Interests

Research

Rangeland Vegetation Dynamics, Rangeland Management

Teaching

Rangeland Plant Communities, Rangeland Management

Courses

Scholarly Contributions

Chapters

• Pulido, F., McCreary, D., Canellas, I., Mcclaran, M. P., & Plieninger, M. (2013). Oak regeneration: ecological dynamics and restoration techniques.. In Mediterranean Oak Woodland Working Landscapes: Dehesas of Spain and Ranchlands of California.(pp 123-144). Springer-Verlag.
• Allen-diaz, B., Bartolome, J. W., & Mcclaran, M. P. (1999).

  California Oak Savanna

  . In Savannas, Barrens, and Rock Outcrop Plant Communities of North America:(pp 322-339). Cambridge University Press. doi:10.1017/CBO9780511574627.021
• Mcclaran, M. P., & Mcpherson, G. R. (1999).

  Oak Savanna in the American Southwest

  . In Savannas, Barrens, and Rock Outcrop Plant Communities of North America:(pp 275-287). Cambridge University Press. doi:10.1017/CBO9780511574627.018
• Mcclaran, M. P., Ang, P. O., Capurro, A., Deutschman, D. H., Shafer, D. J., & Guarini, J. (1995).

  Interpreting Explanatory Processes for Time Series Patterns: Lessons from Three Time Series

  . In Ecological Times Series(pp 465-82). Springer, Boston, MA. doi:10.1007/978-1-4615-1769-6_21
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  What processes are responsible for time series patterns? This is the seminal question for ecologists and a critical question for society’s response to changing environments. Through an historical review of three time series and the processes proposed as explanations for them, we illustrate that process interpretation begins with descriptive analysis of the time series and is clarified by greater time series length, additional time series from other areas, correlation analysis with ancillary data, simulation models, and experimentation.

