., & Price, C. A. (2007). A general integrative model for scaling plant growth, carbon flux, and functional trait spectra. Nature, 449(7159), 218-22.More infoLinking functional traits to plant growth is critical for scaling attributes of organisms to the dynamics of ecosystems and for understanding how selection shapes integrated botanical phenotypes. However, a general mechanistic theory showing how traits specifically influence carbon and biomass flux within and across plants is needed. Building on foundational work on relative growth rate, recent work on functional trait spectra, and metabolic scaling theory, here we derive a generalized trait-based model of plant growth. In agreement with a wide variety of empirical data, our model uniquely predicts how key functional traits interact to regulate variation in relative growth rate, the allometric growth normalizations for both angiosperms and gymnosperms, and the quantitative form of several functional trait spectra relationships. The model also provides a general quantitative framework to incorporate additional leaf-level trait scaling relationships and hence to unite functional trait spectra with theories of relative growth rate, and metabolic scaling. We apply the model to calculate carbon use efficiency. This often ignored trait, which may influence variation in relative growth rate, appears to vary directionally across geographic gradients. Together, our results show how both quantitative plant traits and the geometry of vascular transport networks can be merged into a common scaling theory. Our model provides a framework for predicting not only how traits covary within an integrated allometric phenotype but also how trait variation mechanistically influences plant growth and carbon flux within and across diverse ecosystems.
- Marquet, P. A., Allen, A. P., Brown, J. H., Dunne, J. A., Enquist, B. J., Gillooly, J. F., Gowaty, P. A., Green, J. L., Harte, J., Hubbell, S. P., O'Dwyer, J., Okie, J. G., Ostling, A., Ritchie, M., Storch, D., & West, G. B. (2007). On Theory in Ecology. BIOSCIENCE, 64(8), 701-710.
- McGill, B. J., Etienne, R. S., Gray, J. S., Alonso, D., Anderson, M. J., Benecha, H. K., Dornelas, M., Enquist, B. J., Green, J. L., He, F., Hurlbert, A. H., Magurran, A. E., Marquet, P. A., Maurer, B. A., Ostling, A., Soykan, C. U., Ugland, K. I., & White, E. P. (2007). Species abundance distributions: moving beyond single prediction theories to integration within an ecological framework. ECOLOGY LETTERS, 10(10), 995-1015.
- McGill, B. J., Etienne, R. S., Gray, J. S., Alonso, D., Anderson, M. J., Benecha, H. K., Dornelas, M., Enquist, B. J., Green, J. L., He, F., Hurlbert, A. H., Magurran, A. E., Marquet, P. A., Maurer, B. A., Ostling, A., Soykan, C. U., Ugland, K. I., & White, E. P. (2007). Species abundance distributions: moving beyond single prediction theories to integration within an ecological framework. Ecology letters, 10(10), 995-1015.More infoSpecies abundance distributions (SADs) follow one of ecology's oldest and most universal laws--every community shows a hollow curve or hyperbolic shape on a histogram with many rare species and just a few common species. Here, we review theoretical, empirical and statistical developments in the study of SADs. Several key points emerge. (i) Literally dozens of models have been proposed to explain the hollow curve. Unfortunately, very few models are ever rejected, primarily because few theories make any predictions beyond the hollow-curve SAD itself. (ii) Interesting work has been performed both empirically and theoretically, which goes beyond the hollow-curve prediction to provide a rich variety of information about how SADs behave. These include the study of SADs along environmental gradients and theories that integrate SADs with other biodiversity patterns. Central to this body of work is an effort to move beyond treating the SAD in isolation and to integrate the SAD into its ecological context to enable making many predictions. (iii) Moving forward will entail understanding how sampling and scale affect SADs and developing statistical tools for describing and comparing SADs. We are optimistic that SADs can provide significant insights into basic and applied ecological science.
- Price, C. A., & Enquist, B. J. (2007). Scaling mass and morphology in leaves: An extension of the WBE model. ECOLOGY, 88(5), 1132-1141.
