Laura Meredith

Interests

Teaching

BiogeochemistryEcosystem GenomicsBiosphere-Atmosphere InteractionsAtmospheric ChemistryEnvironmental Microbiology

Research

Microorganisms have produced dramatic shifts in the composition of the Earth’s atmosphere, and they continue to drive significant exchange of trace gases and aerosols between the land, oceans, and atmosphere. Many microbe-mediated processes have a leading-order impact on climate variability, are themselves susceptible to climate change (potential for feedbacks), and are poorly understood (e.g., CH4, N2O, biological particles). In terrestrial ecosystems, soil microorganisms provide benefits to society (ecosystem services such as nutrient cycling), which depend strongly on land use (urban, rural, agricultural, natural) and land surface type. The Meredith lab focuses on improving the process-based understanding of the environmental and biological drivers of microbe-mediated trace gas fluxes using an interdisciplinary set of laboratory and observational methods.Linking gene to function for microbe-mediated gas fluxesDetermining key controls on ecosystem trace gas fluxes

Courses

Scholarly Contributions

Chapters

• Troch, P. A., Troch, P. A., Troch, P. A., Zeng, X., Zeng, X., Zeng, X., Van Haren, J. L., Van Haren, J. L., Van Haren, J. L., Tuller, M., Tuller, M., Tuller, M., Sibayan, M., Sibayan, M., Sibayan, M., Schaap, M. G., Schaap, M. G., Schaap, M. G., Saleska, S. R., , Saleska, S. R., et al. (2018). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments. Rijeka, Croatia: IN TECH d.o.o.
• Troch, P. A., Zeng, X., Van Haren, J. L., Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pohlmann, M. A., Pelletier, J. D., Monson, R. K., Maier, R. M., Kim, M., Huxman, T. E., Ferre, P. A., Durcik, M., DeLong, S. B., Cueva, A., , Chorover, J. D., et al. (2018). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments. Rijeka, Croatia: IN TECH d.o.o. doi:10.5772/intechopen.72325
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  Volkmann, T.H.M., co-authors, X. Zeng, ad P.A. Troch, 2018: Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Change. Chapter 2 in the book "Hydrology of Artificial and Controlled Experiments", doi: 10.5772/intechopen.72325.
• Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pohlmann, M. A., Pelletier, J. D., Monson, R. K., Maier, R. M., Kim, M., Huxman, T. E., Ferre, P. A., Durcik, M., DeLong, S. B., Cueva, A., Chorover, J. D., Bugaj, A., Breshears, D. D., , Adams, J. R., et al. (2018). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments(pp 25-74). Rijeka, Croatia: IntechOpen Limited.
• Volkmann, T. H., Sengupta, A., Pangle, L. A., Dontsova, K. M., Barron-Gafford, G. A., Harman, C. J., Niu, G., Meredith, L., Abramson, N., Alves Meira Neto, A., Wang, Y., Adams, J. R., Breshears, D. D., Bugaj, A., Chorover, J. D., Cueva, A., DeLong, S. B., Durcik, M., Ferre, P. A., , Huxman, T. E., et al. (2018). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments, Jiu-Fu Liu and Wei-Zu Gu. Rijeka, Croatia: IntechOpen. doi:10.5772/intechopen.72325
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  Understanding the process interactions and feedbacks among water, porous geological media, microbes, and vascular plants is crucial for improving predictions of the response of Earth’s critical zone to future climatic conditions. However, the integrated coevolution of landscapes under change is notoriously difficult to investigate. Laboratory studies are limited in spatial and temporal scale, while field studies lack observational density and control. To bridge the gap between controlled laboratory and uncontrollable field studies, the University of Arizona built a macrocosm experiment of unprecedented scale: the Landscape Evolution Observatory (LEO). LEO comprises three replicated, heavily instrumented, hillslope-scale model landscapes within the environmentally controlled Biosphere 2 facility. The model landscapes were designed to initially be simple and purely abiotic, enabling scientists to observe each step in the landscapes’ evolution as they undergo physical, chemical, and biological changes over many years. This chapter describes the model systems and associated research facilities and illustrates how LEO allows for tracking of multiscale matter and energy fluxes at a level of detail impossible in field experiments. Initial sensor, sampler, and soil coring data are already providing insights into the tight linkages between water flow, weathering, and microbial community development. These interacting processes are anticipated to drive the model systems to increasingly complex states and will be impacted by the introduction of vascular plants and changes in climatic regimes over the years to come. By intensively monitoring the evolutionary trajectory, integrating data with mathematical models, and fostering community-wide collaborations, we envision that emergent landscape structures and functions can be linked, and significant progress can be made toward predicting the coupled hydro-biogeochemical and ecological responses to global change.
• Troch, P. A., Zeng, X., Van Haren, J. L., Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pohlmann, M. A., Pelletier, J. D., Monson, R. K., Maier, R. M., Kim, M., Huxman, T. E., Ferre, P. A., Durcik, M., DeLong, S. B., Cueva, A., , Chorover, J. D., et al. (2017). Controlled Experiments of Hillslope Coevolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological Changes. In Hydrology of Artificial and Controlled Experiments. Rijeka, Croatia: IN TECH d.o.o.

Journals/Publications

• Crocker, L., Guo, J., U’Ren, J. M., Pugliese, G., Ladd, S. N., Werner, C., & Meredith, L. K. (2025).

  Volatile Organic Compound (VOC) Exchange in Tropical Leaf Litter in Response to Wetting: An Automated Scheme to Classify Flux Pulse Dynamics

  . Journal of Geophysical Research: Biogeosciences, 130(Issue 10). doi:10.1029/2025jg008774
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  Leaf litter emits volatile organic compounds (VOCs) that can impact atmospheric and soil processes, particularly in ecosystems with episodic litterfall and decomposition such as dry-wet transitions in tropical forests. Litter VOCs may originate from both plant and microbial sources that are challenging to disentangle but may be reflected in the temporal patterns of litter VOC fluxes to wetting. Here, we collected Clitoria fairchildiana litter after an ecosystem-scale experimental drought in the Biosphere 2 Tropical Rainforest and measured litter VOC fluxes over a 10-day incubation to: (a) identify and quantify litter VOC fluxes; (b) examine the impacts of moisture; and (c) distinguish plant from microbial VOCs. In total, we observed 121 masses exhibiting either significant emission (88%) or uptake (12%) fluxes. Emissions of methanol, acetaldehyde, and acetone were the dominant fluxes. Wetting dry litter altered the flux of 47% of VOCs: 66 decreased to pre-wetting levels within 24 hr although 25 sustained higher emission rates. We categorized VOCs during wetting as plant derived (55%), microbial-derived production (21%), microbial uptake (12%), and unknown (13%) by visual inspection of the flux time series. Automated classification of the wetting pulses with fitted model parameters was consistent with the visual categorization approximately 80% of the time. Our results provide measurements of litter VOC fluxes for a widespread tropical plant. Moreover, we illustrate an automated data-model approach to efficiently characterize and categorize trace gas pulses for litter VOC fluxes that is translatable to other types of trace gases, forcings, and ecosystem components including soil.
• Ledford, S. M., Geffre, P., Marschmann, G. L., Karaoz, U., Brodie, E. L., & Meredith, L. K. (2025).