Journals/Publications

• Eldridge, D., Ding, J., Dorrough, J., Delgado-Baquerizo, M., Sala, O., Gross, N., Le Bagousse-Pinguet, Y., Mallen-Cooper, M., Saiz, H., Asensio, S., Ochoa, V., Gozalo, B., Guirado, E., Valencia, E., Plaza, C., Abedi, M., Ahmadian, N., Ahumada, R., Amghar, F., , Azevedo, L., et al. (2024). Correction to: Hotspots of biogeochemical activity linked to aridity and plant traits across global drylands (Nature Plants, (2024), 10, 5, (760-770), 10.1038/s41477-024-01670-7). Nature Plants, 10(5). doi:10.1038/s41477-024-01708-w
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  Correction to: Nature Plantshttps://doi.org/10.1038/s41477-024-01670-7, published online 12 April 2024 In the version of the article initially published, affiliation 30 was incorrect and has now been updated to Plant Ecology Group, Department of Evolution and Ecology, University of Tübingen, Tübingen, Germany. Additionally, Pierre Liancourt’s second affiliation (State Museum of Natural History Stuttgart, Stuttgart, Germany) was missing and has now been added. These changes have been made to the HTML and PDF versions of the article.
• Eldridge, D., Ding, J., Dorrough, J., Delgado-Baquerizo, M., Sala, O., Gross, N., Le Bagousse-Pinguet, Y., Mallen-Cooper, M., Saiz, H., Asensio, S., Ochoa, V., Gozalo, B., Guirado, E., Valencia, E., Plaza, C., Abedi, M., Ahmadian, N., Ahumada, R., Amghar, F., , Azevedo, L., et al. (2024). Hotspots of biogeochemical activity linked to aridity and plant traits across global drylands. Nature Plants, 10(760-770). doi:10.1038/s41477-024-01670-7
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  Perennial plants create productive and biodiverse hotspots, known as fertile islands, beneath their canopies. These hotspots largely determine the structure and functioning of drylands worldwide. Despite their ubiquity, the factors controlling fertile islands under conditions of contrasting grazing by livestock, the most prevalent land use in drylands, remain virtually unknown. Here we evaluated the relative importance of grazing pressure and herbivore type, climate and plant functional traits on 24 soil physical and chemical attributes that represent proxies of key ecosystem services related to decomposition, soil fertility, and soil and water conservation. To do this, we conducted a standardized global survey of 288 plots at 88 sites in 25 countries worldwide. We show that aridity and plant traits are the major factors associated with the magnitude of plant effects on fertile islands in grazed drylands worldwide. Grazing pressure had little influence on the capacity of plants to support fertile islands. Taller and wider shrubs and grasses supported stronger island effects. Stable and functional soils tended to be linked to species-rich sites with taller plants. Together, our findings dispel the notion that grazing pressure or herbivore type are linked to the formation or intensification of fertile islands in drylands. Rather, our study suggests that changes in aridity, and processes that alter island identity and therefore plant traits, will have marked effects on how perennial plants support and maintain the functioning of drylands in a more arid and grazed world. In global drylands, soils tend to be more fertile beneath tree, shrub and grass islands. Soil fertility was greater beneath taller and wider plants but was unaffected by either grazing pressure or the type of herbivore.
• Maestre, F., Delgado-Baquerizo, M., Eldridge, D., Saiz, H., Gross, N., Le Bagousse-Pinguet, Y., Gozalo, B., Ochoa, V., Guirado, E., Valencia, E., Asensio, S., Berdugo, M., Mendoza, B., Zaccone, C., Panettieri, M., Fan, W., Benavente-Ferraces, I., Rey, A., Eisenhauer, N., , Cesarz, S., et al. (2024). Vulnerability of mineral-associated soil organic carbon to climate across global drylands. Nature Climate Change, 14(9). doi:10.1038/s41558-024-02087-y
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  Mineral-associated organic carbon (MAOC) constitutes a major fraction of global soil carbon and is assumed less sensitive to climate than particulate organic carbon (POC) due to protection by minerals. Despite its importance for long-term carbon storage, the response of MAOC to changing climates in drylands, which cover more than 40% of the global land area, remains unexplored. Here we assess topsoil organic carbon fractions across global drylands using a standardized field survey in 326 plots from 25 countries and 6 continents. We find that soil biogeochemistry explained the majority of variation in both MAOC and POC. Both carbon fractions decreased with increases in mean annual temperature and reductions in precipitation, with MAOC responding similarly to POC. Therefore, our results suggest that ongoing climate warming and aridification may result in unforeseen carbon losses across global drylands, and that the protective role of minerals may not dampen these effects.
• Wilmer, H., Ferguson, D., Dinan, M., Thacker, E., Adler, P., Walsh, K., Bradford, J., Brunson, M., Derner, J., Elias, E., Felton, A., Gray, C., Greene, C., McClaran, M., Shriver, R., Stephenson, M., & Suding, K. (2024). Resilience Is Not Enough: Toward a More Meaningful Rangeland Adaptation Science. Rangeland Ecology and Management, 95. doi:10.1016/j.rama.2024.04.003
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  Rangeland ecosystems, and their managers, face the growing urgency of climate change impacts. Researchers are therefore seeking integrative social-ecological frameworks that can enhance adaptation by managers to these climate change dynamics through tighter linkages among multiple scientific disciplines and manager contexts. Social-ecological framings, including resilience and vulnerability, are popular in such efforts, but their potential to inform meaningful rangeland adaptation science is limited by traditional disciplinary silos. Here, we provide reflective lessons learned from a multidisciplinary Rangelands, Ranching, and Resilience (R3) project on U.S. western rangelands that addressed 1) biophysical science projections of forage production under future climate scenarios, 2) ranchers’ views of resilience using social science methods, and 3) outreach efforts coordinated through extension professionals. Despite the project's initial intentions, human dimensions and ecological researchers largely worked in parallel sub-teams during the project, rather than weaving their expertise together with managers. The R3 project was multidisciplinary, but it provides a case study on lessons learned to suggest how social and ecological researchers can move towards approaches that transcend individual disciplines. Transdisciplinary science and management in rangelands requires more than just conceptual social-ecological frameworks. Additional methodological concepts need to include: 1) relationship building; 2) shared meaning making; and 3) a commitment to continual conversations and learning, or staying with the trouble, following Haraway (2016). If the goal is to address meaningful rangeland adaptation science rather than just produce academic products, researchers, outreach professionals, and rangeland-based communities should address a series of critical troubling questions. In the process of addressing these, deeper engagement among and beyond disciplines will occur as relationship building, shared meaning, and continual conversations and learning facilitate staying with the trouble.
• Liptzin, D., Rieke, E. L., Cappellazzi, S. B., Bean, G. M., Cope, M., Greub, K. L., Norris, C. E., Tracy, P. W., Aberle, E., Ashworth, A., Tavarez, O. B., Bary, A. I., Baumhardt, R. L., Gracia, A. B., Brainard, D. C., Brennan, J. R., Reyes, D. B., Bruhjell, D., Carlyle, C. N., , Crawford, J. J., et al. (2023). An evaluation of nitrogen indicators for soil health in long‐term agricultural experiments. Soil Science Society of America Journal, 87(4), 868-884. doi:10.1002/saj2.20558
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  Abstract Various soil health indicators that measure a chemically defined fraction of nitrogen (N) or a process related to N cycling have been proposed to quantify the potential to supply N to crops, a key soil function. We evaluated five N indicators (total soil N, autoclavable citrate extractable N, water‐extractable organic N, potentially mineralizable N, and N ‐acetyl‐β‐ D ‐glucosaminidase activity) at 124 sites with long‐term experiments across North America evaluating a variety of managements. We found that 59%–81% of the variation in N indicators was among sites, with indicator values decreasing with temperature and increasing with precipitation and clay content. The N indicators increased from 6%–39% in response to decreasing tillage, cover cropping, retaining residue, and applying organic sources of nutrients. Overall, increasing the quantity of organic inputs, whether from increased residue retention, cover cropping, or rotations with higher biomass, resulted in higher values of the N indicators. Although N indicators responded to management in similar ways, the analysis cost and availability of testing laboratories is highly variable. Further, given the strong relationships of the N indicators with carbon (C) indicators, measuring soil organic C along with 24‐h potential C mineralization could be used as a proxy for N supply instead of measuring potentially mineralizable N or any other N indicator directly.
• Liptzin, D., Rieke, E., Cappellazzi, S., Bean, G., Cope, M., Greub, K., Norris, C., Tracy, P., Aberle, E., Ashworth, A., Tavarez, O., Bary, A., Baumhardt, R., Gracia, A., Brainard, D., Brennan, J., Reyes, D., Bruhjell, D., Carlyle, C., , Crawford, J., et al. (2023). An evaluation of nitrogen indicators for soil health in long-term agricultural experiments. Soil Science Society of America Journal, 172, 1-17. doi:10.1002/saj2.20558
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  Various soil health indicators that measure a chemically defined fraction of nitrogen (N) or a process related to N cycling have been proposed to quantify the potential to supply N to crops, a key soil function. We evaluated five N indicators (total soil N, autoclavable citrate extractable N, water-extractable organic N, potentially mineralizable N, and N-acetyl-β-D-glucosaminidase activity) at 124 sites with long-term experiments across North America evaluating a variety of managements. We found that 59%–81% of the variation in N indicators was among sites, with indicator values decreasing with temperature and increasing with precipitation and clay content. The N indicators increased from 6%–39% in response to decreasing tillage, cover cropping, retaining residue, and applying organic sources of nutrients. Overall, increasing the quantity of organic inputs, whether from increased residue retention, cover cropping, or rotations with higher biomass, resulted in higher values of the N indicators. Although N indicators responded to management in similar ways, the analysis cost and availability of testing laboratories is highly variable. Further, given the strong relationships of the N indicators with carbon (C) indicators, measuring soil organic C along with 24-h potential C mineralization could be used as a proxy for N supply instead of measuring potentially mineralizable N or any other N indicator directly.
• Ponce‐Campos, G. E., McClaran, M. P., Heilman, P., & Gillan, J. K. (2023). UAV and Satellite-Based Sensing to Map Ecological States at the Landscape Scale. Open Journal of Ecology, 13, 560-596. doi:10.4236/oje.2023.138035
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  Mapping ecological states in semi-arid rangelands is crucial for effective land management and conservation efforts because it identifies difference in the ecological conditions across a landscape. This study presents an innovative approach for mapping two ecological states, Large Shrub Grass (LSG) and Large Shrub Eroded (LSE), within the Sandy Loam Upland and Deep (SLUD) ecological sites using a combination of drone and satellite data. The methodology leverages the Largest Patch Index (LPI) as a proxy metric to estimate eroded areas and classify ecological states. The integration of unmanned aerial vehicle (UAV) data with satellite-based remote sensing provides a scalable approach that can benefit various stakeholders involved in rangeland management. The study demonstrates the potential of this methodology by generating spatial layers at the landscape scale to inform on the state of rangeland ecosystems. The workflow showcases the power of remote sensing technology to map ecological states and addresses limitations in spatial coverage by integrating UAV and satellite data. By utilizing the bare ground LPI metric, which indicates the connectedness of bare ground, the methodology enables the classification of ecological states at a regional scale. This cost-effective approach potentially offers a standardized and reproducible method applicable across different sites and regions. The accuracy of the classification process is evaluated by comparing the results to ground-based polygons, dirt roads, and water locations. While the model performs well in identifying eroded areas, misclassifications occur in regions with mixed vegetation cover or low biomass. Future research should focus on incorporating temporal information from historical remote sensing archives to improve understanding of ecological state dynamics. Additionally, validation efforts can be enhanced by incorporating more ground-truth data and testing the methodology in diverse rangeland areas. The workflow serves as a blueprint for scaling up ecological states mapping in similar semi-arid rangelands. Further work should involve refining the approach through additional validation and exploring new remote sensing datasets. The methodology can be replicated in other regions to inform land management decisions, promote sustainable resource use, and advance the field of ecological states mapping.
• Rieke, E., Many, O., Mcclaran, M. P., & Many, O. (2022). Linking microbial community structure to potential carbon mineralization: A continental scale assessment. Soil Biology and Biochemistry, 168, 108618. doi:https://doi.org/10.1016/j.soilbio.2022.108618
• Aberle, E., Alcalá, L. O., Ashworth, A., Bagnall, D. K., Bary, A. I., Baumhardt, R. L., Bean, G. M., Brainard, D. C., Brennan, J. R., Bruhjell, D., Campos, A. T., Cappellazzi, S. B., Carlyle, C. N., Cope, M., Crawford, J. J., Creech, C. F., Culman, S. W., Deen, B., Dell, C. J., , Derner, J. D., et al. (2022). Selecting soil hydraulic properties as indicators of soil health: Measurement response to management and site characteristics. Soil Science Society of America Journal, 86(5), 1206-1226. doi:10.1002/saj2.20428
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  Abstract Farmers, scientists, and other soil health stakeholders require interpretable indicators of soil hydraulic function. Determining which indicators to use has been difficult because of measurement disconformity, spatial and temporal variability, recently established treatments, and the effect of site characteristics on management practice differences. The North American Project to Evaluate Soil Health Measurements includes 124 sites uniformly sampled across a range of soil health management practices in North America in 2019. We compare and recommend indicators of hydraulic function that best characterize soil health. We assessed the relationship of each indicator to a suite of soil inherent properties and climate variables, the response of each indicator to soil health management practices, the effect that soil inherent properties (clay content, sand content, and pH) and climatic variables (10‐yr mean annual precipitation and temperature) had on response to management practices, and the relationship among the responses of the indicators to soil health management practices. Field capacity measured on intact cores (θ FC_INTACT ) was the best measure of soil hydraulic function, because it responded to management, represents a direct measure of soil hydraulic function, is proximal to stakeholder values, and its response to management was not significantly influenced by inherent and climatic variables. Other suitable indicators are bulk density, soil organic carbon (SOC), and aggregate stability, which are not direct measures of soil hydraulic function but do respond to management and may be practical in situations in which measuring θ FC_INTACT is not. This study informs selection of soil health indicators to measure soil hydraulic function.
• Aberle, E., Alcalá, L. O., Ashworth, A., Bagnall, D. K., Bary, A., Baumhardt, R. L., Bean, G. M., Brainard, D. C., Brennan, J. R., Bruhjell, D., Cappellazzi, S. B., Carlyle, C. N., Cope, M., Crawford, J. J., Creech, C. F., Culman, S. W., Deen, B., Dell, C. J., Derner, J. D., , Ducey, T. F., et al. (2022).