- Price, C. A., & Enquist, B. J. (2007). Scaling mass and morphology in leaves: an extension of the WBE model. Ecology, 88(5), 1132-41.More infoRecent advances in metabolic scaling theory have highlighted the importance of exchange surfaces and vascular network geometry in understanding the integration and scaling of whole-plant form and function. Additional work on leaf form and function has also highlighted general scaling relationships for many leaf traits. However, it is unclear if a common theoretical framework can reveal the general rules underlying much of the variation observed in scaling relationships at the whole-plant and leaf level. Here we present an extension of the general model introduced by G. B. West, J. H. Brown, and B. J. Enquist that has previously been applied to scaling phenomena for whole plants to predict scaling relationships in leaves. Specifically, the model shows how the exponents that describe the scaling of leaf surface area, length, and petiole diameter should change with increasing leaf mass (or with one another) and with variation in leaf dimensionality. The predictions of the model are tested and found to be in general agreement with a large data set of leaves collected from both temperate and arid sites. Our results demonstrate that a general model based on the scaling properties of biological distribution networks can also be successfully applied to understand the diversity of leaf form and function.
- Price, C. A., Enquist, B. J., & Savage, V. M. (2007). A general model for allometric covariation in botanical form and function. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 104(32), 13204-13209.
- Price, C. A., Enquist, B. J., & Savage, V. M. (2007). A general model for allometric covariation in botanical form and function. Proceedings of the National Academy of Sciences of the United States of America, 104(32), 13204-9.More infoThe West, Brown, and Enquist (WBE) theory for the origin of allometric scaling laws is centered on the idea that the geometry of the vascular network governs how a suite of organismal traits covary with each other and, ultimately, how they scale with organism size. This core assumption has been combined with other secondary assumptions based on physiological constraints, such as minimizing the scaling of transport and biomechanical costs while maximally filling a volume. Together, these assumptions give predictions for specific "quarter-power" scaling exponents in biology. Here we provide a strong test of the core assumption of WBE by examining how well it holds when the secondary assumptions have been relaxed. Our relaxed version of WBE predicts that allometric exponents are highly constrained and covary according to specific quantitative functions. To test this core prediction, we assembled several botanical data sets with measures of the allometry of morphological traits. A wide variety of plant taxa appear to obey the predictions of the model. Our results (i) underscore the importance of network geometry in governing the variability and central tendency of biological exponents, (ii) support the hypothesis that selection has primarily acted to minimize the scaling of hydrodynamic resistance, and (iii) suggest that additional selection pressures for alternative branching geometries govern much of the observed covariation in biological scaling exponents. Understanding how selection shapes hierarchical branching networks provides a general framework for understanding the origin and covariation of many allometric traits within a complex integrated phenotype.
- Savage, V. M., Enquist, B. J., & West, G. B. (2007). Comment on 'A critical understanding of the fractal model of metabolic scaling'. JOURNAL OF EXPERIMENTAL BIOLOGY, 210(21), 3873-3874.
- Swenson, N. G., & Enquist, B. J. (2007). Ecological and evolutionary determinants of a key plant functional trait: Wood density and its community-wide variation across latitude and elevation. AMERICAN JOURNAL OF BOTANY, 94(3), 451-459.
- Swenson, N. G., & Enquist, B. J. (2007). Opposing assembly mechanisms in a Neotropical dry forest: implications for phylogenetic and functional community ecology. ECOLOGY, 90(8), 2161-2170.
- Swenson, N. G., & Enquist, B. J. (2007). The relationship between stem and branch wood specific gravity and the ability of each measure to predict leaf area. AMERICAN JOURNAL OF BOTANY, 95(4), 516-519.
- White, E. P., Enquist, B. J., & Green, J. L. (2007). On estimating the exponent of power-law frequency distributions. ECOLOGY, 89(4), 905-912.
- White, E. P., Ernest, S. K., Kerkhoff, A. J., & Enquist, B. J. (2007). Relationships between body size and abundance in ecology. Trends in ecology & evolution, 22(6), 323-30.More infoBody size is perhaps the most fundamental property of an organism and is related to many biological traits, including abundance. The relationship between abundance and body size has been extensively studied in an attempt to quantify the form of the relationship and to understand the processes that generate it. However, progress has been impeded by the under appreciated fact that there are four distinct, but interrelated, relationships between size and abundance that are often confused in the literature. Here, we review and distinguish between these four patterns, and discuss the linkages between them. We argue that a synthetic understanding of size-abundance relationships will result from more detailed analyses of individual patterns and from careful consideration of how and why the patterns are related.