  Volatile traits expand the microbial playbook

  . Trends in Microbiology.
• Byron, J., Kreuzwieser, J., Purser, G., Haren, J., Ladd, S. N., Meredith, L., Werner, C., & Williams, J. (2021). Chiral monoterpenes reveal forest emission mechanisms and drought responses. Nature.
• Gil-Loaiza, J., Roscioli, J. R., Shorter, J. H., Volkmann, T. H., Ng, W., Krechmer, J. E., & Meredith, L. K. (2021). Versatile soil gas concentration and isotope monitoring: optimization and integration of novel soil gas probes with online trace gas detection. Biogeosciences, 19(1), 165--185.
• Huang, J., Ladd, S. N., Ingrisch, J., Kübert, A., Meredith, L. K., van Haren, J., Bamberger, I., Daber, L. E., Kühnhammer, K., Bailey, K., Hu, J., Fudyma, J., Shi, L., Dippold, M. A., Meeran, K., Miller, L., O’Brien, M. J., Yang, H., Herrera-Ramírez, D., , Hartmann, H., et al. (2024). The mobilization and transport of newly fixed carbon are driven by plant water use in an experimental rainforest under drought. Journal of Experimental Botany, 75(8), 2545-2557. doi:10.1093/jxb/erae030
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  Non-structural carbohydrates (NSCs) are building blocks for biomass and fuel metabolic processes. However, it remains unclear how tropical forests mobilize, export, and transport NSCs to cope with extreme droughts. We combined drought manipulation and ecosystem 13CO2 pulse-labeling in an enclosed rainforest at Biosphere 2, assessed changes in NSCs, and traced newly assimilated carbohydrates in plant species with diverse hydraulic traits and canopy positions. We show that drought caused a depletion of leaf starch reserves and slowed export and transport of newly assimilated carbohydrates below ground. Drought effects were more pronounced in conservative canopy trees with limited supply of new photosynthates and relatively constant water status than in those with continual photosynthetic supply and deteriorated water status. We provide experimental evidence that local utilization, export, and transport of newly assimilated carbon are closely coupled with plant water use in canopy trees. We highlight that these processes are critical for understanding and predicting tree resistance and ecosystem fluxes in tropical forest under drought.
• Ledford, S., & Meredith, L. (2024). Volatile Organic Compound Metabolism on Early Earth. Journal of Molecular Evolution, 92(5). doi:10.1007/s00239-024-10184-x
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  Biogenic volatile organic compounds (VOCs) constitute a significant portion of gas-phase metabolites in modern ecosystems and have unique roles in moderating atmospheric oxidative capacity, solar radiation balance, and aerosol formation. It has been theorized that VOCs may account for observed geological and evolutionary phenomena during the Archaean, but the direct contribution of biology to early non-methane VOC cycling remains unexplored. Here, we provide an assessment of all potential VOCs metabolized by the last universal common ancestor (LUCA). We identify enzyme functions linked to LUCA orthologous protein groups across eight literature sources and estimate the volatility of all associated substrates to identify ancient volatile metabolites. We hone in on volatile metabolites with confirmed modern emissions that exist in conserved metabolic pathways and produce a curated list of the most likely LUCA VOCs. We introduce volatile organic metabolites associated with early life and discuss their potential influence on early carbon cycling and atmospheric chemistry.
• Meredith, L. K., & Tfaily, M. M. (2021). Capturing the microbial volatilome: an oft overlooked'ome'. Trends in microbiology.
• Hildebrand, G. A., Honeker, L. K., Freire-Zapata, V., Ayala-Ortiz, C., Rajakaruna, S., Fudyma, J., Daber, L. E., AminiTabrizi, R., Chu, R. L., Toyoda, J., Flowers, S. E., Hoyt, D. W., Hamdan, R., Gil-Loaiza, J., Shi, L., Dippold, M. A., Ladd, S. N., Werner, C., Meredith, L. K., & Tfaily, M. M. (2023). Uncovering the dominant role of root metabolism in shaping rhizosphere metabolome under drought in tropical rainforest plants. Science of the Total Environment, 899. doi:10.1016/j.scitotenv.2023.165689
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  Plant-soil-microbe interactions are crucial for driving rhizosphere processes that contribute to metabolite turnover and nutrient cycling. With the increasing frequency and severity of water scarcity due to climate warming, understanding how plant-mediated processes, such as root exudation, influence soil organic matter turnover in the rhizosphere is essential. In this study, we used 16S rRNA gene amplicon sequencing, rhizosphere metabolomics, and position-specific 13C-pyruvate labeling to examine the effects of three different plant species (Piper auritum, Hibiscus rosa sinensis, and Clitoria fairchildiana) and their associated microbial communities on soil organic carbon turnover in the rhizosphere. Our findings indicate that in these tropical plants, the rhizosphere metabolome is primarily shaped by the response of roots to drought rather than direct shifts in the rhizosphere bacterial community composition. Specifically, the reduced exudation of plant roots had a notable effect on the metabolome of the rhizosphere of P. auritum, with less reliance on neighboring microbes. Contrary to P. auritum, H. rosa sinensis and C. fairchildiana experienced changes in their exudate composition during drought, causing alterations to the bacterial communities in the rhizosphere. This, in turn, had a collective impact on the rhizosphere's metabolome. Furthermore, the exclusion of phylogenetically distant microbes from the rhizosphere led to shifts in its metabolome. Additionally, C. fairchildiana appeared to be associated with only a subset of symbiotic bacteria under drought conditions. These results indicate that plant species-specific microbial interactions systematically change with the root metabolome. As roots respond to drought, their associated microbial communities adapt, potentially reinforcing the drought tolerance strategies of plant roots. These findings have significant implications for maintaining plant health and preference during drought stress and improving plant performance under climate change.
• Kübert, A., Dubbert, M., Bamberger, I., Kühnhammer, K., Beyer, M., van Haren, J., Bailey, K., Hu, J., Meredith, L. K., Nemiah Ladd, S., & Werner, C. (2023). Tracing plant source water dynamics during drought by continuous transpiration measurements: An in-situ stable isotope approach. Plant Cell and Environment, 46(Issue 1). doi:10.1111/pce.14475
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  The isotopic composition of xylem water (δX) is of considerable interest for plant source water studies. In-situ monitored isotopic composition of transpired water (δT) could provide a nondestructive proxy for δX-values. Using flow-through leaf chambers, we monitored 2-hourly δT-dynamics in two tropical plant species, one canopy-forming tree and one understory herbaceous species. In an enclosed rainforest (Biosphere 2), we observed δT-dynamics in response to an experimental severe drought, followed by a 2H deep-water pulse applied belowground before starting regular rain. We also sampled branches to obtain δX-values from cryogenic vacuum extraction (CVE). Daily flux-weighted δ18OT-values were a good proxy for δ18OX-values under well-watered and drought conditions that matched the rainforest's water source. Transpiration-derived δ18OX-values were mostly lower than CVE-derived values. Transpiration-derived δ2HX-values were relatively high compared to source water and consistently higher than CVE-derived values during drought. Tracing the 2H deep-water pulse in real-time showed distinct water uptake and transport responses: a fast and strong contribution of deep water to canopy tree transpiration contrasting with a slow and limited contribution to understory species transpiration. Thus, the in-situ transpiration method is a promising tool to capture rapid dynamics in plant water uptake and use by both woody and nonwoody species.
• Ladd, S., Daber, L., Bamberger, I., Kreuzwieser, J., Purser, G., Ingrisch, J., Deleeuw, J., van Haren, J., Meredith, L., Werner, C., & Kübert, A. (2023). Leaf-level metabolic changes in response to drought affect daytime CO2 emission and isoprenoid synthesis pathways. Tree Physiology, 43(11). doi:10.1093/treephys/tpad094
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  In the near future, climate change will cause enhanced frequency and/or severity of droughts in terrestrial ecosystems, including tropical forests. Drought responses by tropical trees may affect their carbon use, including production of volatile organic compounds (VOCs), with implications for carbon cycling and atmospheric chemistry that are challenging to predict. It remains unclear how metabolic adjustments by mature tropical trees in response to drought will affect their carbon fluxes associated with daytime CO2 production and VOC emission. To address this gap, we used position-specific 13C-pyruvate labeling to investigate leaf CO2 and VOC fluxes from four tropical species before and during a controlled drought in the enclosed rainforest of Biosphere 2 (B2). Overall, plants that were more drought-sensitive had greater reductions in daytime CO2 production. Although daytime CO2 production was always dominated by non-mitochondrial processes, the relative contribution of CO2 from the tricarboxylic acid cycle tended to increase under drought. A notable exception was the legume tree Clitoria fairchildiana R.A. Howard, which had less anabolic CO2 production than the other species even under pre-drought conditions, perhaps due to more efficient refixation of CO2 and anaplerotic use for amino acid synthesis. The C. fairchildiana was also the only species to allocate detectable amounts of 13C label to VOCs and was a major source of VOCs in B2. In C. fairchildiana leaves, our data indicate that intermediates from the mevalonic acid (MVA) pathway are used to produce the volatile monoterpene trans-β-ocimene, but not isoprene. This apparent crosstalk between the MVA and methylerythritol phosphate pathways for monoterpene synthesis declined with drought. Finally, although trans-β-ocimene emissions increased under drought, it was increasingly sourced from stored intermediates and not de novo synthesis. Unique metabolic responses of legumes may play a disproportionate role in the overall changes in daytime CO2 and VOC fluxes in tropical forests experiencing drought.
• Pavlopoulos, G. A., Baltoumas, F. A., Liu, S., Selvitopi, O., Camargo, A. P., Nayfach, S., Azad, A., Roux, S., Call, L., Ivanova, N. N., Chen, I. M., Paez-Espino, D., Karatzas, E., Acinas, S. G., Ahlgren, N., Attwood, G., Baldrian, P., Berry, T., Bhatnagar, J. M., , Bhaya, D., et al. (2023). Unraveling the functional dark matter through global metagenomics. Nature, 622(Issue 7983). doi:10.1038/s41586-023-06583-7
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  Metagenomes encode an enormous diversity of proteins, reflecting a multiplicity of functions and activities1,2. Exploration of this vast sequence space has been limited to a comparative analysis against reference microbial genomes and protein families derived from those genomes. Here, to examine the scale of yet untapped functional diversity beyond what is currently possible through the lens of reference genomes, we develop a computational approach to generate reference-free protein families from the sequence space in metagenomes. We analyse 26,931 metagenomes and identify 1.17 billion protein sequences longer than 35 amino acids with no similarity to any sequences from 102,491 reference genomes or the Pfam database3. Using massively parallel graph-based clustering, we group these proteins into 106,198 novel sequence clusters with more than 100 members, doubling the number of protein families obtained from the reference genomes clustered using the same approach. We annotate these families on the basis of their taxonomic, habitat, geographical and gene neighbourhood distributions and, where sufficient sequence diversity is available, predict protein three-dimensional models, revealing novel structures. Overall, our results uncover an enormously diverse functional space, highlighting the importance of further exploring the microbial functional dark matter.
• Buzzard, V., Cueva, A., Gil-loaiza, J., Meredith, L. K., & Thorne, D. (2022). Sensitivity of soil hydrogen uptake to natural and managed moisture dynamics in a semiarid urban ecosystem.. PeerJ, 10(Issue), e12966. doi:10.7717/peerj.12966
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  The North American Monsoon season (June-September) in the Sonoran Desert brings thunderstorms and heavy rainfall. These rains bring cooler temperature and account for roughly half of the annual precipitation making them important for biogeochemical processes. The intensity of the monsoon rains also increase flooding in urban areas and rely on green infrastructure (GI) stormwater management techniques such as water harvesting and urban rain gardens to capture runoff. The combination of increased water availability during the monsoon and water management provide a broad moisture regime for testing responses in microbial metabolism to natural and managed soil moisture pulses in drylands. Soil microbes rely on atmospheric hydrogen (H2) as an important energy source in arid and semiarid landscapes with low soil moisture and carbon availability. Unlike mesic ecosystems, transient water availability in arid and semiarid ecosystems has been identified as a key limiting driver of microbe-mediated H2 uptake. We measured soil H2 uptake in rain gardens exposed to three commonly used water harvesting practices during the monsoon season in Tucson AZ, USA. In situ static chamber measurements were used to calculate H2 uptake in each of the three water harvesting treatments passive (stormwater runoff), active (stored rooftop runoff), and greywater (used laundry water) compared to an unaltered control treatment to assess the effects of water management practices on soil microbial activity. In addition, soils were collected from each treatment and brought to the lab for an incubation experiment manipulating the soil moisture to three levels capturing the range observed from field samples. H2 fluxes from all treatments ranged between -0.72 nmol m-2 s-1 and -3.98 nmol m-2 s-1 over the monsoon season. Soil H2 uptake in the greywater treatment was on average 53% greater than the other treatments during pre-monsoon, suggesting that the increased frequency and availability of water in the greywater treatment resulted in higher H2 uptake during the dry season. H2 uptake was significantly correlated with soil moisture (r = -0.393, p = 0.001, df = 62) and temperature (r = 0.345, p = 0.005, df = 62). Our findings suggest that GI managed residential soils can maintain low levels of H2 uptake during dry periods, unlike unmanaged systems. The more continuous H2 uptake associated with GI may help reduce the impacts of drought on H2 cycling in semiarid urban ecosystems.
• Fremin, B., Bhatt, A., Kyrpides, N., Sengupta, A., Sczyrba, A., Maria da Silva, A., Buchan, A., Gaudin, A., Brune, A., Hirsch, A., Neumann, A., Shade, A., Visel, A., Campbell, B., Baker, B., Hedlund, B., Crump, B., Currie, C., Kelly, C., , Craft, C., et al. (2022). Thousands of small, novel genes predicted in global phage genomes. Cell Reports, 39(12). doi:10.1016/j.celrep.2022.110984