  Evaluation of Aggregate Stability Methods for Soil Health

  . Social Science Research Network. doi:10.2139/ssrn.4129844
• Anselmetto, N., Gorlier, A., McClaran, M. P., & Nota, G. (2022).

  Differences in population size structures characterize grass response to long‐term livestock removal

  . Applied Vegetation Science, 25(4). doi:10.1111/avsc.12696
• Bagnall, D., Many, O., Mcclaran, M. P., & Many, O. (2022). Carbon-sensitive pedotransfer functions for plant available water. . Soil Science Society of America Journal, 86, 612-629. doi:https://doi.org/10.1002/saj2.20395
• Bagnall, D., Morgan, C., Bean, G., Liptzin, D., Cappellazzi, S., Cope, M., Greub, K., Rieke, E., Norris, C., Tracy, P., Aberle, E., Ashworth, A., Tavarez, O., Bary, A., Baumhardt, R., Gracia, A., Brainard, D., Brennan, J., Reyes, D., , Bruhjell, D., et al. (2022). Selecting soil hydraulic properties as indicators of soil health: Measurement response to management and site characteristics. Soil Science Society of America Journal, 86(5). doi:10.1002/saj2.20428
  More info

  Farmers, scientists, and other soil health stakeholders require interpretable indicators of soil hydraulic function. Determining which indicators to use has been difficult because of measurement disconformity, spatial and temporal variability, recently established treatments, and the effect of site characteristics on management practice differences. The North American Project to Evaluate Soil Health Measurements includes 124 sites uniformly sampled across a range of soil health management practices in North America in 2019. We compare and recommend indicators of hydraulic function that best characterize soil health. We assessed the relationship of each indicator to a suite of soil inherent properties and climate variables, the response of each indicator to soil health management practices, the effect that soil inherent properties (clay content, sand content, and pH) and climatic variables (10-yr mean annual precipitation and temperature) had on response to management practices, and the relationship among the responses of the indicators to soil health management practices. Field capacity measured on intact cores (θFC_INTACT) was the best measure of soil hydraulic function, because it responded to management, represents a direct measure of soil hydraulic function, is proximal to stakeholder values, and its response to management was not significantly influenced by inherent and climatic variables. Other suitable indicators are bulk density, soil organic carbon (SOC), and aggregate stability, which are not direct measures of soil hydraulic function but do respond to management and may be practical in situations in which measuring θFC_INTACT is not. This study informs selection of soil health indicators to measure soil hydraulic function.
• Crimmins, M. A., Brischke, A. S., Hall, A. L., & Mcclaran, M. P. (2022). Ranch-scale Drought Monitoring Tools for Arizona. University of Arizona Cooperative Extension Bulletin.
• Greene, C., Wilmer, H., Ferguson, D. B., Crimmins, M. A., & Mcclaran, M. P. (2022). Rancher’s Knowledge of Social-Ecological Change: Centering Agency and Scale in Resilience. . Journal of Rural Studies, 96, 217-226.
• Liptzin, D., Norris, C. E., Cappellazzi, S. B., Bean, G. M., Cope, M., Greub, K. L., Rieke, E. L., Tracy, P. W., Aberle, E., Ashworth, A. J., Tavarez, O. B., Bary, A. I., Baumhardt, R. L., Gracia, A. B., Brainard, D. C., Brennan, J. R., Reyes, D. B., Bruhjell, D., Carlyle, C. N., , Crawford, J. J., et al. (2022). An evaluation of carbon indicators of soil health in long-term agricultural experiments. Soil Biology and Biochemistry, 172, 108708. doi:10.1016/j.soilbio.2022.108708
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  Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and β-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confidence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.
• Liptzin, D., Norris, C., Cappellazzi, S., Bean, G., Cope, M., Greub, K., Rieke, E., Tracy, P., Aberle, E., Ashworth, A., Bary, A., Baumhardt, R., Brainard, D., Brennan, J., Briones Reyes, D., Bruhjell, D., Carlyle, C., Crawford, J., Creech, C., , Culman, S., et al. (2022).

  An evaluation of carbon indicators of soil health in long-term agricultural experiments

  . Soil Science Society of America, 172, 1-17. doi:10.1016/j.soilbio.2022.108708
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  Soil organic carbon (SOC) is closely tied to soil health. However, additional biological indicators may also provide insight about C dynamics and microbial activity. We used SOC and the other C indicators (potential C mineralization, permanganate oxidizable C, water extractable organic C, and β-glucosidase enzyme activity) from the North American Project to Evaluate Soil Health Measurements to examine the continental-scale drivers of these indicators, the relationships among indicators, and the effects of soil health practices on indicator values. All indicators had greater values at cooler temperatures, and most were greater with increased precipitation and clay content. The indicators were strongly correlated with each other at the site-level, with the strongest relationship between SOC and permanganate oxidizable C. The indicator values responded positively to decreased tillage, inclusion of cover crops, application of organic nutrients, and retention of crop residue, but not the number of harvested crops in a rotation. The effect of decreased tillage on the C indicators was generally greater at sites with higher precipitation. The magnitude and direction of the response to soil health practices was consistent across indicators within a site but measuring at least two indicators would provide additional confidence of the effects of management, especially for tillage. All C indicators responded to management, an essential criterion for evaluating soil health. Balancing the cost, sensitivity, interpretability, and availability at commercial labs, a 24-hr potential C mineralization assay could deliver the most benefit to measure in conjunction with SOC.
• Nota, G., Anselmetto, N., Gorlier, A., & Mcclaran, M. P. (2022). Differences in population size structures drive grass response to long-term livestock removal. . Applied Vegetation Science, 2022, 25:e12696.
• Rieke, E. L., Bagnall, D. K., Morgan, C., Flynn, K. D., Howe, J. A., Greub, K. L., Bean, G. M., Cappellazzi, S. B., Cope, M., Liptzin, D., Norris, C. E., Tracy, P. W., Aberle, E., Ashworth, A. J., Tavarez, O. B., Bary, A. I., Baumhardt, R. L., Gracia, A. B., Brainard, D. C., , Brennan, J. R., et al. (2022). Evaluation of aggregate stability methods for soil health. Geoderma, 428, 116156. doi:10.1016/j.geoderma.2022.116156
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  Aggregate stability is a commonly used indicator of soil health because improvements in aggregate stability are related to reduced erodibility and improved soil–water dynamics. During the past 80 to 90 years, numerous methods have been developed to assess aggregate stability. Limited comparisons among the methods have resulted in varied magnitudes of response to soil health management practices and varied influences of inherent soil properties and climate. It is not clear whether selection of a specific method creates any advantage to the investigator. This study assessed four commonly used methods of measuring aggregate stability using data collected as part of the North American Project to Evaluate Soil Health Measurements. The methods included water stable aggregates using the Cornell Rainfall Simulator (WSACASH), wet sieved water stable aggregates (WSAARS), slaking captured and adapted from SLAKES smart-phone image recognition software (STAB10), and the mean weight diameter of water stable aggregates (MWD). Influence of climate and inherent soil properties at the continental scale were analyzed in addition to method responses to rotation diversity, cash crop count, residue management, organic nutrient amendments, cover crops, and tillage. The four methods were moderately correlated with each other. All methods were sensitive to differences in climate and inherent soil properties between sites, although to different degrees. None measured significant effects from rotation diversity or crop count, but all methods detected significant increases in aggregate stability resulting from reduced tillage. Significant increases or positive trends were observed for all methods in relation to cover cropping, increased residue retention, and organic amendments, except for STAB10, which expressed a slightly negative response to organic amendments. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Therefore, secondary considerations (e.g., cost, method availability, increased sensitivity to a specific management practice, or minimal within-treatment variability) driven by the needs of the investigator, should determine the most suitable method.
• Rieke, E. L., Cappellazzi, S. B., Cope, M., Liptzin, D., Bean, G. M., Greub, K. L., Norris, C. E., Tracy, P. W., Aberle, E., Ashworth, A. J., Tavarez, O. B., Bary, A. I., Baumhardt, R. L., Gracia, A. B., Brainard, D. C., Brennan, J. R., Reyes, D. B., Bruhjell, D., Carlyle, C. N., , Crawford, J. J., et al. (2022). Linking soil microbial community structure to potential carbon mineralization: A continental scale assessment of reduced tillage. Soil Biology and Biochemistry, 168, 108618. doi:10.1016/j.soilbio.2022.108618
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  Potential carbon mineralization (Cmin) is a commonly used indicator of soil health, with greater Cmin values interpreted as healthier soil. While Cmin values are typically greater in agricultural soils managed with minimal physical disturbance, the mechanisms driving the increases remain poorly understood. This study assessed bacterial and archaeal community structure and potential microbial drivers of Cmin in soils maintained under various degrees of physical disturbance. Potential carbon mineralization, 16S rRNA sequences, and soil characterization data were collected as part of the North American Project to Evaluate Soil Health Measurements (NAPESHM). Results showed that type of cropping system, intensity of physical disturbance, and soil pH influenced microbial sensitivity to physical disturbance. Furthermore, 28% of amplicon sequence variants (ASVs), which were important in modeling Cmin, were enriched under soils managed with minimal physical disturbance. Sequences identified as enriched under minimal disturbance and important for modeling Cmin, were linked to organisms which could produce extracellular polymeric substances and contained metabolic strategies suited for tolerating environmental stressors. Understanding how physical disturbance shapes microbial communities across climates and inherent soil properties and drives changes in Cmin provides the context necessary to evaluate management impacts on standardized measures of soil microbial activity.
• Rieke, E., Many, O., Mcclaran, M. P., & Many, O. (2022). Evaluation of Aggregate Stability Methods for Soil Health.. Geoderma, 428, 116156. doi:https://doi.org/10.1016/j.geoderma.2022.116156
• Derner, J. D., Haigh, T., Harmoney, K. R., Mcclaran, M. P., Meehan, M. A., Mosley, J. C., Scasta, J. D., Sedivec, K. K., Smart, A. J., Stephenson, M. B., Vermeire, L. T., & Volesky, J. D. (2021).