- White, E. P., Ernest, S., Kerkhoff, A. J., & Enquist, B. J. (2007). Relationships between body size and abundance in ecology. TRENDS IN ECOLOGY & EVOLUTION, 22(6), 323-330.
- Kerkhoff, A. J., & Enquist, B. J. (2006). Ecosystem allometry: the scaling of nutrient stocks and primary productivity across plant communities. Ecology letters, 9(4), 419-27.More infoA principal challenge in ecology is to integrate physiological function (e.g. photosynthesis) across a collection of individuals (e.g. plants of different species) to understand the functioning of the entire ensemble (e.g. primary productivity). The control that organism size exerts over physiological and ecological function suggests that allometry could be a powerful tool for scaling ecological processes across levels of organization. Here we use individual plant allometries to predict how nutrient content and productivity scale with total plant biomass (phytomass) in whole plant communities. As predicted by our model, net primary productivity as well as whole community nitrogen and phosphorus content all scale allometrically with phytomass across diverse plant communities, from tropical forest to arctic tundra. Importantly, productivity data deviate quantitatively from the theoretically derived prediction, and nutrient productivity (production per unit nutrient) of terrestrial plant communities decreases systematically with increasing total phytomass. These results are consistent with the existence of pronounced competitive size hierarchies. The previously undocumented generality of these 'ecosystem allometries' and their basis in the structure and function of individual plants will likely provide a useful quantitative framework for research linking plant traits to ecosystem processes.
- Kerkhoff, A. J., Fagan, W. F., Elser, J. J., & Enquist, B. J. (2006). Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants. AMERICAN NATURALIST, 168(4), E103-E122.
- Kerkhoff, A. J., Fagan, W. F., Elser, J. J., & Enquist, B. J. (2006). Phylogenetic and growth form variation in the scaling of nitrogen and phosphorus in the seed plants. The American naturalist, 168(4), E103-22.More infoPlant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.
- McGill, B. J., Enquist, B. J., Weiher, E., & Westoby, M. (2006). Rebuilding community ecology from functional traits. Trends in ecology & evolution, 21(4), 178-85.More infoThere is considerable debate about whether community ecology will ever produce general principles. We suggest here that this can be achieved but that community ecology has lost its way by focusing on pairwise species interactions independent of the environment. We assert that community ecology should return to an emphasis on four themes that are tied together by a two-step process: how the fundamental niche is governed by functional traits within the context of abiotic environmental gradients; and how the interaction between traits and fundamental niches maps onto the realized niche in the context of a biotic interaction milieu. We suggest this approach can create a more quantitative and predictive science that can more readily address issues of global change.
- McGill, B. J., Enquist, B. J., Weiher, E., & Westoby, M. (2006). Response to Kearney and Porter: Both functional and community ecologists need to do more for each other. TRENDS IN ECOLOGY & EVOLUTION, 21(9), 482-483.
- McGill, B. J., McGill, B. J., Enquist, B. J., Enquist, B. J., Weiher, E., Weiher, E., Westoby, M., & Westoby, M. (2006). Rebuilding community ecology from functional traits. TRENDS IN ECOLOGY & EVOLUTION, 21(4), 178-185.
- Savage, V. M., Gillooly, J. F., Woodruff, W. H., West, G. B., Allen, A. P., Enquist, B. J., & Brown, J. H. (2004). The predominance of quarter-power scaling in biology. FUNCTIONAL ECOLOGY, 18(2), 257-282.