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  Small genes (40,000 small-gene families in ∼2.3 million phage genome contigs. We find that small genes in phage genomes are approximately 3-fold more prevalent than in host prokaryotic genomes. Our approach enriches for small genes that are translated in microbiomes, suggesting the small genes identified are coding. More than 9,000 families encode potentially secreted or transmembrane proteins, more than 5,000 families encode predicted anti-CRISPR proteins, and more than 500 families encode predicted antimicrobial proteins. By combining homology and genomic-neighborhood analyses, we reveal substantial novelty and diversity within phage biology, including small phage genes found in multiple host phyla, small genes encoding proteins that play essential roles in host infection, and small genes that share genomic neighborhoods and whose encoded proteins may share related functions.
• Gil-loaiza, J., Krechmer, J. E., Meredith, L. K., Ng, W., Roscioli, J. R., Shorter, J. H., & Volkmann, T. H. (2022). Versatile soil gas concentration and isotope monitoring: optimization and integration of novel soil gas probes with online trace gas detection. Biogeosciences, 19(1), 165-185. doi:10.5194/bg-19-165-2022
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  Abstract. Gas concentrations and isotopic signatures can unveil microbial metabolisms and their responses to environmental changes in soil. Currently, few methods measure in situ soil trace gases such as the products of nitrogen and carbon cycling or volatile organic compounds (VOCs) that constrain microbial biochemical processes like nitrification, methanogenesis, respiration, and microbial communication. Versatile trace gas sampling systems that integrate soil probes with sensitive trace gas analyzers could fill this gap with in situ soil gas measurements that resolve spatial (centimeters) and temporal (minutes) patterns. We developed a system that integrates new porous and hydrophobic sintered polytetrafluoroethylene (sPTFE) diffusive soil gas probes that non-disruptively collect soil gas samples with a transfer system to direct gas from multiple probes to one or more central gas analyzer(s) such as laser and mass spectrometers. Here, we demonstrate the feasibility and versatility of this automated multiprobe system for soil gas measurements of isotopic ratios of nitrous oxide (δ18O, δ15N, and the 15N site preference of N2O), methane, carbon dioxide (δ13C), and VOCs. First, we used an inert silica matrix to challenge probe measurements under controlled gas conditions. By changing and controlling system flow parameters, including the probe flow rate, we optimized recovery of representative soil gas samples while reducing sampling artifacts on subsurface concentrations. Second, we used this system to provide a real-time window into the impact of environmental manipulation of irrigation and soil redox conditions on in situ N2O and VOC concentrations. Moreover, to reveal the dynamics in the stable isotope ratios of N2O (i.e., 14N14N16O, 14N15N16O, 15N14N16O, and 14N14N18O), we developed a new high-precision laser spectrometer with a reduced sample volume demand. Our integrated system – a tunable infrared laser direct absorption spectrometry (TILDAS) in parallel with Vocus proton transfer reaction mass spectrometry (PTR-MS), in line with sPTFE soil gas probes – successfully quantified isotopic signatures for N2O, CO2, and VOCs in real time as responses to changes in the dry–wetting cycle and redox conditions. Broadening the collection of trace gases that can be monitored in the subsurface is critical for monitoring biogeochemical cycles, ecosystem health, and management practices at scales relevant to the soil system.
• Honeker, L. K., Hildebrand, G. A., Fudyma, J. D., Daber, L. E., Hoyt, D., Flowers, S. E., Gil-Loaiza, J., Kübert, A., Bamberger, I., Anderton, C. R., & others, . (2022). Elucidating Drought-Tolerance Mechanisms in Plant Roots through 1H NMR Metabolomics in Parallel with MALDI-MS, and NanoSIMS Imaging Techniques. Environmental Science \& Technology.
• , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., , ., Nayfach, S., Roux, S., Seshadri, R., Udwary, D., Varghese, N., Schulz, F., , Wu, D., et al. (2021). Publisher Correction: A genomic catalog of Earth’s microbiomes (Nature Biotechnology, (2021), 39, 4, (499-509), 10.1038/s41587-020-0718-6). Nature Biotechnology, 39(4). doi:10.1038/s41587-020-00769-4
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  This paper was originally published under standard Springer Nature copyright (© The Author(s), under exclusive licence to Springer Nature America, Inc.). It is now available as an open-access paper under a Creative Commons Attribution 4.0 International license. The error has been corrected in the print, HTML and PDF versions of the article.
• Buzzard, V., Gil-Loaiza, J., Grachet, N. G., Talkington, H., Youngerman, C., Tfaily, M. M., & Meredith, L. K. (2021). Green infrastructure influences soil health: Biological divergence one year after installation. Science of The Total Environment, 801, 149644.
• Kooijmans, L. M., Cho, A., Ma, J., Kaushik, A., Haynes, K. D., Baker, I., Luijkx, I. T., Groenink, M., Peters, W., Miller, J. B., & Meredith, L. (2021). Evaluation of carbonyl sulfide biosphere exchange in the Simple Biosphere Model (SiB4). Biogeosciences, 18(24), 6547--6565.
• Roscioli, J. R., Meredith, L. K., Shorter, J. H., Gil-Loaiza, J., & Volkmann, T. H. (2021). Soil gas probes for monitoring trace gas messengers of microbial activity. Scientific reports, 11(1), 1--11.
• Sengupta, A., Volkmann, T. H., Danczak, R. E., Stegen, J. C., Dontsova, K. M., Abramson, N., Bugaj, A. S., Volk, M. J., Matos, K. A., Meira-Neto, A. A., Barberan, A., Neilson, J. W., Maier, R. M., Chorover, J. D., Troch, P. A., & Meredith, L. (2021). Contrasting Community Assembly Forces Drive Microbial Structural and Potential Functional Responses to Precipitation in an Incipient Soil System.. Frontiers in Microbiology, 12(3414).
• Tfaily, M. M., Meredith, L., Krechmer, J. E., Honeker, L. K., & Graves, K. R. (2021). The Volatilome: A Vital Piece of the Complete Soil Metabolome. Frontiers in Environmental Science, 9. doi:10.3389/fenvs.2021.649905
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  Soils harbor complex biological processes intertwined with metabolic inputs from microbes and plants. Measuring the soil metabolome can reveal active metabolic pathways, providing insight into the presence of specific organisms and ecological interactions. A subset of the metabolome is volatile; however, current soil studies rarely consider volatile organic compounds (VOCs), contributing to biases in sample processing and metabolic analytical methods. Therefore, we hypothesize that the volatility of detected compounds measured using current metabolic analytical methods will be lower than undetected compounds, a reflection of missed VOCs. To illustrate this, we examined a peatland metabolomic dataset collected using three common analysis techniques: nuclear magnetic resonance (NMR), gas chromatography-mass spectroscopy (GC-MS), and fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). We mapped the compounds to three metabolic pathways (monoterpenoid biosynthesis, diterpenoid biosynthesis, and polycyclic aromatic hydrocarbon degradation), chosen for their activity in peatland ecosystems and involvement of VOCs. We estimated the volatility of the compounds by calculating relative volatility indices (RVIs), and as hypothesized, the average RVI of undetected compounds within each of our focal pathways was higher than detected compounds (p < 0.001). Our findings suggest that typical soil metabolomic analytical methods may overlook VOCs and leave missing links in metabolic pathways. To more completely represent the volatile fraction of the soil metabolome, we suggest that environmental scientists take into consideration these biases when designing and interpreting their data and/or add direct online measurement methods that capture the integral role of VOCs in soil systems.
• Werner, C., Meredith, L. K., Ladd, S. N., Ingrisch, J., K\"ubert, A., Haren, J., Bahn, M., Bamberger, I., Beyer, M., Blomdahl, D., & others, . (2021). Ecosystem fluxes during drought and recovery in an experimental forest. Science, 374(6574), 1514--1518.
• Gil-Loaiza, J., Roscioli, J. R., Shorter, J. H., Volkmann, T. H., Ng, W., Krechmer, J. E., & Meredith, L. K. (2020). Versatile soil gas concentration and isotope monitoring: optimization and integration of novel soil gas probes with online trace gas detection. Biogeosciences Discussions, 1--38.
• Jordaan, K., Lappan, R., Dong, X., Aitkenhead, I. J., Bay, S. K., Chiri, E., Wieler, N., Meredith, L. K., Cowan, D. A., Chown, S. L., & Greening, C. (2020). Hydrogen-Oxidizing Bacteria Are Abundant in Desert Soils and Strongly Stimulated by Hydration. mSystems, 5(6).
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  How the diverse bacterial communities inhabiting desert soils maintain energy and carbon needs is much debated. Traditionally, most bacteria are thought to persist by using organic carbon synthesized by photoautotrophs following transient hydration events. Recent studies focused on Antarctic desert soils have revealed, however, that some bacteria use atmospheric trace gases, such as hydrogen (H), to conserve energy and fix carbon independently of photosynthesis. In this study, we investigated whether atmospheric H oxidation occurs in four nonpolar desert soils and compared this process to photosynthesis. To do so, we first profiled the distribution, expression, and activities of hydrogenases and photosystems in surface soils collected from the South Australian desert over a simulated hydration-desiccation cycle. Hydrogenase-encoding sequences were abundant in the metagenomes and metatranscriptomes and were detected in actinobacterial, acidobacterial, and cyanobacterial metagenome-assembled genomes. Native dry soil samples mediated H oxidation, but rates increased 950-fold following wetting. Oxygenic and anoxygenic phototrophs were also detected in the community but at lower abundances. Hydration significantly stimulated rates of photosynthetic carbon fixation and, to a lesser extent, dark carbon assimilation. Hydrogenase genes were also widespread in samples from three other climatically distinct deserts, the Namib, Gobi, and Mojave, and atmospheric H oxidation was also greatly stimulated by hydration at these sites. Together, these findings highlight that H is an important, hitherto-overlooked energy source supporting bacterial communities in desert soils. Contrary to our previous hypotheses, however, H oxidation occurs simultaneously rather than alternately with photosynthesis in such ecosystems and may even be mediated by some photoautotrophs. Desert ecosystems, spanning a third of the earth's surface, harbor remarkably diverse microbial life despite having a low potential for photosynthesis. In this work, we reveal that atmospheric hydrogen serves as a major previously overlooked energy source for a large proportion of desert bacteria. We show that both chemoheterotrophic and photoautotrophic bacteria have the potential to oxidize hydrogen across deserts sampled across four continents. Whereas hydrogen oxidation was slow in native dry deserts, it increased by three orders of magnitude together with photosynthesis following hydration. This study revealed that continual harvesting of atmospheric energy sources may be a major way that desert communities adapt to long periods of water and energy deprivation, with significant ecological and biogeochemical ramifications.
• Kroeger, M. E., Meredith, L. K., Meyer, K. M., Webster, K. D., De, C., De, S., Tsai, S. M., Van, H. J., Saleska, S., Bohannan, B. J., & others, . (2020). Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon. The ISME Journal, 1--15.
• Kroeger, M. E., Meredith, L. K., Meyer, K. M., Webster, K. D., de Camargo, P. B., de Souza, L. F., Tsai, S. M., van Haren, J., Saleska, S., Bohannan, B. J., Rodrigues, J. L., Berenguer, E., Barlow, J., & Nüsslein, K. (2020). Rainforest-to-pasture conversion stimulates soil methanogenesis across the Brazilian Amazon. The ISME journal.
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  The Amazon rainforest is a biodiversity hotspot and large terrestrial carbon sink threatened by agricultural conversion. Rainforest-to-pasture conversion stimulates the release of methane, a potent greenhouse gas. The biotic methane cycle is driven by microorganisms; therefore, this study focused on active methane-cycling microorganisms and their functions across land-use types. We collected intact soil cores from three land use types (primary rainforest, pasture, and secondary rainforest) of two geographically distinct areas of the Brazilian Amazon (Santarém, Pará and Ariquemes, Rondônia) and performed DNA stable-isotope probing coupled with metagenomics to identify the active methanotrophs and methanogens. At both locations, we observed a significant change in the composition of the isotope-labeled methane-cycling microbial community across land use types, specifically an increase in the abundance and diversity of active methanogens in pastures. We conclude that a significant increase in the abundance and activity of methanogens in pasture soils could drive increased soil methane emissions. Furthermore, we found that secondary rainforests had decreased methanogenic activity similar to primary rainforests, and thus a potential to recover as methane sinks, making it conceivable for forest restoration to offset greenhouse gas emissions in the tropics. These findings are critical for informing land management practices and global tropical rainforest conservation.
• Martinez-Sosa, P., Tierney, J. E., & Meredith, L. K. (2020). Controlled lacustrine microcosms show a brGDGT response to environmental perturbations. Organic Geochemistry, 145, 104041.
• Meredith, L. K., Boye, K., Savage, K., & Vargas, R. (2020). Formation and fluxes of soil trace gases.
• Meyer, K. M., Morris, A. H., Webster, K., Klein, A. M., Kroeger, M. E., Meredith, L. K., Brændholt, A., Nakamura, F., Venturini, A., Fonseca de Souza, L., Shek, K. L., Danielson, R., van Haren, J., Barbosa de Camargo, P., Tsai, S. M., Dini-Andreote, F., de Mauro, J. M., Barlow, J., Berenguer, E., , Nüsslein, K., et al. (2020). Belowground changes to community structure alter methane-cycling dynamics in Amazonia. Environment International, 145. doi:10.1016/j.envint.2020.106131