  Forum: Critical Decision Dates for Drought Management in Central and Northern Great Plains Rangelands

  . Rangeland Ecology & Management, 78, 191-200. doi:10.1016/j.rama.2019.09.005
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  Abstract Ranchers and other land managers of central and northern Great Plains rangelands face recurrent droughts that negatively influence economic returns and environmental resources for ranching enterprises. Accurately estimating annual forage production and initiating drought decision-making actions proactively early in the growing season are both critical to minimize financial losses and degradation to rangeland soil and plant resources. Long-term forage production data sets from Alberta, Kansas, Montana, Nebraska, North Dakota, South Dakota, and Wyoming demonstrated that precipitation in April, May, and June (or some combination of these months) robustly predict annual forage production. Growth curves from clipping experiments and ecological site descriptions (ESDs) indicate that maximum monthly forage growth rates occur 1 mo after the best spring month (April to June) precipitation prediction variable. Key for rangeland managers is that the probability of receiving sufficient precipitation after 1 July to compensate for earlier spring precipitation deficits is extremely low. The complexity of human dimensions of drought decision-making necessitates that forage prediction tools account for uncertainty in matching animal demand to forage availability, and that continued advancements in remote sensing applications address both spatial and temporal relationships in forage production to inform critical decision dates for drought management in these rangeland ecosystems.
• Ganjurjav, H., Gornish, E. S., Liang, M., McClaran, M. P., & Simonis, J. L. (2021).

  Identifying restoration opportunities beneath native mesquite canopies

  . Restoration Ecology, 29(2). doi:10.1111/rec.13334
• Gillan, J. K., Gorlier, A., Heilman, P., McClaran, M. P., Ponce‐Campos, G. E., & Swetnam, T. L. (2021).

  Innovations to expand drone data collection and analysis for rangeland monitoring

  . Ecosphere, 12(7). doi:10.1002/ecs2.3649
• Gillan, J., Ponce Campos, G., Swetnam, T., Gorlier, A., Heilman, P., & Mcclaran, M. P. (2021). Innovations to expand drone data collection and analysis for rangeland monitoring.. Ecosphere, 12(7), e03649.
• Gornish, E., Ganjurjav, H., Liang, M., Simonis, J., & Mcclaran, M. P. (2021). Identifying restoration opportunities beneath native mesquite canopies. Restoration Ecology.
• Hornslein, N., McClaran, M. P., Munson, S., & Throop, H. L. (2021).

  Shrub influence on soil carbon and nitrogen in a semi-arid grassland is mediated by precipitation and largely insensitive to livestock grazing

  . Arid Land Research and Management, 36(1), 27-46. doi:10.1080/15324982.2021.1952660
• Smart, S., Harmoney, K., Scasta, J., Stephenson, M., Volesky, J., Vermiere, L., Mosely, J., Sedivec, K., Meehan, M., Haigh, T., Derner, J., & Mcclaran, M. P. (2021). Critical decision dates for drought management in Central and Northern Great Plains Rangelands. Rangeland Ecology and Management.
• Throoop, H., Munson, S., Hornslein, N., & Mcclaran, M. P. (2021). Shrub influence on soil carbon and nitrogen in a semi-arid grassland is mediated by precipitation and largely insensitive to livestock grazing. Arid Land Research and Management, https://doi.org/10.1080/15324982.2021.1952660.
• Archer, S. R., McClaran, M. P., & Throop, H. L. (2020).

  Soil organic carbon in drylands: shrub encroachment and vegetation management effects dwarf those of livestock grazing