- Smith, F. A., Brown, J. H., Haskell, J. P., Lyons, S. K., Alroy, J., Charnov, E. L., Dayan, T., Enquist, B. J., Ernest, S. K., Hadly, E. A., Jones, K. E., Kaufman, D. M., Marquet, P. A., Maurer, B. A., Niklas, K. J., Porter, W. P., Tiffney, B., & Willig, M. R. (2004). Similarity of mammalian body size across the taxonomic hierarchy and across space and time. The American naturalist, 163(5), 672-91.More infoAlthough it is commonly assumed that closely related animals are similar in body size, the degree of similarity has not been examined across the taxonomic hierarchy. Moreover, little is known about the variation or consistency of body size patterns across geographic space or evolutionary time. Here, we draw from a data set of terrestrial, nonvolant mammals to quantify and compare patterns across the body size spectrum, the taxonomic hierarchy, continental space, and evolutionary time. We employ a variety of statistical techniques including "sib-sib" regression, phylogenetic autocorrelation, and nested ANOVA. We find an extremely high resemblance (heritability) of size among congeneric species for mammals over approximately 18 g; the result is consistent across the size spectrum. However, there is no significant relationship among the body sizes of congeneric species for mammals under approximately 18 g. We suspect that life-history and ecological parameters are so tightly constrained by allometry at diminutive size that animals can only adapt to novel ecological conditions by modifying body size. The overall distributions of size for each continental fauna and for the most diverse orders are quantitatively similar for North America, South America, and Africa, despite virtually no overlap in species composition. Differences in ordinal composition appear to account for quantitative differences between continents. For most mammalian orders, body size is highly conserved, although there is extensive overlap at all levels of the taxonomic hierarchy. The body size distribution for terrestrial mammals apparently was established early in the Tertiary, and it has remained remarkably constant over the past 50 Ma and across the major continents. Lineages have diversified in size to exploit environmental opportunities but only within limits set by allometric, ecological, and evolutionary constraints.
- Enquist, B. J., Economo, E. P., Huxman, T. E., Allen, A. P., Ignace, D. D., & Gillooly, J. F. (2003). Scaling metabolism from organisms to ecosystems. Nature, 423(6940), 639-42.More infoUnderstanding energy and material fluxes through ecosystems is central to many questions in global change biology and ecology. Ecosystem respiration is a critical component of the carbon cycle and might be important in regulating biosphere response to global climate change. Here we derive a general model of ecosystem respiration based on the kinetics of metabolic reactions and the scaling of resource use by individual organisms. The model predicts that fluxes of CO2 and energy are invariant of ecosystem biomass, but are strongly influenced by temperature, variation in cellular metabolism and rates of supply of limiting resources (water and/or nutrients). Variation in ecosystem respiration within sites, as calculated from a network of CO2 flux towers, provides robust support for the model's predictions. However, data indicate that variation in annual flux between sites is not strongly dependent on average site temperature or latitude. This presents an interesting paradox with regard to the expected temperature dependence. Nevertheless, our model provides a basis for quantitatively understanding energy and material flux between the atmosphere and biosphere.
- West, G. B., Savage, V. M., Gillooly, J., Enquist, B. J., Woodruff, W. H., & Brown, J. H. (2003). Physiology: Why does metabolic rate scale with body size?. Nature, 421(6924), 713; discussion 714.
- Enquist, B. J. (2002). Universal scaling in tree and vascular plant allometry: toward a general quantitative theory linking plant form and function from cells to ecosystems. Tree physiology, 22(15-16), 1045-64.More infoA general theory of allometric scaling that predicts how the proportions of vascular plants and the characteristics of plant communities change or scale with plant size is outlined. The theory rests, in part, on the assumptions of (1) minimal energy dissipation in the transport of fluid through space-filling, fractal-like, branching vascular networks; and (2) the absence of scaling with plant size in the anatomical and physiological attributes of leaves and xylem. The theory shows how the scaling of metabolism with plant size is central to the scaling of whole-plant form and function. It is shown how allometric constraints influence plant populations and, potentially, processes in plant evolution. Rapidly accumulating evidence in support of the general allometric model is reviewed and new evidence is presented. Current work supports the notion that scaling of how plants utilize space and resources is central to the development of a general synthetic and quantitative theory of plant form, function, ecology and diversity.
- Enquist, B. J., & Niklas, K. J. (2002). Global allocation rules for patterns of biomass partitioning in seed plants. SCIENCE, 295(5559), 1517-1520.