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  Amazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with increases in soil methane (CH4) emission. To better understand the drivers of this change, we measured soil CH4 flux, environmental conditions, and belowground microbial community structure across primary forests, cattle pastures, and secondary forests in two Amazonian regions. We show that pasture soils emit high levels of CH4 (mean: 3454.6 ± 9482.3 μg CH4 m−2 d−1), consistent with previous reports, while forest soils on average emit CH4 at modest rates (mean: 9.8 ± 120.5 μg CH4 m−2 d−1), but often act as CH4 sinks. We report that secondary forest soils tend to consume CH4 (mean: −10.2 ± 35.7 μg CH4 m−2 d−1), demonstrating that pasture CH4 emissions can be reversed. We apply a novel computational approach to identify microbial community attributes associated with flux independent of soil chemistry. While this revealed taxa known to produce or consume CH4 directly (i.e. methanogens and methanotrophs, respectively), the vast majority of identified taxa are not known to cycle CH4. Each land use type had a unique subset of taxa associated with CH4 flux, suggesting that land use change alters CH4 cycling through shifts in microbial community composition. Taken together, we show that microbial composition is crucial for understanding the observed CH4 dynamics and that microorganisms provide explanatory power that cannot be captured by environmental variables.
• Meyer, K. M., Morris, A. H., Webster, K., Klein, A. M., Kroeger, M. E., Meredith, L. K., Brændholt, A., Nakamura, F., Venturini, A., Fonseca de Souza, L., Shek, K. L., Danielson, R., van Haren, J., Barbosa de Camargo, P., Tsai, S. M., Dini-Andreote, F., de Mauro, J. M., Barlow, J., Berenguer, E., , Nüsslein, K., et al. (2020). Belowground changes to community structure alter methane-cycling dynamics in Amazonia. Environment international, 145, 106131.
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  Amazonian rainforest is undergoing increasing rates of deforestation, driven primarily by cattle pasture expansion. Forest-to-pasture conversion has been associated with increases in soil methane (CH) emission. To better understand the drivers of this change, we measured soil CH flux, environmental conditions, and belowground microbial community structure across primary forests, cattle pastures, and secondary forests in two Amazonian regions. We show that pasture soils emit high levels of CH (mean: 3454.6 ± 9482.3 μg CH m d), consistent with previous reports, while forest soils on average emit CH at modest rates (mean: 9.8 ± 120.5 μg CH m d), but often act as CH sinks. We report that secondary forest soils tend to consume CH (mean: -10.2 ± 35.7 μg CH m d), demonstrating that pasture CH emissions can be reversed. We apply a novel computational approach to identify microbial community attributes associated with flux independent of soil chemistry. While this revealed taxa known to produce or consume CH directly (i.e. methanogens and methanotrophs, respectively), the vast majority of identified taxa are not known to cycle CH. Each land use type had a unique subset of taxa associated with CH flux, suggesting that land use change alters CH cycling through shifts in microbial community composition. Taken together, we show that microbial composition is crucial for understanding the observed CH dynamics and that microorganisms provide explanatory power that cannot be captured by environmental variables.
• Nayfach, S., Roux, S., Seshadri, R., Udwary, D., Varghese, N., Schulz, F., Wu, D., Paez-Espino, D., Chen, I. M., Huntemann, M., Palaniappan, K., Ladau, J., Mukherjee, S., Reddy, T. B., Nielsen, T., Kirton, E., Faria, J. P., Edirisinghe, J. N., Henry, C. S., , Jungbluth, S. P., et al. (2020). A genomic catalog of Earth's microbiomes. Nature biotechnology.
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  The reconstruction of bacterial and archaeal genomes from shotgun metagenomes has enabled insights into the ecology and evolution of environmental and host-associated microbiomes. Here we applied this approach to >10,000 metagenomes collected from diverse habitats covering all of Earth's continents and oceans, including metagenomes from human and animal hosts, engineered environments, and natural and agricultural soils, to capture extant microbial, metabolic and functional potential. This comprehensive catalog includes 52,515 metagenome-assembled genomes representing 12,556 novel candidate species-level operational taxonomic units spanning 135 phyla. The catalog expands the known phylogenetic diversity of bacteria and archaea by 44% and is broadly available for streamlined comparative analyses, interactive exploration, metabolic modeling and bulk download. We demonstrate the utility of this collection for understanding secondary-metabolite biosynthetic potential and for resolving thousands of new host linkages to uncultivated viruses. This resource underscores the value of genome-centric approaches for revealing genomic properties of uncultivated microorganisms that affect ecosystem processes.
• Cueva, A., Volkmann, T. H., Van Haren, J. L., Troch, P. A., & Meredith, L. (2019). Reconciling negative soil CO2 fluxes: insights from a large-scale experimental hillslope.. Soil Systems. doi:10.3390/soilsystems3010010
• Nishisaka, C. S., Youngerman, C., Meredith, L. K., Carmo, J. B., & Navarrete, A. A. (2019). Differences in N2O fluxes and denitrification gene abundance in the wet and dry seasons through soil and plant residue characteristics of tropical tree crops. Frontiers in Environmental Science, 7, 11.
• Whelan, M. E., Wingate, L., Whelan, M., Welander, P. V., Sperber, C. V., Singer, E., Sengupta, A., Pang, E., Ogee, J., Meredith, L. K., Keiluweit, M., Bruggemann, N., Boye, K., & Berry, J. A. (2019). Soil exchange rates of COS and CO18O differ with the diversity of microbial communities and their carbonic anhydrase enzymes.. The ISME journal, 13(2), 290-300. doi:10.1038/s41396-018-0270-2
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  Differentiating the contributions of photosynthesis and respiration to the global carbon cycle is critical for improving predictive climate models. Carbonic anhydrase (CA) activity in leaves is responsible for the largest biosphere-atmosphere trace gas fluxes of carbonyl sulfide (COS) and the oxygen-18 isotopologue of carbon dioxide (CO18O) that both reflect gross photosynthetic rates. However, CA activity also occurs in soils and will be a source of uncertainty in the use of COS and CO18O as carbon cycle tracers until process-based constraints are improved. In this study, we measured COS and CO18O exchange rates and estimated the corresponding CA activity in soils from a range of biomes and land use types. Soil CA activity was not uniform for COS and CO2, and patterns of divergence were related to microbial community composition and CA gene expression patterns. In some cases, the same microbial taxa and CA classes catalyzed both COS and CO2 reactions in soil, but in other cases the specificity towards the two substrates differed markedly. CA activity for COS was related to fungal taxa and β-D-CA expression, whereas CA activity for CO2 was related to algal and bacterial taxa and α-CA expression. This study integrates gas exchange measurements, enzyme activity models, and characterization of soil taxonomic and genetic diversity to build connections between CA activity and the soil microbiome. Importantly, our results identify kinetic parameters to represent soil CA activity during application of COS and CO18O as carbon cycle tracers.
• Meredith, L. K., Boye, K., Youngerman, C., Whelan, M., Og\'ee, J., Sauze, J., & Wingate, L. (2018). Coupled Biological and Abiotic Mechanisms Driving Carbonyl Sulfide Production in Soils. Soil Systems, 2(3), 37.
• Meredith, L. K., Og\'ee, J., Boye, K., Singer, E., Wingate, L., Sperber, C., Sengupta, A., Whelan, M., Pang, E., Keiluweit, M., Br\"uggemann, N., Berry, J. A., & Welander, P. V. (2018). Soil exchange rates of COS and CO18O differ with the diversity of microbial communities and their carbonic anhydrase enzymes. ISME J..
• Whelan, M. E., Lennartz, S. T., Gimeno, T. E., Wehr, R., Wohlfahrt, G., Wang, Y., Kooijmans, L., Hilton, T. W., Belviso, S., Peylin, P., Commane, R., Sun, W. u., Chen, H., Kuai, L. e., Mammarella, I., Maseyk, K., Berkelhammer, M., Li, K., Yakir, D., , Zumkehr, A., et al. (2018). Reviews and syntheses: Carbonyl sulfide as a multi-scale tracer for carbon and water cycles. Biogeosciences, 15(12), 3625--3657.
• Belviso, S., Berkelhammer, M., Berry, J. A., Bunk, R., Campbell, J. E., Chen, H., Commane, R., Erkkila, K., Fichot, C. G., Gimeno, T. E., He, W., Hilton, T. W., Katayama, Y., Kesselmeier, J., Kitz, F., Kooijmans, L. M., Kuai, L., Launois, T., Lennartz, S. T., , Li, K., et al. (2017). Reviews and syntheses: Carbonyl sulfide as a multi-scale tracer for carbon and water cycles. Biogeosciences, 15(12), 3625-3657. doi:10.5194/bg-15-3625-2018
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  For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important one. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies. More work needs to be done to generate global coverage for OCS observations and to link this powerful atmospheric tracer to systems where fundamental questions concerning the carbon and water cycle remain.
• Wilson, R. M., Tfaily, M. M., Rich, V. I., Keller, J. K., Bridgham, S. D., Zalman, C. M., Meredith, L., Hanson, P. J., Hines, M., Pfeifer-Meister, L., Saleska, S. R., Crill, P., Cooper, W. T., Chanton, J. P., & Kostka, J. E. (2017). Hydrogenation of organic matter as a terminal electron sink sustains high CO2:CH4 production ratios during anaerobic decomposition. ORGANIC GEOCHEMISTRY, 112, 22-32.
• Meredith, L. K., Commane, R., Keenan, T. F., Klosterman, S. T., Munger, J. W., Templer, P. H., Tang, J., Wofsy, S. C., & Prinn, R. G. (2017). Ecosystem fluxes of hydrogen in a mid-latitude forest driven by soil microorganisms and plants. GLOBAL CHANGE BIOLOGY, 23(2), 906-919.
• Baker, I. T., Berry, J. A., Commane, R., Juice, S. M., Meredith, L. K., Montzka, S. A., Munger, J. W., Templer, P. H., Wofsy, S. C., & Zahniser, M. S. (2015). Seasonal fluxes of carbonyl sulfide in a midlatitude forest.. Proceedings of the National Academy of Sciences of the United States of America, 112(46), 14162-7. doi:10.1073/pnas.1504131112
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  Carbonyl sulfide (OCS), the most abundant sulfur gas in the atmosphere, has a summer minimum associated with uptake by vegetation and soils, closely correlated with CO2. We report the first direct measurements to our knowledge of the ecosystem flux of OCS throughout an annual cycle, at a mixed temperate forest. The forest took up OCS during most of the growing season with an overall uptake of 1.36 ± 0.01 mol OCS per ha (43.5 ± 0.5 g S per ha, 95% confidence intervals) for the year. Daytime fluxes accounted for 72% of total uptake. Both soils and incompletely closed stomata in the canopy contributed to nighttime fluxes. Unexpected net OCS emission occurred during the warmest weeks in summer. Many requirements necessary to use fluxes of OCS as a simple estimate of photosynthesis were not met because OCS fluxes did not have a constant relationship with photosynthesis throughout an entire day or over the entire year. However, OCS fluxes provide a direct measure of ecosystem-scale stomatal conductance and mesophyll function, without relying on measures of soil evaporation or leaf temperature, and reveal previously unseen heterogeneity of forest canopy processes. Observations of OCS flux provide powerful, independent means to test and refine land surface and carbon cycle models at the ecosystem scale.
• Rockmann, T., Quiza, L., Popa, M. E., Meredith, L. K., Lalonde, I., Khdhiri, M., Hesse, L., & Constant, P. (2015). Soil carbon content and relative abundance of high affinity H2-oxidizing bacteria predict atmospheric H2 soil uptake activity better than soil microbial community composition. Soil Biology & Biochemistry, 85, 1-9. doi:10.1016/j.soilbio.2015.02.030
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  Soil–atmosphere exchange of H2 is controlled by gas diffusion and the microbial production and oxidation activities in soil. Among these parameters, the H2 oxidation activity catalyzed by soil microorganisms harboring high affinity hydrogenase is the most difficult variable to parameterize because it is influenced by many unknown edaphic factors that shape microbial community structure and function. Here we seek to formulate a model combining microbiological and physicochemical variables to predict the H2 oxidation rate (u) in soil. Soil sample replicates collected from a grassland and three forests exhibited different H2 oxidation potentials. We examined the microbial community structure based on ribotyping analysis, the relative abundance of high affinity H2-oxidizing bacteria (HOB) estimated by qPCR and soil physicochemical characteristics as predictors for u. A single linear regression parameterized by total carbon content and a multiple linear regression using total carbon content and HOB relative abundance in soil explained 66 and 92% of the variance in u, respectively. Microbial community composition based on 16S rRNA gene pyrosequencing profiles was not a reliable predictor for u. Indeed, we found that HOB are members of the rare biosphere, comprising less than 1% of total bacteria as estimated by qPCR. We confirmed this relationship of u with total carbon content and HOB by an independent soil survey of 14 samples collected from maize monocultures, grasslands, deciduous forests and larch plantations. Observations made from both soil surveys thus were combined to build a predictive model for u parameterized with total carbon content and HOB relative abundance. Our results show that molecular biogeochemistry is a potential approach to improve performance of classical H2 surface flux models which estimate u empirically without considering variation in HOB distribution and activity in soil.
• Hall, B. D., Chatterjee, A., Doherty, S. O., Ganesan, A. L., Hall, B. D., Harth, C. M., Manning, A. J., Meredith, L. K., Muhle, J., O'doherty, S., Prinn, R. G., Salameh, P. K., Weiss, R. F., & Young, D. (2013). The variability of methane, nitrous oxide and sulfur hexafluoride in Northeast India *. Atmospheric Chemistry and Physics, 13(21), 10633-10644. doi:10.5194/acp-13-10633-2013
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  Abstract. High-frequency atmospheric measurements of methane (CH4), nitrous oxide (N2O) and sulfur hexafluoride (SF6) from Darjeeling, India are presented from December 2011 (CH4)/March 2012 (N2O and SF6) through February 2013. These measurements were made on a gas chromatograph equipped with a flame ionization detector and electron capture detector, and were calibrated on the Tohoku University, the Scripps Institution of Oceanography (SIO)-98 and SIO-2005 scales for CH4, N2O and SF6, respectively. The observations show large variability and frequent pollution events in CH4 and N2O mole fractions, suggesting significant sources in the regions sampled by Darjeeling throughout the year. By contrast, SF6 mole fractions show little variability and only occasional pollution episodes, likely due to weak sources in the region. Simulations using the Numerical Atmospheric dispersion Modelling Environment (NAME) particle dispersion model suggest that many of the enhancements in the three gases result from the transport of pollutants from the densely populated Indo-Gangetic Plains of India to Darjeeling. The meteorology of the region varies considerably throughout the year from Himalayan flows in the winter to the strong south Asian summer monsoon. The model is consistent in simulating a diurnal cycle in CH4 and N2O mole fractions that is present during the winter but absent in the summer and suggests that the signals measured at Darjeeling are dominated by large-scale (~100 km) flows rather than local (