  . Ecological Applications, 30(7). doi:10.1002/eap.2150
• Baccei, J. S., McClaran, M. P., Kuhn, T. J., & Hart, S. C. (2020). Multi-scale drivers of soil resistance predict vulnerability of seasonally wet meadows to trampling by pack stock animals in the Sierra Nevada, USA. Ecological Processes, 9, 32. doi:10.1186/s13717-020-00236-7
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  Abstract Background Meadow ecosystems have important ecological functions and support socioeconomic services, yet are subject to multiple stressors that can lead to rapid degradation. In the Sierra Nevada of the western USA, recreational pack stock (horses and mules) use in seasonally wet mountain meadows may lead to soil trampling and meadow degradation, especially when soil water content is high and vegetation is developing. Methods In order to improve the ability to predict meadow vulnerability to soil disturbance from pack stock use, we measured soil resistance (SR), which is an index of vulnerability to trampling disturbance, at two spatial scales using a stratified-random sampling design. We then compared SR to several soil and vegetation explanatory variables that were also measured at the two spatial scales: plant community type (local scale) and topographic gradient class (meadow scale). Results We found that local-scale differences in drivers of SR were contingent on the meadow scale, which is important because multiple spatial scale evaluation of ecological metrics provides a broader understanding of the potential controls on ecological processes than assessments conducted at a single spatial scale. We also found two contrasting explanatory models for drivers of SR at the local scale: (1) soil gravimetric water content effects on soil disaggregation and (2) soil bulk density and root mass influence on soil cohesion. Soil resistance was insufficient to sustain pack stock use without incurring soil deformation in wet plant communities, even when plant cover was maximal during a major drought. Conclusions Our study provides new information on seasonally wet meadow vulnerability to trampling by pack stock animals using multi-scale drivers of SR, including the contrasting roles of soil disaggregation, friction, and cohesion. Our work aims to inform meadow management efforts in the Sierra Nevada and herbaceous ecosystems in similar regions that are subject to seasonal soil saturation and livestock use.
• Baccei, J. S., Mcclaran, M. P., Kuhn, T. J., & Hart, S. C. (2020). Multi-scale drivers of soil resistance predict vulnerability of seasonally wet meadows to trampling in the Sierra Nevada, USA.. Ecological Processes, 9, 32.
• Brugger, J., McClaran, M., & Sprinkle, J. (2020). ‘Storytelling’ Natural Resource Conflict on U.S. Public Lands. Ethnos, 85(1). doi:10.1080/00141844.2018.1456476
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  Livestock grazing is an extensive and long-standing natural resource use on U.S. public lands that has become extremely controversial in recent decades. In this article, we approach the controversy over public lands grazing as an ‘ontological conflict’ that goes beyond a struggle over different perspectives on nature/reality and involves the ongoing making of different realities/worlds. We bring together historical and ethnographic material from the Tonto National Forest in Arizona in a verbal and visual process of ‘storytelling’ to show how multiple and conflicting imaginations of the public rangelands have emerged and taken on or lost reality over time through multiple, shifting, and often contradictory processes of translation of the relationships among entities in a network that includes humans, nonhumans, discursive and social structures, and social forces. While this approach was originally developed in the context of indigenous studies, it has much to offer in the study of non-indigenous resource conflicts.
• Kariuki, S., Gallery, R. E., Sparks, J., Gimblett, H. R., & Mcclaran, M. P. (2020). Soil microbial activity is resistant to recreational camping disturbance in a Prosopis dominated semiarid savanna.. Applied Soil Ecology.
• Mcclaran, M. P., Archer, S. R., & Throop, H. L. (2020). Soil organic carbon in drylands: shrub encroachment and vegetation management effects dwarf those of livestock grazing. Ecological Applications, 30(7), e02150. doi:doi.org/10.1002/eap.2150
• Noelle, S. M., Lyons, T., Gorlier, A., McClaran, M. P., Nichols, M., & Ruyle, G. B. (2020). How Long Before a Second Defoliation of Actively Growing Grass Plants in the Desert Grassland?. Frontiers in Veterinary Science, 7, 600734. doi:10.3389/fvets.2020.600734
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  In the Desert Grassland, second and subsequent defoliations on perennial grasses during the active growing season can have substantial impacts on grass recovery and reproduction following herbivory. Land managers implement tactics to avoid multiple defoliations on plants by way of rotational grazing, reduced stocking rates, and/or reduced time spent within a given pasture. We explored frequency and rate of defoliation by cattle on perennial bunchgrasses within an 11-day grazing period in three pastures including distance to water (300 and 600 m) and plant height to determine their influence on animal diet selection. Results indicate that 32% of all marked plants were defoliated by cattle and only 5% of defoliated plants were defoliated a second time by day 10 of the grazing period. Defoliation patterns in the studied pastures did not differ between two distances from water, or in relation to plant height. However, at the second defoliation cattle grazed plants that were shorter than at the first defoliation suggesting a selection for high quality re-growth over larger forage on offer. The results of this study show that a 10-day grazing period during the growing season of the Desert Grassland is an effective strategy to avoid second defoliations on individual perennial grass plants while maintaining sufficient forage for use during the dormant winter grazing season.
• Noelle, S., Lyons, T., Gorlier, A., Mcclaran, M. P., Nichols, M., & Ruyle, G. B. (2020). How long before a second defoliation of actively growing grass plants in the Desert Grassland?. Frontiers in Veterinary Science, section Animal Behavior and Welfare.
• Sprinkle, J. E., Brugger, J., Mcclaran, M. P., & Sprinkle, J. E. (2020).

  ‘Storytelling’ Natural Resource Conflict on U.S. Public Lands

  . Ethnos, 85(1), 54-78. doi:10.1080/00141844.2018.1456476
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  Livestock grazing is an extensive and long-standing natural resource use on U.S. public lands that has become extremely controversial in recent decades. In this article, we approach the controversy...
• Throop, H. L., Archer, S. R., & McClaran, M. P. (2020). Soil Organic Carbon in Drylands: Shrub Encroachment and Vegetation Management Effects Dwarf Those of Livestock Grazing. Ecological Applications, 30(7), 2020. doi:10.1002/bes2.1727
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  Shrubs have increased in dryland ecosystems globally over the past century. This land cover change has occurred at the Santa Rita Experimental Range (southern Arizona, USA) in conjunction with well-documented, long-term land management experiments. We contrasted soil organic carbon and nitrogen pools for live shrubs and skeletons on a grazed area and within an exclosure protected from livestock for >100 yr. Improved understanding of how soil biogeochemical pools vary through space, time, and with land use will refine predictions of dryland responses to land use/land cover change, while improving carbon-based management decisions and the evaluation of trade-offs with other ecosystem services. These photographs illustrate the article “Soil organic carbon in drylands: shrub encroachment and vegetation management effects dwarf those of livestock grazing” by Throop, H.L., S.R. Archer, and M.P. McClaran published in Ecological Applications. https://doi.org/10.1002/eap.2150
• Throop, H. L., Mcclaran, M. P., Archer, S. R., Archer, S. R., Throop, H. L., & Mcclaran, M. P. (2020). Photo Gallery: Soil organic carbon in drylands: shrub encroachment and vegetation management effects dwarf those of livestock grazing. Bulletin of the Ecological Society of America, 101(3). doi:doi.org/10.1002/bes2.1727
• Brugger, J., Mcclaran, M. P., & Sprinkle, J. (2019). Story-telling natural resource conflict on U.S. public lands.. Ethnos: Journal of Anthropology, 85(1), 54-78. doi:1080/00141844.2018.1456476
• Gillan, J. K., McClaran, M. P., Swetnam, T. L., & Heilman, P. (2019). Estimating Forage Utilization with Drone-Based Photogrammetric Point Clouds. Rangeland Ecology and Management, 72, 575-585. doi:10.1016/j.rama.2019.02.009
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  Monitoring of forage utilization typically occurs at sample locations, or key areas, selected for their presumed potential to represent utilization across pastures. However, utilization can vary greatly across landscapes and may not be well represented by traditional ground-based sampling without great effort. Remote sensing from satellite and manned airborne platforms offers spatial coverage at landscape scale, but their poor spatial resolution (satellite) and cost (manned airborne) may limit their use in monitoring forage utilization. High-resolution photogrammetric point clouds obtained from small unmanned aerial systems (sUAS) represent an appealing alternative. We developed a method to estimate utilization by observing the height reduction of herbaceous plants represented by 3-dimensional point clouds. We tested our method in a semiarid savanna in southern Arizona by comparing utilization estimates with ground-based methods after a month-long grazing duration. In six plots, we found strong correlation between imagery and ground-based estimates (r2 = 0.78) and similar average estimate of utilization of across all plots (ground-based = 18%, imagery = 20%). With a few workflow and technological improvements, we think it is feasible to estimate point cloud utilization over the entire pasture (150 ha) and potentially even larger areas. These improvements include optimizing the number of images collected and used, equipping drones with more accurate global navigation satellite systems (e.g., Global Positioning System), and processing images with cloud-based parallel processing. We show proof of concept to provide confident estimates of forage utilization patterns over large pastures and landscapes, at levels of spatial precision that are consistent with ground-based methods. The adoption of drone-based monitoring of utilization of forage on rangelands could follow the paradigm shift already demonstrated by Global Positioning Systems and Geographic information systems technologies, where the initial high computing costs were reduced, use became the norm, and the availability of more precise spatial patterns was applied to prescribe and evaluate management practices.
• Gillan, J., Mcclaran, M. P., Swetnam, T. L., & Heilman, P. (2019). Estimating forage utilization with drone-based photogrammetric point clouds. Rangeland Ecology and Management, 72, 575-585.
• Weston, J. D., McClaran, M. P., Whittle, R. K., Black, C. W., & Fehmi, J. S. (2019). Satellite patches, patch expansion, and doubling time as decision metrics for invasion control:Pennisetum ciliareexpansion in southwestern Arizona. Invasive Plant Science and Management, 12, 36-42. doi:10.1017/inp.2019.3
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  Abstract Essential variables to consider for an efficient control strategy for invasive plants include dispersion pattern (i.e., satellite or invasion front) and patch expansion rate. These variables were demonstrated for buffelgrass [ Pennisetum ciliare (L.) Link], a C 4 perennial grass introduced from Africa, which has invaded broadly around the world. The study site was along a roadway in southern Arizona (USA). The P. ciliare plant distributions show the pattern of clumping associated with the satellite (nascent foci) colonization pattern (average nearest neighbor test, z -score −47.2, P
• Weston, J., Mcclaran, M. P., Whittle, R., Black, C. W., & Fehmi, J. S. (2019). Satellite Patches, Patch Expansion, and Doubling Time as Decision Metrics for Invasion Control: Pennisetum ciliare Expansion in Southwestern Arizona. Invasive Plant Science and Management, 12, 36-42.
• Archer, S. R., Huang, C., Marsh, S. E., & McClaran, M. P. (2018).