- Enquist, B. J., & Niklas, K. J. (2002). Global allocation rules for patterns of biomass partitioning in seed plants. Science (New York, N.Y.), 295(5559), 1517-20.More infoA general allometric model has been derived to predict intraspecific and interspecific scaling relationships among seed plant leaf, stem, and root biomass. Analysis of a large compendium of standing organ biomass sampled across a broad sampling of taxa inhabiting diverse ecological habitats supports the relations predicted by the model and defines the boundary conditions for above- and below-ground biomass partitioning. These canonical biomass relations are insensitive to phyletic affiliation (conifers versus angiosperms) and variation in averaged local environmental conditions. The model thus identifies and defines the limits that have guided the diversification of seed plant biomass allocation strategies.
- Enquist, B. J., Haskell, J. P., & Tiffney, B. H. (2002). General patterns of taxonomic and biomass partitioning in extant and fossil plant communities. Nature, 419(6907), 610-3.More infoA central goal of evolutionary ecology is to identify the general features maintaining the diversity of species assemblages. Understanding the taxonomic and ecological characteristics of ecological communities provides a means to develop and test theories about the processes that regulate species coexistence and diversity. Here, using data from woody plant communities from different biogeographic regions, continents and geologic time periods, we show that the number of higher taxa is a general power-function of species richness that is significantly different from randomized assemblages. In general, we find that local communities are characterized by fewer higher taxa than would be expected by chance. The degree of taxonomic diversity is influenced by modes of dispersal and potential biotic interactions. Further, changes in local diversity are accompanied by regular changes in the partitioning of community biomass between taxa that are also described by a power function. Our results indicate that local and regional processes have consistently regulated community diversity and biomass partitioning for millions of years.
- Niklas, K. J., & Enquist, B. J. (2002). On the vegetative biomass partitioning of seed plant leaves, stems, and roots. The American naturalist, 159(5), 482-97.More infoA central goal of comparative life-history theory is to derive the general rules governing growth, metabolic allocation, and biomass partitioning. Here, we use allometric theory to predict the relationships among annual leaf, stem, and root growth rates (GL, GS, and GR, respectively) across a broad spectrum of seed plant species. Our model predicts isometric scaling relationships among all three organ growth rates: GL is proportional to GS is proportional to GR. It also provides a conceptual basis for understanding the differences in the absolute amounts of biomass allocated to construct the three organ types. Analyses of a large compendium of biomass production rates across diverse seed plant species provide strong statistical support for the predictions of the theory and indicate that reproductive investments may scale isometrically with respect to vegetative organ growth rates. The general rules governing biomass allocation as indexed by the scaling exponents for organ growth rates are remarkably indifferent to plant size and taxonomic affiliation. However, the allometric "constants" for these relationships differ numerically as a function of phenotypic features and local environmental conditions. Nonetheless, at the level of both inter- and intraspecific comparisons, the same proportional biomass allocation pattern holds across extant seed plant species.
- Enquist, B. J., & Niklas, K. J. (2001). Invariant scaling relations across tree-dominated communities. NATURE, 410(6829), 655-660.
- Niklas, K. J., & Enquist, B. J. (2001). Invariant scaling relationships for interspecific plant biomass production rates and body size. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 98(5), 2922-2927.
- West, G. B., Brown, J. H., & Enquist, B. J. (2001). A general model for ontogenetic growth. NATURE, 413(6856), 628-631.
- Enquist, B. J., West, G. B., Charnov, E. L., & Brown, J. H. (1999). Allometric scaling of production and life-history variation in vascular plants. NATURE, 401(6756), 907-911.
- West, G. B., Brown, J. H., & Enquist, B. J. (1999). A general model for the structure and allometry of plant vascular systems. NATURE, 400(6745), 664-667.
- West, G. B., Brown, J. H., & Enquist, B. J. (1999). The fourth dimension of life: Fractal geometry and allometric scaling of organisms. SCIENCE, 284(5420), 1677-1679.
- Enquist, B. J., Brown, J. H., & West, G. B. (1998). Allometric scaling of plant energetics and population density. NATURE, 395(6698), 163-165.
- West, G. B., Brown, J. H., & Enquist, B. J. (1997). A general model for the origin of allometric scaling laws in biology. SCIENCE, 276(5309), 122-126.
- Boyle, B., Meyer, H. W., Enquist, B., Salas, S., Meyer, H., & Smith, D. (2012, 2008). Higher taxa as paleoecological and paleoclimatic indicators: A search for the modern analog of the Florissant fossil flora. In PALEONTOLOGY OF THE UPPER EOCENE FLORISSANT FORMATION, COLORADO, 435, 33-51.