Proceedings Publications

• Meredith, L. K., Brodie, E., Krechmer, J. E., & Jardine, K. (2021). Microbial sources and sinks of volatile organic compounds (VOCs). In AGU Fall Meeting 2021.
• Purser, G., Kreuzwieser, J., Ingrisch, J., Meeran, K., Loaiza, J. G., Daber, E., Ladd, S. N., Meredith, L., & Werner, C. (2020, 4). Volatile organic compound fluxes across the soils of a rainforest ecosystem during a simulated drought experiment. In European Geophysical Union 2020.
• Andrews, H., Gil-Loaiza, J., Honeker, L. K., Clark, M., Ladd, N., Werner, C., Van, H., Tfaily, M. M., Shorter, J. H., Roscioli, J. R., & Meredith, L. (2021). Microbial controls of nitrous oxide pulses in rewetted forest soils: An integrated-omic and isotopic approach. In AGU Fall Meeting 2021.
• Blomdahl, D., Meredith, L. K., Werner, C., Ladd, S. N., Langford, B., Nemitz, E., & Misztal, P. K. (2021). Factor Analysis of VOC Concentrations Over a Vertical Gradient Within Biosphere 2 Rainforest Elucidates Strong Microbial Sources Near Ground Level. In AGU Fall Meeting 2021.
• Geffre, P., Krechmer, J., Hagan, D. H., Cross, E., Roscioli, J. R., & Meredith, L. K. (2021). Using a Novel Sensor for Detection of Subsurface Volatile Organic Compounds. In AGU Fall Meeting 2021.
• Graves, K., Honeker, L. K., Geffre, P., Riemer, K., Tfaily, M. M., Krechmer, J., & Meredith, L. K. (2021). Microbial Volatile Organic Compounds: Important but Undetected. In AGU Fall Meeting 2021.
• Hildebrand, G., Werner, C., Meredith, L. K., & Tfaily, M. M. (2021). Microbial Community and Metabolomic Response to Drought and Ecological Stress at the Biosphere 2 Tropical Rainforest. In AGU Fall Meeting 2021.
• Honeker, L., Pugliese, G., Ingrisch, J., Fudyma, J., Gil-Loaiza, J., Carpenter, E., Singer, E., Hildebrand, G., Shi, L., Daber, L. E., & Meredith, L. (2021). Effect of drought on soil microbial metabolisms driving carbon allocation and volatile organic compound cycling in the tropical rainforest at Biosphere 2. In American Geophysical Meeting 2021.
• K\"ubert, A., K\"uhnhammer, K., Bamberger, I., Daber, E., De, L. J., Bailey, K., Hu, J., Nemiah Ladd, S., Meredith, L., Haren, J., & others, . (2021). Tropical rainforests under severe drought stress: distinct water use strategies among and within species. In EGU General Assembly Conference Abstracts.
• Krechmer, J., Meredith, L. K., Gil-Loaiza, J., Clark, M., Grigory, J., Demieville, J., Pauli, D., Lunny, E. M., Shorter, J. H., & Roscioli, J. R. (2021). Real-Time in-situ Measurements of Subsurface Volatile Organic Compounds as Tracers for Crop Signaling. In AGU Fall Meeting 2021.
• Lunny, E., Roscioli, J. R., Shorter, J. H., Krechmer, J., Meredith, L. K., Gil-Loaiza, J., Clark, M., Grigory, J., Pauli, D., & Demieville, J. (2021). Subsurface measurements of nitrogen dynamics in agricultural soil. In AGU Fall Meeting 2021.
• Meredith, L. K., Brodie, E., Krechmer, J., & Jardine, K. (2021). Microbial Sources and Sinks of Volatile Organic Compounds (VOCs) I eLightning. In AGU Fall Meeting 2021.
• Meredith, L. K., Werner, C., Ladd, N., Pugliese, G., Honeker, L. K., Ingrisch, J., Van, H., & Williams, J. (2021). Soil-microbe-plant feedbacks to ecosystem drought in a model tropical rainforest ecosystem. In AGU Fall Meeting 2021.
• Newton, A., U'Ren, J., Clark, M., Hunt, R., Nickerson, M., Commane, R., Baker, I. T., & Meredith, L. K. (2021). Understanding the Effect of Aboveground Vegetation Composition on Carbonyl Sulfide and Carbon Dioxide Fluxes in Alaskan Tundra and Boreal Biomes.. In AGU Fall Meeting 2021.
• Pugliese, G., Ingrisch, J., Kl\"upfel, T., Meeran, K., Purser, G., Gil, L. J., Haren, J., Kreuzwieser, J., Ladd, N., Meredith, L., & others, . (2021). Effects of drought conditions on VOC soil fluxes within the rainforest mesocosm of Biosphere 2. In EGU General Assembly Conference Abstracts.
• Ronan, T., Honeker, L. K., Gil-Loaiza, J., Tfaily, M. M., Roscioli, J. R., Shorter, J. H., Krechmer, J., & Meredith, L. K. (2021). Predicting volatile organic compound (VOC) production and uptake locations using depth-resolved concentrations for a better understanding of the soil metabolome. In AGU Fall Meeting 2021.
• Roscioli, J. R., Shorter, J. H., Lunny, E., Herndon, S. C., Gomez-Casanovas, N., DeLucia, E. H., Blanc-Betes, E., Byck, P., & Meredith, L. K. (2021). Connecting above-ground greenhouse gas fluxes with subsurface nutrient cycling at an intensively-managed cattle grazing pasture. In AGU Fall Meeting 2021.
• Tfaily, M. M., Meredith, L. K., Hildebrand, G., Honeker, L. K., Fudyma, J., Daber, L. E., Hoyt, D. W., Flowers, S., Gil-Loaiza, J., K\"ubert, A., & others, . (2021). Spatial metabolic profiling in roots reveals plant specific responses to drought at the Biosphere 2 tropical rainforest. In AGU Fall Meeting 2021.
• Werner, C., Meredith, L. K., Ladd, S. N., Ingrisch, J., K\"ubert, A., & Van, H. (2021). Plant functional groups and soil interactions drive ecosystem fluxes during drought and recovery-insights from an ecosystem-scale isotope labelling experiment. In AGU Fall Meeting 2021.
• Werner, C., Meredith, L., Ladd, N., Ingrisch, J., Kuebbert, A., & van Haren, J. (2021). Diverse functional responses drive ecosystem drought impact and recovery-insights from an ecosystem-scale drought experiment. In EGU General Assembly Conference Abstracts.
• Bailey, K., Hu, J., Warner, C., Ladd, N., Meredith, L., Haren, J., Beyer, M., Lehman, M., & Prohaska, N. (2020). How does drought affect the $\delta$18O cellulose record? A Biosphere 2 experiment.. In EGU General Assembly Conference Abstracts.
• Bamberger, I., Daber, L. E., Gil, L. J., Purser, G., De, L. J., Nemiah Ladd, S., Meredith, L., Kreuzwieser, J., & Werner, C. (2020). Drought effects on the carbon balance and VOC emissions of a tropical rainforest ecosystem. In EGU General Assembly Conference Abstracts.
• Blomdahl, D., Meredith, L., Werner, C., Ladd, N., Langford, B., Nemitz, E., Haren, J., Bamburger, I., Purser, G., Byron, J., & others, . (2020). Biogenic VOC emissions under drought and temperature stress. In EGU General Assembly Conference Abstracts.
• Byron, J., Werner, C., Ladd, N., Meredith, L., Purser, G., & Williams, J. (2020). Changes in chiral monoterpenes during drought in a rainforest reveal distinct source mechanisms. In EGU General Assembly Conference Abstracts.
• Daber, L. E., Bamberger, I., Nemiah Ladd, S., Kreuzwieser, J., Fudyma, J., Gil, L. J., De, L. J., Shi, L., Bai, X., Purser, G., & others, . (2020). Understanding drought induced responses in leaf and root CO2 and VOC fluxes through position specific isotope labelling. In EGU General Assembly Conference Abstracts.
• Gil, L. J., Meredith, L., Krechmer, J., Claflin, M., Roscioli, R., & Shorter, J. (2020). Rhizosphere Volatile Organic Compounds: A real-time approach using diffusive soil probes on a controlled Tropical Rainforest. In EGU General Assembly Conference Abstracts.
• Haren, J., Kuhnhammer, K., Kuebert, A., Beyer, M., Tuller, M., Babaeian, E., Hu, J., Dubbert, M., Meredith, L., & Werner, C. (2020). Water cycling (pools and movement) through an enclosed tropical forest in response to drought.. In EGU General Assembly Conference Abstracts.
• Ingrisch, J., Meeran, K., K\"ubert, A., Ladd, N., Haren, J., Werner, C., Meredith, L., & Bahn, M. (2020). Tracing recent carbon from photosynthesis to stem and soil respiration in an experimental tropical rainforest in response to drought. In EGU General Assembly Conference Abstracts.
• K\"ubert, A., K\"uhnhammer, K., Bamberger, I., Daber, E., De, L. J., Bailey, K., Hu, J., Nemiah Ladd, S., Meredith, L., Haren, J., & others, . (2020). Above ground response of rainforest functional groups to experimental drought. In EGU General Assembly Conference Abstracts.
• Kerman, S., Bailey, K., Haren, J., K\"ubert, A., K\"uhnhammer, K., Werner, C., Ladd, N., Meredith, L., & Hu, J. (2020). Plant Water Relation and Drought: Relationship Between Plant Water Potential and Relative Leaf Water Content in Different Tropical Plants. In EGU General Assembly Conference Abstracts.
• Kuehnhammer, K., Haren, J., Kuebert, A., Dubbert, M., Ladd, N., Meredith, L., Werner, C., & Beyer, M. (2020). Tracing dynamic water uptake and transport from root to canopy by online monitoring of water isotopes in an enclosed tropical forest in response to drought. In EGU General Assembly Conference Abstracts.
• Meredith, L. K., Krechmer, J. E., Gil-Loaiza, J., Roscioli, J. R., Shorter, J. H., Claflin, M., Daber, L. E., Fudyma, J., Ingrisch, J., Meeran, K., & others, . (2020). Exploring the role of volatile organic compounds in the rhizosphere interactome. In AGU Fall Meeting 2020.