  Shrub encroachment into grasslands: end of an era?

  . PeerJ, 6, e5474. doi:10.7717/peerj.5474
• Brugger, J., Hawkes, K. L., Bowen, A. M., & Mcclaran, M. P. (2018). Framework for a collaborative process to increase preparation for drought on U.S. public rangelands.. Ecology and Society, 23(4), 18.
• Choy-ing, H., Archer, S. R., Mcclaran, M. P., & Marsh, S. E. (2018). Shrub encroachment into grasslands: end of an era?. PeerJ, 6. doi:10.7717/peerj.5474.
• Hawkes, K., Mcclaran, M. P., Brugger, J., Crimmins, M. A., Howery, L. D., Ruyle, G. B., Sprinkle, J., & Tolleson, D. (2018). Guide to Co-Developing Drought Preparation Plans for Livestock on Southwest National Forests. University of Arizona Cooperartive Extension Bullletin, az1764, 80.
• Swetnam, T., Gillan, J., Sankey, T., Mcclaran, M. P., Nichols, M., Heilman, P., & McVay, J. (2018). Considerations for achieving cross-platform point cloud data fusion across different dryland ecosystem structural states. Frontiers in Plant Science, 8, 13. doi:10.3389/fpls.2017.02144
• Tolleson, D., Sprinkle, J., Ruyle, G. B., Howery, L. D., Crimmins, M. A., Mcclaran, M. P., Brugger, J., & Hawkes, K. (2018). Guide to Co-Developing Drought Preparation Plans for Livestock Grazing on Southwest National Forests. Peer-Reviewed Arizona Cooperative Extension Publication (az1764), 80.
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  Hawkes, K., M. McClaran, J. Brugger, M, Crimmins, L. Howery, G. Ruyle, J. Sprinkle, and D. Tolleson. 2018. Co-Developing Drought Preparation Plans for Livestock Grazing on Southwest National Forests. Peer-Reviewed Arizona Cooperative Extension Publication (az1764).
• Tolleson, D., Sprinkle, J., Ruyle, G. B., Howery, L. D., Crimmins, M. A., Mcclaran, M. P., Brugger, J., & Hawkes, K. (2018). Guide to Co-Developing Drought Preparation Plans for Livestock Grazing on Southwest National Forests. University of Arizona Cooperative Extension Bulletin, 80.
• Bagchi, S., Bestelmeyer, B. T., Briske, D. D., McClaran, M. P., Murthy, K., & Singh, N. J. (2017).

  Quantifying long‐term plant community dynamics with movement models: implications for ecological resilience

  . Ecological Applications, 27(5), 1514-1528. doi:10.1002/eap.1544
• Baghi, S., Singh, N., Briske, D. D., Bestelmeyer, B., Mcclaran, M. P., & Murty, K. (2017). Quantifying long-term trajectories of plant community change with movement models: implication for ecological resilience.. Ecological Applications, 27, 1514-1528.
• Brischke, A. S., Tolleson, D., Hall, A. L., Brugger, J., Mcclaran, M. P., & Crimmins, M. A. (2017). Rain Gauges for Range Management: Precipitation Monitoring Best Practices Guide. University of Arizona Cooperative Extension Publication, 7.
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  Precipitation in the form of rain and snow is critical to many aspects of working lands from controlling the growth of vegetation used in grazing by livestock and wildlife to recharging local water resources found in springs, tanks and riparian areas. Land management decisions often require some knowledge of how much precipitation fell within a management unit to assess how past actions have performed and what to do next. For example, do forage conditions reflect a lack of precipitation or grazing management? Did the next pasture or allotment in my rotation get any rainfall over the past season?
• Crimmins, M. A., Mcclaran, M. P., Brugger, J., Hall, A. L., Tolleson, D., & Brischke, A. S. (2017). Rain Gauges for Range Management: Precipitation Monitoring Best Practices Guide. University of Arizona Cooperative Extension Fast Track.
• Crimmins, M. A., Mcclaran, M. P., Hall, A. L., Brugger, J., & Tolleson, D. (2017). Do-it-yourself Construction Guide: Rugged Accumulation Precipitation Gauge for Remote Monitoring. University of Arizona Cooperative Extension Fast Track.
• Heilman, P., Mcclaran, M. P., Mcvay, J., Nichols, M. H., Sankey, T. T., & Swetnam, T. L. (2017).

  UAV hyperspectral and lidar data and their fusion for arid and semi-arid land vegetation monitoring

  . Remote Sensing in Ecology and Conservation, 4(1), 20-33. doi:10.1002/rse2.44
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  Unmanned aerial vehicles (UAVs) provide a new research tool to obtain high spatial and temporal resolution imagery at a reduced cost. Rapid advances in miniature sensor technology are leading to greater potentials for ecological research. We demonstrate one of the first applications of UAV lidar and hyperspectral imagery and a fusion method for individual plant species identification and 3D characterization at submeter scales in south-eastern Arizona, USA. The UAV lidar scanner characterized the individual vegetation canopy structure and bare ground elevation, whereas the hyperspectral sensor provided species-specific spectral signatures for the dominant and target species at our study area in leaf-on condition. We hypothesized that the fusion of the two different data sources would perform better than either data type alone in the arid and semi-arid ecosystems with sparse vegetation. The fusion approach provides 84–89% overall accuracy (kappa values of 0.80–0.86) in target species classification at the canopy scale, leveraging a wide range of target spectral responses in the hyperspectral data and a high point density (50 points/m2) in the lidar data. In comparison, the hyperspectral image classification alone produced 72–76% overall accuracies (kappa values of 0.70 and 0.71). The UAV lidar-derived digital elevation model (DEM) is also strongly correlated with manned airborne lidar-derived DEM (R2 = 0.98 and 0.96), but was obtained at a lower cost. The lidar and hyperspectral data as well as the fusion method demonstrated here can be widely applied across a gradient of vegetation and topography to monitor and detect ecological changes at a local scale.
• Mcclaran, M. P., Sankey, T., McVay, J., Swetnam, T., Heilman, P., & Nichols, M. (2017). Hyperspectral and lidar data fusion for arid and semi-arid land vegetation monitoring.. Remote Sensing in Ecology and Conservation, 44. doi:doi: 10.1002/rse2.44.
• Brugger, J., & Mcclaran, M. P. (2016). Ranchers, Forest Service, and University of Arizona are co-developing approaches to improve planning for drought on public lands, Part II. DroughtScape: National Drought Mitigation Center Newsletter.
• Brugger, J., Crimmins, M. A., & Mcclaran, M. P. (2016). Groups co-develop approaches to improve planning for drought on public lands.. DroughtScape: Newsletter National Drought Mitigation Center, 16-18.
• Chu, C., Kleinhessellink, A., Havstad, K., Mcclaran, M. P., Peters, D., Vermiere, L., Wei, H., & Adler, P. (2016). Direct effects dominate responses to climate perturbations in grassland plant communities.. Nature Communications, 7, 11766. doi:10.1038/ncomms11766
• Crimmins, M. A., Crimmins, M. A., Mcclaran, M. P., & Mcclaran, M. P. (2016). Where do seasonal climate predictions belong in the drought management toolbox?. Rangelands, 38, 169-176.
• Jernigan, M. B., Mcclaran, M. P., Biedenbender, S. H., & Fehmi, J. S. (2016). Uprooted buffelgrass thatch reduces buffelgrass seedling stablishment.. Arid Land Research and Management, 30, 320-329.
• Williamson, J. C., Bestelmeyer, B. T., Mcclaran, M. P., Robinett, D., Briske, D. D., Wu, B., & Fernadez-Gimenez, M. (2016). Can ecological land classification increase the utility of vegetation monitoring data?. Ecological Indicators, 69, 657-666.
• Brugger, J., & Mcclaran, M. P. (2015). Ranchers, Forest Service, University of Arizona co-develop approaches to improve planning for drought on public lands.. DroughtScape: National Drought Mitigation Center Newsletter., 12-13.
• Mcclaran, M. P. (2015).