- Michaletz, S., Duran, S., Leavitt, S. W., McDowell, N., Saleska, S. R., Van Haren, J. L., Troch, P. A., Enquist, B. J., Michaletz, S., Duran, S., Leavitt, S. W., McDowell, N., Saleska, S. R., van Haren, J. L., Troch, P. A., & Enquist, B. J. (2019, Aug.). Re-evaluating a stable isotope (δ18O) approach for estimating the temperature of photosynthesis. Ecological Society of America Annual Meeting. Louisville, Kentucky: Ecological Society of America.
- Ernst, K. C., Ernst, K. C., Enquist, B. J., Enquist, B. J., Ferguson, D. B., Ferguson, D. B., Merideth, R., Merideth, R., Park, D. T., Park, D. T., Dang, T., Dang, T., Nuñez-Regueiro, M. M., Nuñez-Regueiro, M. M., Baldwin, E., Baldwin, E., Soto, J. R., Soto, J. R., Breshears, D. D., , Breshears, D. D., et al. (2018, June). Crops in a Changing World: Hidden Forest-Agriculture Teleconnections. 5th European Congress of Conservation Biology. Jyväskylä, Finland: European Congress of Conservation Biology.
- Frank, D. C., Friend, A., Girardin, M., Mahecha, M., Bodesheim, P., Klesse, S., Bjorklund, J., Seftigen, K., Enquist, B. J., Record, S., Charney, N., Evans, M. E., Trouet, V. M., Zhang, Z., Poulter, B., Bouriaud, O., & Babst, F. (2017, April). When tree rings go global: challenges and opportunities for retro- and prospective insights. European Geosciences Union General Assembly. Vienna, Austria: European Geosciences Union.
- Evans, M. E., Merow, C., Record, S., McMahon, S. M., & Enquist, B. J. (2016. Towards Process-based Range Modeling of Many Species(pp 860-871).More infoUnderstanding and forecasting species' geographic distributions in the face of global change is a central priority in biodiversity science. The existing view is that one must choose between correlative models for many species versus process-based models for few species. We suggest that opportunities exist to produce process-based range models for many species, by using hierarchical and inverse modeling to borrow strength across species, fill data gaps, fuse diverse data sets, and model across biological and spatial scales. We review the statistical ecology and population and range modeling literature, illustrating these modeling strategies in action. A variety of large, coordinated ecological datasets that can feed into these modeling solutions already exist, and we highlight organisms that seem ripe for the challenge.
- Enquist, B. J., Tiffney, B. H., & Niklas, K. J. (2014. Metabolic scaling and the evolutionary dynamics of plant size, form, and diversity: Toward a synthesis of ecology, evolution, and paleontology(pp 729-749).
- Goff, S. A., Vaughn, M., McKay, S., Lyons, E., Stapleton, A. E., Gessler, D., Matasci, N., Wang, L., Hanlon, M., Lenards, A., Muir, A., Merchant, N., Lowry, S., Mock, S., Helmke, M., Kubach, A., Narro, M., Hopkins, N., Micklos, D., , Hilgert, U., et al. (2011. The iPlant collaborative: cyberinfrastructure for plant biology.
- Enquist, B. J., Kerkhoff, A. J., Huxman, T. E., & Economo, E. P. (2009. Adaptive differences in plant physiology and ecosystem paradoxes: insights from metabolic scaling theory(pp 591-609).
- Violle, C., Enquist, B. J., McGill, B. J., Jiang, L., Albert, C. H., Hulshof, C., Jung, V., & Messier, J. (2007. The return of the variance: intraspecific variability in community ecology(pp 244-252).
- Kerkhoff, A. J., & Enquist, B. J. (2012, APR 7). Multiplicative by nature: Why logarithmic transformation is necessary in allometry. JOURNAL OF THEORETICAL BIOLOGY.
- Enquist, B. J., Allen, A. P., Brown, J. H., Gillooly, J. F., Kerkhoff, A. J., Niklas, K. J., Price, C. A., & West, G. B. (2011, FEB 1). Does the exception prove the rule?. NATURE.