• Meredith, L., Commane, R., Baker, I., Gil-Loaiza, J., Haren, J., Ladd, N., & Werner, C. (2020). Carbonyl sulfide reflections of leaf and ecosystem processes in a tropical rainforest under controlled drought. In EGU General Assembly Conference Abstracts.
• Roscioli, J., Shorter, J., Krechmer, J., Meredith, L., & Gil, L. J. (2020). Exploring The Birch Effect In The Subsurface Using Diffusive Soil Probes. In EGU General Assembly Conference Abstracts.
• Schaik, E., Mondy, S., Lelievre, M., Martin, M., Perrin, S., Meredith, L., Kaisermann, A., Jones, S., Rue, O., Loux, V., & others, . (2020). Revealing how nitrogen fertilisation regulates the fluxes of COS and CO2 between soil communities and the atmosphere using a functional metagenomic and metatranscriptomic approach. In EGU General Assembly Conference Abstracts.
• Shorter, J., Roscioli, J., Meredith, L., & Gil-Loaiza, J. (2020). Soil Biogeochemical Response to Drought Conditions in the Biosphere 2 Rainforest. In EGU General Assembly Conference Abstracts.
• Werner, C., Ladd, N. S., & Meredith, L. (2020). Tracing ecosystem scale interactions of volatile organic compound (VOC) and CO2 emissions by position-specific and whole ecosystem isotope labelling. In EGU General Assembly Conference Abstracts.
• Buzzard, V., Gil-Loaiza, J., Meredith, L. K., & Youngerman, C. (2019). Green infrastructure influences on microbial community composition in arid urban environments. In AGU Fall Meeting 2019.
• Chavarria, H. I., Lopez, J. M., Hunt, E., Meredith, L. K., Van, H., & Dontsova, K. (2019). Biosphere 2: The Changes of Soil Composition and Properties in Time in the Rainforest Biome. In AGU Fall Meeting 2019.
• Chee, T., AminiTabrizi, R., P\'erez, R. C., Gieschen, H., Meredith, L. K., Fudyma, J., & Tfaily, M. M. (2019). Comparison of Soil Organic Matter (SOM) Composition in the soil column at the Biosphere 2 Tropical Rainforest. In AGU Fall Meeting 2019.
• Cueva, A., Volkmann, T. H., Haren, J., Troch, P. A., & Meredith, L. K. (2019). Net exchange of carbonyl sulfide, carbon monoxide, and carbon dioxide in a highly oligotrophic basaltic soil: a mesocosm study.. In Geophysical Research Abstracts, 21.
• Daber, L. E., Bramberger, I., Ladd, N., Kreuzwieser, J., Misztal, P. K., Meredith, L. K., & Werner, C. (2019). Plant carbon allocation in tropical forests under drought stress-Shifting the balance between primary and secondary metabolism such as CO 2 and VOC emissions. In AGU Fall Meeting 2019.
• Gil-Loaiza, J., Meredith, L. K., Roscioli, J. R., Shorter, J. H., & Krechmer, J. E. (2019). Coupling new soil probes and high-resolution trace gas isotopomer measurement systems: evaluating feasibility in controlled soil columns. In AGU Fall Meeting 2019.
• Ingrisch, J., Meeran, K., Ladd, N., Van, H., Werner, C., Meredith, L. K., & Bahn, M. (2019). Tracing recent carbon from photosynthesis to stem and soil respiration in an experimental tropical rainforest in response to drought. In AGU Fall Meeting 2019.
• Krechmer, J., Roscioli, J. R., Shorter, J. H., Claflin, M. S., Gil-Loaiza, J., Meredith, L. K., Lerner, B. M., & Canagaratna, M. R. (2019). Exploring Isotopically-Resolved Subsurface and Root Volatile Organic Compound Signatures at Biosphere 2. In AGU Fall Meeting 2019.
• Ladd, N., Nelson, D. B., Bramberger, I., Daber, L. E., Meredith, L. K., Kahmen, A., Schubert, C. J., & Werner, C. (2019). Position specific 13 C pyruvate labeling demonstrates how drought responses affect hydrogen isotope fractionation during plant lipid biosynthesis. In AGU Fall Meeting 2019.
• Lujano, A. R., Ladd, N., Bamberger, I., Byron, J., Kreuzwieser, J., Werner, C., & Meredith, L. K. (2019). Diversity of Leaf Secondary Compounds (Lipid and Volatiles) of Six Tropical Plant Species. In AGU Fall Meeting 2019.
• Mart\'\inez-Sosa, P., Meredith, L. K., & Tierney, J. E. (2019). Microbial Community Drives BrGDGT Response to Environmental Changes in Freshwater Microcosms. In AGU Fall Meeting 2019.
• Meredith, L. (2019). From Soils to the Atmosphere: Characterizing Abiotic and Biotic Interactions That Dictate the Microbial Impact on Soil and Atmospheric Chemistry.. In SSSA International Soils Meeting.
• Meredith, L. K. (2019). Unearthing Links between Microbial Genomics and Trace Gas Cycling. In AGU Fall Meeting 2019.
• Meredith, L. K., Gil-Loaiza, J., Roscioli, J. R., Shorter, J. H., Krechmer, J. E., Tfaily, M. M., U'Ren, J., Misztal, P. K., Singer, E., Commane, R., & others, . (2019). Integrating Soil Genomics into the Study of Biosphere-Atmosphere Trace Gas Fluxes. In AGU Fall Meeting 2019.
• Meredith, L. K., Werner, C., & Ladd, N. (2019). Opportunities and Challenges for Revealing Ecosystem Interactions through Whole-Ecosystem Stable Isotope Labeling and Experimentation: Lessons Learned from the Biosphere 2 Water, Atmosphere, and Life Dynamics Campaign. In AGU Fall Meeting 2019.
• Meredith, L., Cueva, A., Volkmann, T., U'Ren, J., Singer, E., Haren, J., & Troch, P. (2019). Carbonyl sulfide (COS) as a tracer for plant carbon and water cycling: how do recent models from COS science perform in a controlled ecosystem?. In Geophysical Research Abstracts, 21.
• Meredith, L., Youngerman, C., Sengupta, A., Troch, P., & Volkmann, T. (2019). Noninvasive methods for dynamic mapping of microbial populations across the landscape.. In Geophysical Research Abstracts, 21.
• Ogee, J., Wingate, L., Cuntz, M., Jones, S. P., Meredith, L., Sauze, J., Wohl, S., Kaisermann, A., Launois, T., & Genty, B. (2019). New estimates of global land photosynthesis using updated theories of CO2-H2O oxygen isotope exchange rates in land water pools.. In Geophysical Research Abstracts, 21.
• P\'erez, R. C., AminiTabrizi, R., Chee, T., Gieschen, H., Meredith, L. K., Fudyma, J., & Tfaily, M. M. (2019). A Journey from Roots to Bulk Soil: Organic Matter Characterization in the Biosphere 2 Tropical Rainforest. In AGU Fall Meeting 2019.
• Roscioli, J. R., Shorter, J. H., Krechmer, J. E., Meredith, L. K., & Gil-Loaiza, J. (2019). Exploring Fast Nitrogen, Carbon, and VOC Dynamics During Simulated Drought and Rewetting Events. In AGU Fall Meeting 2019.
• Roscioli, J., Shorter, J., Meredith, L., Loaiza, J. G., & Volkmann, T. (2019). Toward Spatially Resolved Mapping of Subsurface Biological Processes Using Isotopic Signatures.. In Geophysical Research Abstracts, 21.
• Sengupta, A., Barberan, A., Stegen, J., Volkmann, T., Dontsova, K., Neilson, J. W., Chorover, J., Maier, R. M., Troch, P. A., & Meredith, L. (2019). Structural and Functional Response of Microbial Community in an Oligotrophic Basalt Soil System to Shifts in Rainfall Regimes.. In SSSA International Soils Meeting.
• Shorter, J. H., Roscioli, J. R., Meredith, L. K., & Gil-Loaiza, J. (2019). Tracking Dynamics of Soil Nitrogen Cycling with High Temporal Resolution. In AGU Fall Meeting 2019.
• Spivey, P., Buzzard, V., Loaiza, J. G., & Meredith, L. (2019). An Examination of the Count, Viability, and Characterization of Microbes within the Rainwater Supply of the Landscape Evolution Observatory to Identify Impacts on the Soil Microbiome.. In Geophysical Research Abstracts, 21.
• Talkington, H., Buzzard, V., & Meredith, L. K. (2019). Water Harvesting Techniques Result in Varied Decomposition Rates in Soil. In AGU Fall Meeting 2019.
• Van, H., Kuehnhammer, K., K\"ubert, A., Dubbert, M., Tuller, M., Babaeian, E., Beyer, M., Meredith, L. K., & Werner, C. (2019). Water cycling (pools and movement) through an enclosed tropical forest in response to drought.. In AGU Fall Meeting 2019.
• Werner, C., Daber, L. E., Bramberger, I., Ladd, N., Y\'a\~nez-Serrano, A. M., Fasbender, L., Misztal, P. K., Meredith, L. K., & Kreuzwieser, J. (2019). Link between plant volatile organic compound (VOC) emissions and CO 2 metabolism from sub-molecular to ecosystem scales by 13 C-labelling. In AGU Fall Meeting 2019.
• Wingate, L., Og\'ee, J., Kaisermann, A., Sauze, J., Jones, S., Wohl, S., Meredith, L., Whelan, M., Launois, T., & Cuntz, M. (2019). Scaling the fluxes of carbonyl sulphide (COS) between soils and the atmosphere from the microcosm to the globe.. In Geophysical Research Abstracts, 21.
• Youngerman, C., Sengupta, A., Volkmann, T., Troch, P. A., Spivey, P., & Meredith, L. (2019, April). Assessing changes in landscape-level microbial communities with noninvasive methods for dynamic mapping. In Joint Genome Institute Annual User Meeting.