  Introduction to Robert R. Humphrey’s article

  . Fire Ecology, 11(2), 1-4. doi:10.4996/fireecology.1102001
• Mcclaran, M. P., Butler, G. J., Wei, H., & Ruyle, G. B. (2015). Increased preparation for drought among livestock producers reliant on rain-fed forage. Natural Hazards, 79, 151-170.
• Adler, P. B., Chu, C., Havstad, K. M., Kaplan, N., Lauenroth, W. K., McClaran, M. P., Peters, D. P., & Vermeire, L. T. (2014).

  Life form influences survivorship patterns for 109 herbaceous perennials from six semi-arid ecosystems

  . Journal of Vegetation Science, 25(4), 947-954. doi:10.1111/jvs.12106
• Chu, C., Havstad, K., Lauenroth, W., Peters, D., Mcclaran, M. P., Vermeire, L., & Adler, P. (2014). Life form influences survivorship patterns for 109 herbaceous perennials from six semi-arid ecosystems.. Journal of Vegetation Science, 25, 947-954.
• Mcclaran, M. P., & Wei, H. (2014). Recent drought phase in a 73-year record at two spatial scales: Implications for livestock production on rangelands in the Southwestern United States. Agricultural and Forest Meteorology, 197, 40-51.
• Moran, M. S., Ponce-Campos, G., Huete, A., Mcclaran, M. P., Zhang, Y., Hamerlynck, E., Augustine, D., Gunther, S., Kitchen, S., Peters, D., Starks, P. J., & Hernandez, M. (2014). Functional response of U.S. grasslands to the early 21st century drought.. Ecology, 95, 2121.
• Perlinski, A. T., Paige, G. B., & McClaran, M. P. (2014). Evaluating a State-and-Transition Model Using a Long-Term Dataset. Rangeland Ecology and Management, 67, 173-182. doi:10.2111/rem-d-12-00036.1
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  State-and-transition models (STMs) are used in natural resource management to describe ecological site scale response to natural and anthropogenic disturbances. STMs are primarily based for expert opinion and literature reviews, lacking analytical testing to support vegetation community dynamics, thresholds, and state changes. We developed a unique approach, combining ordination and permutation MANOVA (perMANOVA) with raw data interpretation, to examine vegetation data structure and identify thresholds for a STM. We used a long-term monitoring dataset for an ecological site on the Santa Rita Experimental Range, Arizona. Basal cover of perennial grasses and canopy cover of shrubs and cacti were measured on permanent transects beginning in 1957. Data were grouped by drivers identified by the STM including species invasion, grazing, drought, and mesquite treatment. Ordination by nonmetric multidimensional scaling described the structure of the data. PerMANOVA was used to test for differences between groups of sample units. Analyses of combined key species (Lehmann's lovegrass and mesquite [Prosopis velutina Woot.]) and nonkey species patterns demonstrated an irreversible transition and occurrence of a structural threshold due to Lehmann's lovegrass invasion, as well as a short-term reversible transition (restoration pathway) following mesquite treatment. Sensitivity analysis, in which key species were removed from the dataset, showed that the relative composition of nonkey species did not differ between states previously defined by the key species. This apparent disconnect between dynamics of key and nonkey species may be related to changes in the functional attributes that were not monitored during this time series. Our analyses suggest that, for this ecological site, transition to a Lehmann's lovegrass state occurs when basal cover of this species exceeds 1–2%, which often occurs within 6 yr of its arrival. Evaluation of the restoration pathway showed a recrossing of the threshold within 6 yr of treatment and when mesquite canopy cover exceeded 10%.
• Perlinski, A. T., Paige, G. B., & McClaran, M. P. (2014). Evaluating a state-and-transition model using a long-term dataset. Rangeland Ecology and Management, 67(2), 173-182.
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  Abstract: State-and-transition models (STMs) are used in natural resource management to describe ecological site scale response to natural and anthropogenic disturbances. STMs are primarily based for expert opinion and literature reviews, lacking analytical testing to support vegetation community dynamics, thresholds, and state changes. We developed a unique approach, combining ordination and permutation MANOVA (perMANOVA) with raw data interpretation, to examine vegetation data structure and identify thresholds for a STM. We used a long-term monitoring dataset for an ecological site on the Santa Rita Experimental Range, Arizona. Basal cover of perennial grasses and canopy cover of shrubs and cacti were measured on permanent transects beginning in 1957. Data were grouped by drivers identified by the STM including species invasion, grazing, drought, and mesquite treatment. Ordination by nonmetric multidimensional scaling described the structure of the data. PerMANOVA was used to test for differences between groups of sample units. Analyses of combined key species (Lehmann's lovegrass and mesquite Prosopis velutina Woot.") and nonkey species patterns demonstrated an irreversible transition and occurrence of a structural threshold due to Lehmann's lovegrass invasion, as well as a short-term reversible transition (restoration pathway) following mesquite treatment. Sensitivity analysis, in which key species were removed from the dataset, showed that the relative composition of nonkey species did not differ between states previously defined by the key species. This apparent disconnect between dynamics of key and nonkey species may be related to changes in the functional attributes that were not monitored during this time series. Our analyses suggest that, for this ecological site, transition to a Lehmann's lovegrass state occurs when basal cover of this species exceeds 1-2%, which often occurs within 6 yr of its arrival. Evaluation of the restoration pathway showed a recrossing of the threshold within 6 yr of treatment and when mesquite canopy cover exceeded 10%. © 2014 The Society for Range Management.
• Polyakov, V., Nichols, M. H., Mcclaran, M. P., & Nearing, M. (2014). Effect of check dams on runoff, sediment yield and retention on small semi-arid watersheds.. Journal of Soil and Water Conservation, 69, 414-421.
• Archer, S. R., McMurtry, C., & Mcclaran, M. P. (2013). A tool for estimating impacts of woody encroachment in arid grasslands: allometric equations for biomass, carbon and nitrogen content in Prosopis velutina. J Arid Environments, 88, 39-42.
• Bosch, D. D., Buda, A. R., Gunter, S. A., Henry McNab, W., Huete, A. R., Kitchen, S. G., McClaran, M. P., Montoya, D. S., Morgan, J. A., Nearing, M. A., Peters, D. P., Ponce Campos, G. E., Starks, P. J., Susan Moran, M., & Zhang, Y. (2013).

  Extreme precipitation patterns and reductions of terrestrial ecosystem production across biomes: ECOSYSTEM RESPONSE TO EXTREME RAINFALL