Presentations

• Meredith, L. (2021). Belowground stable isotope soil gas probing to resolve controls on nitrogen use efficiency of a sorghum bioenergy crop. EMSL Integration MeetingDepartment of Energy.
• Meredith, L. (2021). Genetic drivers of microbial carbonyl sulfide metabolism: how a tiny enzyme may unlock the carbon balance of the atmosphere. Genetics GIDP SeminarUniversity of Arizona.
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  Carbonic anhydrase (CA) enzymes catalyze critical carbon concentrating functions in plants and microbes that drive global photosynthesis. Importantly, CA also hydrolyze carbonyl sulfide (COS), a structural analog to carbon dioxide (CO2), positioning COS as a tracer for photosynthesis. CA are diverse, ancient, and widely distributed enzymes, and major gaps persist in our understanding of the types of CA that drive significant uptake of these trace gases gases by the biosphere. In our work, we combine genome database mining, kinetic assays, and field surveys to connect the genetic diversity of CA to biological communities and predict their influence on atmospheric carbon at large scales.
• Meredith, L. (2021). Sensitivity of soil microbial volatile organic compound metabolism to drought and rewet. ENVS Seminar SeriesUniversity of Arizona.
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  Soil microbes cycle volatile organic compounds (VOCs) as metabolites and signaling molecules, and VOCs represent the volatile portion of their metabolome coined the ‘volatilome’. Soil sources and sinks of VOCs contribute to ecosystem-scale interactions with the atmosphere where VOCs influence air quality and cloud formation. Identifying microbial VOC pathways and their behavior in the environment is foundational to understanding and predicting soil VOC fluxes, including their responses to environmental drivers such as drought. To explore the sensitivity of microbial soil VOC metabolism to drought, we conducted an ecosystem-scale drought in the tropical rainforest biome at the University of Arizona Biosphere 2 during the 5-month Water, Atmosphere, and Life Dynamics (WALD) campaign. Within the context of this campaign, we designed experiments to quantify soil VOC fluxes via autochambers and subsurface soil VOC concentrations using our recently developed non-invasive, online soil gas sampling approach. Moreover, to identify the up- and down-regulation of microbial VOC cycling, we used a combination of 13C stable isotope labeling and ‘omics approaches that characterize the gene content (metagenomes), gene expression (metatranscriptomes), and organic matter composition (metabolomics) of soil. We observed dynamic and diverse patterns in soil VOC fluxes in response to drought and rewet. Soil microbes consumed atmospheric isoprene and monoterpenes. Other VOCs exhibited a strong flux enhancement in response to rewetting, including both increased emissions (e.g., dimethyl sulfide) and uptake (e.g. acetone). Stable isotope labeling revealed surprising up-regulation of VOC-producing fermentation pathways during drought. With the ongoing integrative analysis of these data, we aim to contribute to the growing understanding of microbial VOC pathways in soil and their sensitivity to shifts in ecosystem moisture conditions.
• Meredith, L. (2021). The belowground perspective on soil microbial trace gas cycling. iLEAPS symposium.
• Meredith, L. (2021, April). Revealing ecosystem interactions through novel whole-ecosystem online stable isotope labeling and measurement approaches. Ecology Seminar. remote: Lawrence Berkeley National Lab.
• McIntyre, B., Clover, M., Moore, L., Kreuzwieser, J., Meredith, L., & Uren, J. M. (2020, January). Endophytic Fungi in the Biosphere 2 Tropical Rainforest. UBRP Research ConferenceUniversity of Arizona.
• Dontsova, K. M., Van Haren, J. L., Meredith, L., Hunt, E., Lopez, J. M., & Chavarria, H. I. (2019, December 2019). EP53F-2209: Biosphere 2: The Changes of Soil Composition and Properties in Time in the Rainforest Biome.. American Geophysical Union Fall Meeting. San Francisco, CA: American Geophysical Union.
• Meredith, L. (2018, August). Microbe-mediated trace gas fluxes;  linking ecosystem genomics to atmospheric composition. Seminar at Technical University of Munich. Munich, Germany.
• Meredith, L. (2019, April). Biosphere 2 Science: Large Scale Research with Big Data Needs. TRIPODS Data Science GroupUniversity of Arizona.
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  The University of Arizona uses the biomes and experimental systems at Biosphere 2 (B2), including the Tropical Rainforest, Ocean, and Landscape Evolution Observatory (LEO), to study ecosystem responses to controlled disturbances. The large scale of this research infrastructure enables controlled ecosystem studies at realistic spatial scales with high observational density—effectively bridging the gap between laboratory and field studies. Observations of the B2 systems is facilitated by dense sensor networks that stream long-term continuous data, for example over 1 million data points are read from nearly 2,000 sensors each day at LEO. These data are integrated with discrete in situ and or lab-derived observations, for example soil chemistry and microbial community composition, to extend the types of interdisciplinary research questions that can be addressed. Even on a routine basis, integrating the interdisciplinary and heterogenous data generated at B2 is a challenge, and this task is even more daunting during large research campaigns in which additional instrumentation, expertise, and collaborators generate massive data sets to describe ecosystem response to controlled experiments over relatively short periods. As an example, the upcoming B2 Water, Atmosphere, and Life Dynamics (B2 WALD) campaign will bring together an international team to constrain the Tropical Rainforest response to drought with continuous in situ datasets (online gas analysis and environmental sensors), with discrete in situ measurements (portable gas and leaf spectral analysis) and discrete lab-based insights (trapped gases, leaf traits, soil & water chemistry, multi-omics datasets). Uniting these data is a significant challenge, but an essential basis to derive the most impactful results from experimentation at B2. In this talk, I will describe current and planned experiments leading to data generation at Biosphere 2 with the goal of stimulating discussions on how current approaches in computer science, mathematics, and statistics may enhance scientific outcomes in this unique facility.
• Meredith, L. (2019, May). Linking microbial genes to emergent outcomes in soil systems. ENS School of Biological Sciences Seminar Series. Paris, France: École normale supérieure.
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  Abstract: Microbes encode for vast genetic potential, yet predicting functional outcomes of microbial communities is challenging, especially in soils where highly diverse (thousands to millions of taxa) and abundant (109 cells per gram of soil) microbial populations reside. While significant advances have been made in profiling microbial communities via their genomic signatures using multi-omics techniques, gaps in gene-to-function links and their representation in models exist. For example, although microbes catalyze trace gas production and consumption of greenhouse gases (e.g., CO2, CH4, N2O), atmospheric tracers (e.g., OCS, 18O-CO2), and microbial signalling compounds (e.g., hundreds of volatile organic compounds), the key enzymes (if known) often have poorly resolved functional diversity and phylogenetic distribution. Furthermore, even when gene-to-function links are resolved in reductionist experiments, soil gas fluxes are poorly predicted from soil genomic data, which is often presumed to be related to soil heterogeneity and mismatches in spatial and temporal scales (e.g., static -omics vs real time gas fluxes). To address these challenges, we use experimentation across scales to constrain genetic traits for trace gas metabolisms, develop soil gas sensors to better match microbial and gas flux data, and leverage constrained and controlled model ecosystems to advance our ability to scale from genes to ecosystems. In this talk, I will present recent research illustrating these approaches to build predictive understanding of biosphere-atmosphere trace gas exchange and soil microbial function.
• Cueva, A., Meredith, L., & Troch, P. A. (2018, May). Biosphere 2 – Landscape Evolution Observatory: Un experimento a gran escala. Programa Mexicano del Carbono 9th Simposio Internacional del Carbono en Mexico. Sonora, Mexico.
• Kaisermann, A., Ogee, J., Sauze, J., Wohl, S., Meredith, L., Lanois, T., & Wingate, L. (2018, April). "Disentangling the rates of carbonyl sulphide (COS) production and consumption and their dependency with soil properties across biomes and land use types". European Geophysical Union. Vienna, Austria.
• Meredith, L. (2018, January). Using Trace Gases to Track Interactions Between Life and the Environment in Modern Soils and Evolving Landscapes. Geobiology Gordon Research Conference. Galveston, Texas.
• Meredith, L. (2018, October). Microbe-mediated trace gas fluxes;  linking ecosystem genomics to atmospheric composition. Ecosystem Genomics Seminar Series. Tucson, AZ.
• Meredith, L., Buzzard, V., Gil Loaiza, J., Youngerman, C., & Thorne, D. (2018, October). Urban Rainwater Harvesting. Impacts on Soil Microbial Communities and Function. Research Insights in Semiarid Ecosystems Symposium. Tucson, AZ.
• Meredith, L., Sengupta, A., Youngerman, C., Troch, P. A., & Volkmann, T. H. (2018, August). Noninvasive methods for dynamically mapping microbial populations across an artificial landscape. ISME General Assembly. Leipzig, Germany.
• Meredith, L. (2017, October). Microbe-mediated trace gas fluxes: linking ecosystem genomics to atmospheric composition. Geosciences ColloquiumGeosciences, University of Arizona.
• Meredith, L. (2017, September). Biosphere-atmosphere trace-gas flux measurements of microbe- mediated biogeochemical cycles. Hydrology and Atmospheric Sciences Seminar SeriesHAS.
• Volkmann, T. H., Van Haren, J. L., Kim, M., Harman, C. J., Pangle, L., Meredith, L., & Troch, P. A. (2017, Dec). Real-time isotope monitoring network at the Biosphere 2 Landscape Evolution Observatory resolves meter-to-catchment scale flow dynamics. AGU International Annual Meeting. New Orleans, LA.
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  Stable isotope analysis is a powerful tool for tracking flow pathways, residence times, and the partitioning of water resources through catchments. However, the capacity of stable isotopes to characterize catchment hydrological dynamics has not been fully exploited as commonly used methodologies constrain the frequency and extent at which isotopic data is available across hydrologically-relevant compartments (e.g. soil, plants, atmosphere, streams). Here, building upon significant recent developments in laser spectroscopy and sampling techniques, we present a fully automated monitoring network for tracing water isotopes through the three model catchments of the Landscape Evolution Observatory (LEO) at the Biosphere 2, University of Arizona. The network implements state-of-the-art techniques for monitoring in great spatiotemporal detail the stable isotope composition of water in the subsurface soil, the discharge outflow, and the atmosphere above the bare soil surface of each of the 330-m2 catchments. The extensive valving and probing systems facilitate repeated isotope measurements from a total of more than five-hundred locations across the LEO domain, complementing an already dense array of hydrometric and other sensors installed on, within, and above each catchment. The isotope monitoring network is operational and was leveraged during several months of experimentation with deuterium-labelled rain pulse applications. Data obtained during the experiments demonstrate the capacity of the monitoring network to resolve sub-meter to whole-catchment scale flow and transport dynamics in continuous time. Over the years to come, the isotope monitoring network is expected to serve as an essential tool for collaborative interdisciplinary Earth science at LEO, allowing us to disentangle changes in hydrological behavior as the model catchments evolve in time through weathering and colonization by plant communities.

Poster Presentations

• Van Haren, J. L., Kuhnhammer, K., Kuebert, A., Beyer, M., Tuller, M., Babaeian, E., Hu, J., Dubbert, M., Meredith, L., Werner, C., Werner, C., Meredith, L., Dubbert, M., Hu, J., Babaeian, E., Tuller, M., Beyer, M., Kuebert, A., Kuhnhammer, K., & Van Haren, J. L. (2020, May). Water Cycling (Pools and Movement) Through an Enclosed Tropical Forest in Response to Drought. EGU General Assembly. Virtual: European Geosciences Union.
• Meredith, L., & Tfaily, M. (2019, Fall). Soil Genomics into the Study of Biosphere-Atmosphere Trace Gas Fluxes. AGU. SF.
• Cueva, A., Volkmann, T. H., Troch, P. A., & Meredith, L. (2018, March). Variability and Environmental Controls of Negative Soil CO2 Fluxes: Insights from a Large Scale Experimental Hillslope. CALS Poster Forum. Tucson, AZ.
• Gil Loaiza, J., Buzzard, V., Youngerman, C., & Meredith, L. (2018, March). Green Infrastructure Practices to Restore Urban Soils: Linking Soil Parameters and Microbial Communities. CALS Poster Forum. Tucson, AZ.
• Gil Loaiza, J., Roscioli, R., Vokmann, T. H., Shorter, J., & Meredith, L. (2018, October). In situ trace gas measurement system. São Paulo School of Advanced Methane Science. Ilhabela, Brazil.
• Hunt, R., Buzzard, V., Gil Loaiza, J., & Meredith, L. (2018, July). Seasonal differences of soil physical and chemical properties influenced by water treatment source. KEYS high school poster forum. Tucson, AZ.
• Kellogg, G., & Meredith, L. (2018, January). "IMPLICATIONS OF EDAPHIC DRIVERS ON SOIL MICROBIAL COMMUNITIES ". "UBRP conference and Native American Cancer Prevention (NACP) conference. Tucson, AZ.
• Meredith, L., Troch, P. A., Maier, R. M., Chorover, J. D., Neilson, J. W., Dontsova, K. M., Volkmann, T., Stegen, J., Barberan, A., & Sengupta, A. (2018, August). Structural and functional response of incipient basaltic microbial community to shifts in soil moisture regime. Goldschmidt. Boston, MA.
• Meredith, L., Troch, P. A., Maier, R. M., Chorover, J. D., Neilson, J. W., Dontsova, K. M., Volkmann, T., Stegen, J., Barberan, A., Sengupta, A., Meredith, L., Troch, P. A., Maier, R. M., Chorover, J. D., Neilson, J. W., Dontsova, K. M., Volkmann, T., Stegen, J., Barberan, A., , Sengupta, A., et al. (2019, January). Structural and Functional Response of Microbial Community in an Oligotrophic Basalt Soil System to Shifts in Rainfall Regimes. Soil Science Society of America (SSSA) International Soils Meeting “Soils Across Latitudes”. San Diego, CA: Soil Science Society of America.
• Pappas, J., Cueva, A., Volkmann, T. H., Troch, P. A., & Meredith, L. (2018, August). Net soil exchange of CO2 and CO in a mesocosm experiment with incipient basaltic tephra. UROC and AZDM poster presentations. Tucson, AZ.
• Pedrinho, A., Meredith, L., Rodrigues, J., Nusslein, K., Bohannan, B., & Siu Mui, T. (2018, Spring). Land use change alters the denitrification process in the Amazon Rainforest. JGI User Meeting. San Francisco, CA.
• Singer, E., Hartmann, W., Chong, L., Meredith, L., & Wolke, T. (2018, July). Metals control microbially mediated carbon sequestration in Mediterranean grassland top soil. International Society of Microbial Ecology General Assembly. Leipzig, Germany.
• Spivey, P., Gil Loaiza, J., Buzzard, V., & Meredith, L. (2018, August). Cell Count and Viability Within the Rainwater Supply of the Landscape Evolution Observatory. UROC and AZDM poster presentations. Tucson, AZ.
• Thorne, D., Buzzard, V., Cueva, A., Gil Loaiza, J., Braendholt, A., & Meredith, L. (2018, October). Variability in microbial soil hydrogen fluxes across GI treatment and monsoonal moisture regimes. Research Insights in Semiarid Ecosystems Symposium. Tucson, AZ.
• Troch, P. A., Chorover, J. D., Harman, C., Dontsova, K. M., Meredith, L., Wang, Y., Sengupta, A., Meira Neto, A., Matos, K., Hunt, E., Bugaj, A., Abramson, N., Volkmann, T., Kim, M., Troch, P. A., Chorover, J. D., Harman, C., Dontsova, K. M., Meredith, L., , Wang, Y., et al. (2018, December). H13N-1958 Experimental observation of a hillslope-scale rank StorAge Selection function: Process controls on its functional form, time variability, and hysteresis.. American Geophysical Union fall meeting. Washington, DC: American Geophysical Union.
• Wingate, L., Lanois, T., Cuntz, M., Meredith, L., Sauze, J., & Ogee, J. (2018, April). A novel CO18O dataset and modelling framework to constrain estimates of photosynthesis at the global scale. European Geophysical Union. Vienna, Austria.
• Cueva, A., Volkmann, T. H., Sengupta, A., Troch, P. A., & Meredith, L. (2017, Dec). Linking genes to ecosystem trace gas fluxes in a large-scale model system. AGU International Annual Meeting. New Orleans, LA.
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  Soil microorganisms mediate biogeochemical cycles through biosphere-atmosphere gas exchange with significant impact on atmospheric trace gas composition. Improving process-based understanding of these microbial populations and linking their genomic potential to the ecosystem-scale is a challenge, particularly in soil systems, which are heterogeneous in biodiversity, chemistry, and structure. In oligotrophic systems, such as the Landscape Evolution Observatory (LEO) at Biosphere 2, atmospheric trace gas scavenging may supply critical metabolic needs to microbial communities, thereby promoting tight linkages between microbial genomics and trace gas utilization. This large-scale model system of three initially homogenous and highly instrumented hillslopes facilitates high temporal resolution characterization of subsurface trace gas fluxes at hundreds of sampling points, making LEO an ideal location to study microbe-mediated trace gas fluxes from the gene to ecosystem scales. Specifically, we focus on the metabolism of ubiquitous atmospheric reduced trace gases hydrogen (H2), carbon monoxide (CO), and methane (CH4), which may have wide-reaching impacts on microbial community establishment, survival, and function. Additionally, microbial activity on LEO may facilitate weathering of the basalt matrix, which can be studied with trace gas measurements of carbonyl sulfide (COS/OCS) and carbon dioxide (O-isotopes in CO2), and presents an additional opportunity for gene to ecosystem study. This work will present initial measurements of this suite of trace gases to characterize soil microbial metabolic activity, as well as links between spatial and temporal variability of microbe-mediated trace gas fluxes in LEO and their relation to genomic-based characterization of microbial community structure (phylogenetic amplicons) and genetic potential (metagenomics). Results from the LEO model system will help build understanding of the importance of atmospheric inputs to microorganisms pioneering fresh mineral matrix. Additionally, the measurement and modeling techniques that will be developed at LEO will be relevant for other investigators linking microbial genomics to ecosystem function in more well-developed soils with greater complexity.
• Kaur, R., Sengputa, A., Meredith, L., & Troch, P. A. (2017, Dec). Spatial and temporal heterogeneity of microbial life in artificial landscapes. AGU International Annual Meeting. New Orleans, LA.
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  The Landscape Evolution Observatory (LEO) project at Biosphere 2 consists of three replicated artificial landscapes which are sealed within a climate-controlled glass house. LEO is composed of basaltic soil material with low organic matter, nutrients, and microbes. The landscapes are built to resemble zero-order basins and enable researchers to observe hydrological, biological, and geochemical evolution of landscapes in a controlled environment. This study is focused on capturing microbial community dynamics in LEO soil, pre- and post-controlled rainfall episodes. Soil samples were collected from six different locations and at five depths in each of the three slopes followed by DNA extraction from 180 samples and sent for amplicon and minimal draft metagenome sequencing. The average concentration of DNA recovered from each sample was higher in the post-rainfall samples than the pre-rainfall samples, a trend consistent in all three slopes. The sequence data will be evaluated to reveal heterogeneity of the soil microbes, providing a more exact narrative of the microbes present in each slope and the spatiotemporal trends of microbial life in the landscapes. Next, functional traits will be predicted from the community data and metagenomes to determine whether consistent changes occur with respect to wetting and drying episodes. Together, these results will highlight the relevance of a unique terrestrial ecosystem research infrastructure in supporting interdisciplinary hydrobiogeochemical research.
• Meraz, J. C., Meraz, J. C., Meredith, L., Meredith, L., Van Haren, J. L., Van Haren, J. L., Volkmann, T. H., & Volkmann, T. H. (2017, Dec). Measuring volatile organic compounds and stable isotopes emitted from trees and soils of the Biosphere 2 Rainforest. AGU International Annual Meeting. New Orleans, LA.
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  Rainforest trees and soils play an important role in volatile organic compound (VOC) emissions. It is known that many rainforest tree species emit these organic compounds, such as terpenes, which can have an impact on the atmosphere and can be indicative of their metabolic functions. Some VOCs also absorb infrared radiation at wavelengths at which water isotopes are measured with laser spectrometers. Normal concentrations are not high enough for ambient sampling, but increased concentrations resulting from soil and plant samples extracted using equilibrium methods affect observed isotope ratios. There is thus a need to characterize volatile emissions from soil and plant samples, and to develop better methods to account for VOC interference during water isotope measurements. In this study, we collected soil and leaf samples from plants of the Biosphere 2 Rainforest Biome, a mesocosm system created to stimulate natural tropical rainforest habitats . Volatile concentrations were measured using a Gasmet DX4015 FTIR analyzer and a custom sampling system with sulfur hexafluoride (SF6) used as a tracer gas to test for leakage, and a commercial laser spectrometer was used for isotopic analysis. We determined that the different types of tree species emit different kinds of VOCs, such as isoprenes, alcohols, and aldehydes, that will potentially have to be accounted for. This study will help build the understanding of which organic compounds are emitted and develop new methods to test for water isotopes and gas fluxes in clear and precise measures. Such measures can help characterize the functioning of environmental systems such as the Biosphere 2 Rainforest Biome.
• Meredith, L., Sengupta, A., Troch, P. A., & Volkmann, T. H. (2017, Dec). Noninvasive methods for dynamic mapping of microbial populations across the landscape. AGU International Annual Meeting. New Orleans, LA.
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  Soil microorganisms drive key ecosystem processes, and yet characterizing their distribution and activity in soil has been notoriously difficult. This is due, in part, to the heterogeneous nature of their response to changing environmental and nutrient conditions across time and space. These dynamics are challenging to constrain in both natural and experimental systems because of sampling difficulty and constraints. For example, soil microbial sampling at the Landscape Evolution Observatory (LEO) infrastructure in Biosphere 2 is limited in efforts to minimize soil disruption to the long term experiment that aims to characterize the interacting biological, hydrological, and geochemical processes driving soil evolution. In this and other systems, new methods are needed to monitor soil microbial communities and their genetic potential over time. In this study, we take advantage of the well-defined boundary conditions on hydrological flow at LEO to develop a new method to nondestructively characterize in situ microbial populations. In our approach, we sample microbes from the seepage flow at the base of each of three replicate LEO hillslopes and use hydrological models to ‘map back’ in situ microbial populations. Over the course of a 3-month periodic rainfall experiment we collected samples from the LEO outflow for DNA and extraction and microbial community composition analysis. These data will be used to describe changes in microbial community composition over the course of the experiment. In addition, we will use hydrological flow models to identify the changing source region of discharge water over the course of periodic rainfall pulses, thereby mapping back microbial populations onto their geographic origin in the slope. These predictions of in situ microbial populations will be ground-truthed against those derived from destructive soil sampling at the beginning and end of the rainfall experiment. Our results will show the suitability of this method for long-term, non-destructive monitoring of the microbial communities that contribute to soil evolution in this large-scale model system. Furthermore, this method may be useful for other study systems with limitations to destructive sampling including other model infrastructures and natural landscapes.
• Troch, P. A., Zeng, X., Wang, Y., Van Haren, J. L., Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pelletier, J. D., Niu, G., Monson, R. K., Meredith, L., Alves Meira Neto, A., Matos, K. A., Maier, R. M., Kim, M., Hunt, E. A., , Harman, C. J., et al. (2017, December). Controlled Experiments of Hillslope Co-evolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological change. 2017 AGU Fall Meeting, Abstract B43A-2105. New Orleans, LA: American Geophysical Union (AGU).
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  Understanding the process interactions and feedbacks among water, microbes, plants, and porous geological media is crucial for improving predictions of the response of Earth’s critical zone to future climatic conditions. However, the integrated co-evolution of landscapes under change is notoriously difficult to investigate. Laboratory studies are typically limited in spatial and temporal scale, while field studies lack observational density and control. To bridge the gap between controlled lab and uncontrolled field studies, the University of Arizona – Biosphere 2 built a macrocosm experiment of unprecedented scale: the Landscape Evolution Observatory (LEO). LEO consists of three replicated, 330-m2 hillslope landscapes inside a 5000-m2 environmentally controlled facility. The engineered landscapes contain 1-m depth of basaltic tephra ground to homogenous loamy sand that will undergo physical, chemical, and mineralogical changes over many years. Each landscape contains a dense sensor network capable of resolving water, carbon, and energy cycling processes at sub-meter to whole-landscape scale. Embedded sampling devices allow for quantification of biogeochemical processes, and facilitate the use of chemical tracers applied with the artificial rainfall. LEO is now fully operational and intensive forcing experiments have been launched. While operating the massive infrastructure poses significant challenges, LEO has demonstrated the capacity of tracking multi-scale matter and energy fluxes at a level of detail impossible in field experiments. Initial sensor, sampler, and restricted soil coring data are already providing insights into the tight linkages between water flow, weathering, and (micro-) biological community development during incipient landscape evolution. Over the years to come, these interacting processes are anticipated to drive the model systems to increasingly complex states, potentially perturbed by changes in climatic forcing. By intensively monitoring the evolutionary trajectory, integrating data with models, and fostering community-wide collaborations, we envision that emergent landscape structures and functions can be linked and significant progress can be made toward predicting the coupled hydro-biogeochemical and ecological responses to global change.
• Troch, P. A., Zeng, X., Wang, Y., Van Haren, J. L., Tuller, M., Sibayan, M., Schaap, M. G., Saleska, S. R., Ruiz, J., Rasmussen, C., Pelletier, J. D., Niu, G., Monson, R. K., Meredith, L., Alves Meira Neto, A., Matos, K. A., Maier, R. M., Kim, M., Hunt, E. A., , Harman, C. J., et al. (2017, December). Controlled Experiments of Hillslope Co-evolution at the Biosphere 2 Landscape Evolution Observatory: Toward Prediction of Coupled Hydrological, Biogeochemical, and Ecological change. AGU International Annual Meeting. New Orleans, LA: American Geophysical Union (AGU).
• Webster, K., Meredith, L., Piccini, W., Pedrinho, A., Nüsslein, K., Van Haren, J. L., Barbosa de Camargo, P., Siu Mui, T., & Saleska, S. R. (2017, Dec). Recovery of Methane Consumption by Secondary Forests in the Amazon River Basin. AGU International Annual Meeting. New Orleans, LA.
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  Methane (CH4) is a major greenhouse gas in Earth’s atmosphere and its atmospheric global mole fraction has roughly doubled since the start of the industrial revolution. The tropics are thought to be a major CH4 emitter, with the Amazon River Basin estimated to contribute 7 % of the annual flux to the atmosphere. The Amazon has experienced extensive land use change during the past 30 years, but we lack an understanding of the qualitative and quantitative effects of land use change on CH4 flux from the Amazon and the associated reasons. To illuminate the factors controlling CH4 flux across land use gradients in the Amazon we measured the CH4 fluxes and will measure the associated stable isotopic composition from pastures, primary forests, and secondary forests, at Ariquemes (Western Amazon, more deforested), and Santarem (Eastern Amazon, less deforested), Brazil. The sites near Santarem were sampled in June of 2016 and the sites near Ariquemes were sampled in March and April of 2017, both at the end of the wet season. Little difference was observed between land use types in Santarem with each land use type slightly consuming atmospheric CH4. However, pasture fluxes at Ariquemes were higher (+520 μg-C m-2 hr-1) than in primary (0 μg-C m-2 hr-1) and secondary forests (-20 μg-C m-2 hr-1; p = 6*10-4). CH4 flux from individual Santarem sites was not correlated with environmental variables. CH4 flux from Airquemes was correlated with several parameters across all samples including soil temperature (p = 7*10-4), and soil humidity (p = 0.02). Despite the fact that pastures experienced higher soil temperatures than forest soils this appears to be a low predictor of CH4 flux from these environments as it was seen at both Santarem and Ariquemes. The analysis of the stable isotopic composition of CH4 from these chambers will aid in understanding the competing processes of microbial CH4 consumption and production in these soils and why pastures may become CH4 sources and secondary forests are able to regain the function as a CH4 sink in some instances. Support: NSF, FAPESP-Biota, CNPq, CAPES.
• Young, J. C., Young, J. C., Young, J. C., Meredith, L., Sengupta, A., Sengupta, A., Sengupta, A., Van Haren, J. L., Uren, J. M., Uren, J. M., Uren, J. M., Uren, J. M., Sengupta, A., Van Haren, J. L., Van Haren, J. L., Van Haren, J. L., Young, J. C., Meredith, L., Meredith, L., & Meredith, L. (2017, Dec). Microbial drivers of spatial heterogeneity of nitrous oxide pulse dynamics following drought in an experimental tropical rainforest. AGU International Annual Meeting. New Orleans, LA.
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  Nitrous oxide (N2O) is a long-lived, potent greenhouse gas with increasing atmospheric concentrations. Soil microbes in agricultural and natural ecosystems are the dominant source of N2O, which involves complex interactions between N-cycling microbes, metabolisms, soil properties, and plants. Tropical rainforests are the largest natural source of N2O, however the microbial and environmental drivers are poorly understood as few studies have been performed in these environments. Thus, there is an urgent need for further research to fill in knowledge gaps regarding tropical N-cycling, and the response of soil microbial communities to changes in precipitation patterns, temperature, nitrogen deposition, and land use. To address this data gap, we performed a whole-forest drought in the tropical rainforest biome in Biosphere 2 (B2) and analyzed connections between soil microbes, forest heterogeneity, and N2O emissions. The B2 rainforest is the hottest tropical rainforest on Earth, and is an important model system for studying the response of tropical forests to warming with controlled experimentation. In this study, we measured microbial community abundance and diversity profiles (16S rRNA and ITS2 amplicon sequencing) along with their association with soil properties (e.g. pH, C, N) during the drought and rewetting at five locations (3 depths), including regions that have been previously characterized with high and low N2O drought pulse dynamics (van Haren et al., 2005). In this study, we present the spatial distribution of soil microbial communities within the rainforest at Biosphere 2 and their correlations with edaphic factors. In particular, we focus on microbial, soil, and plant factors that drive high and low N2O pulse zones. As in the past, we found that N2O emissions were highest in response to rewetting in a zone hypothesized to be rich in nutrients from a nearby sugar palm. We will characterize microbial indicator species and nitrogen cycling genes to better resolve N cycling across the forest. Understanding how N2O formation is mediated by soil microbes in response to drought in tropical rainforests is challenging given the great diversity of microbial communities and metabolisms involved, but is critical for understanding the source of global increases in atmospheric N2O.

Others

• Crocker, L. N. (2021, December). The Composition and Diversity of Volatile Organic Compounds (VOCs) from Leaf Litter in the Biosphere 2 Tropical Rainforest. MS Thesis.