  . Journal of Geophysical Research: Biogeosciences, 118(1), 148-157. doi:10.1029/2012jg002136
• Chu, C., Havstad, K. M., Kaplan, N., Lauenroth, W. K., Mcclaran, M. P., Peters, D. P., Vermeire, L. T., & Adler, P. B. (2013). Life form influences survivorship patterns for 109 herbaceous perennials from six semi-arid ecosystems. Journal of Vegetation Science.
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  Abstract: Questions: What factors explain the variation in plant survival parameters across species and ecosystems? Location: Western North America. Methods: We compiled six long-term data sets from western North America to test for ecosystem-dependent demographic responses for forbs and grasses. Based on these data, we characterized 123 survivorship curves for 109 species. Three demographic parameters were extracted from these survivorship curves: survival rate at age 1, life expectancy at age 1, and a parameter describing the shape of the survivorship curve. We used a mixed effects model to compare the differences in demographic parameters between life forms (forbs or grasses) and among ecosystems, incorporating 'ecosystem' as a random factor, with life form treated as a categorical factor, and mean annual precipitation and mean annual temperature treated as continuous variables. Results: Grasses had higher survival and longer life expectancy than forbs at 1 yr of age. Both forbs and grasses followed Type III survivorship curves, although forbs were closer to Type II compared to the grasses. Averaging across species, hazard ratios for whole survivorship curves differed among most ecosystems. While mean annual precipitation had no effect on any demographic parameter, mean annual temperature had a significantly negative effect on both first year survival rates and life expectancy for forbs. Conclusions: Our results demonstrate that life form exerts a strong influence on demographic parameters and their response to temperature variation among ecosystems. This unprecedented information on the age-specific demography of herbaceous plants has implications for population modelling and research on life-history evolution and senescence. We compiled six long-term datasets from western North America to test for ecosystem-dependent survival patterns of forbs and grasses. We found that life form exerts a strong influence on survival parameters and their response to temperature variation among ecosystems. The age-specific demography of herbaceous plants has implications for population modeling and research on life history evolution and senescence. © 2013 International Association for Vegetation Science.
• E., G., Moran, M. S., Huete, A., Zhang, Y., Bresloff, C., Huxman, T. E., Eamus, D., Bosch, D. D., Buda, A. R., Gunter, S. A., Scalley, T. H., Kitchen, S. G., Mcclaran, M. P., Mcnab, W. H., Montoya, D. S., Morgan, J. A., P., D., Sadler, E. J., Seyfried, M. S., & Starks, P. J. (2013). Ecosystem resilience despite large-scale altered hydroclimatic conditions. Nature, 494(7437), 349-352.
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  PMID: 23334410;Abstract: Climate change is predicted to increase both drought frequency and duration, and when coupled with substantial warming, will establish a new hydroclimatological model for many regions. Large-scale, warm droughts have recently occurred in North America, Africa, Europe, Amazonia and Australia, resulting in major effects on terrestrial ecosystems, carbon balance and food security. Here we compare the functional response of above-ground net primary production to contrasting hydroclimatic periods in the late twentieth century (1975-1998), and drier, warmer conditions in the early twenty-first century (2000-2009) in the Northern and Southern Hemispheres. We find a common ecosystem water-use efficiency (WUE e: Above-ground net primary production/ evapotranspiration) across biomes ranging from grassland to forest that indicates an intrinsic system sensitivity to water availability across rainfall regimes, regardless of hydroclimatic conditions. We found higher WUE e in drier years that increased significantly with drought to a maximum WUE e across all biomes; and a minimum native state in wetter years that was common across hydroclimatic periods. This indicates biome-scale resilience to the interannual variability associated with the early twenty-first century drought - that is, the capacity to tolerate low, annual precipitation and to respond to subsequent periods of favourable water balance. These findings provide a conceptual model of ecosystem properties at the decadal scale applicable to the widespread altered hydroclimatic conditions that are predicted for later this century. Understanding the hydroclimatic threshold that will break down ecosystem resilience and alter maximum WUE e may allow us to predict land-surface consequences as large regions become more arid, starting with water-limited, low-productivity grasslands. © 2013 Macmillan Publishers Limited. All rights reserved.
• Gold, A. J., Gold, A. J., Parker, D., Parker, D., Waskom, R. M., Waskom, R. M., Dobrowolski, J., Dobrowolski, J., O'Neill, M., O'Neill, M., Groffman, P. M., Groffman, P. M., Addy, K., Addy, K., Barber, M., Barber, M., Batie, S., Batie, S., Benham, B., , Benham, B., et al. (2013). Advancing water resource management in agricultural, rural, and urbanizing watersheds: why land-grant universities matter. Journal of Soil and Water Conservation, 68(4), 337-348.
• Gold, A. J., Parker, D., Waskom, R. M., Dobrowolski, J., O'Neill, M., Groffman, P. M., Addy, K., Barber, M., Batie, S., Benham, B., Bianchi, M., Blewett, T., Evensen, C., Farrell-Poe, K., Gardner, C., Graham, W., Harrison, J., Harter, T., Kushner, J., , Lowrance, R., et al. (2013). Advancing water resource management in agricultural, rural, and urbanizing watersheds: Why land-grant universities matter. Journal of Soil and Water Conservation, 68(4), 337-348.
• McClaran, M. P., McMurtry, C. R., & Archer, S. R. (2013). A tool for estimating impacts of woody encroachment in arid grasslands: Allometric equations for biomass, carbon and nitrogen content in Prosopis velutina. Journal of Arid Environments, 88, 39-42.
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  Abstract: Regression equations were developed to estimate above ground biomass and carbon and nitrogen mass of foliage and stem size fractions from plant size dimensions (basal diameter, canopy area, height, canopy volume) for a tall shrub species (Prosopis velutina) that has increased in abundance in arid and semi-arid grasslands in the southwestern United States and northwestern Mexico. Regression equations were also developed to describe relationships among the dimensions of plant size. All equations were significant (p < 0.001); and all but two had r2 values >0.72. In addition to species-specific information, we found support for the global patterns of foliar biomass increasing to the 3/4 power of stem biomass and height increasing to the 1/2 power of stem diameter. We provide a comprehensive report of all equations, which can support a variety of in situ (ground-based), modeling, and remote-sensing objectives related to quantifying changes in ecosystem function and carbon sequestration accompanying changes in woody plant abundance. We advocate that comprehensive reporting should become more common for arid and semi-arid woody species in order to support a broad spectrum of users while laying the foundation for the development of global generalizations similar to those available for forest trees. © 2012 Elsevier Ltd.
• Mcclaran, M. P., McMurtry, C., & Archer, S. R. (2013). A tool for estimating impacts of woody encroachment in arid grasslands: allometric equations for biomass, carbon and nitrogen content in Prosopis velutina.. Journal of Arid Environments, 88, 39-42.
• Moore, P. E., W., J., Yee, J. L., McClaran, M. P., Cole, D. N., McDougald, N. K., & Brooks, M. L. (2013). Net primary productivity of subalpine meadows in yosemite national park in relation to climate variability. Western North American Naturalist, 73(4), 409-418.
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  Abstract: Subalpine meadows are some of the most ecologically important components of mountain landscapes, and primary productivity is important to the maintenance of meadow functions. Understanding how changes in primary productivity are associated with variability in moisture and temperature will become increasingly important with current and anticipated changes in climate. Our objective was to describe patterns and variability in aboveground live vascular plant biomass in relation to climatic factors. We harvested aboveground biomass at peak growth from four 64-mplots each in xeric, mesic, and hydric meadows annually from 1994 to 2000. Data from nearby weather stations provided independent variables of spring snow water content, snow-free date, and thawing degree days for a cumulative index of available energy. We assembled these climatic variables into a set of mixed effects analysis of covariance models to evaluate their relationships with annual aboveground net primary productivity (ANPP), and we used an information theoretic approach to compare the quality of fit among candidate models. ANPP in the xeric meadow was negatively related to snow water content and thawing degree days and in the mesic meadow was negatively related to snow water content. Relationships between ANPP and these 2 covariates in the hydric meadow were not significant. Increasing snow water content may limit ANPP in these meadows if anaerobic conditions delay microbial activity and nutrient availability. Increased thawing degree days may limit ANPP in xeric meadows by prematurely depleting soil moisture. Large within-year variation of ANPP in the hydric meadow limited sensitivity to the climatic variables. These relationships suggest that, under projected warmer and drier conditions, ANPP will increase in mesic meadows but remain unchanged in xeric meadows because declines associated with increased temperatures would offset the increases from decreased snow water content. © 2013.
• Moore, P. E., van Wagtendonk, J., Yee, J. L., Mcclaran, M. P., Cole, D. N., McDougald, N. K., & Brooks, M. L. (2013). Net primary productivity of subalpine meadows in Yosemite National Park in relation to climate variability.. Western North American Naturalist.
• Ponce-Campos, G. E., Moran, M. S., Huete, A., Zhang, Y., Bresloff, C., Huxman, T., McNab, D. E., Bosh, D. D., Buda, A. R., Gunther, S. A., Scalley, T. H., Kitchen, S., Mcclaran, M. P., Montoya, D. S., Morgan, J. A., Peters, D., Sadler, E. J., Seyfried, M. S., & Starks, P. J. (2013). Ecosystem resilience despite large-scale altered hydroclimatic condition.. Nature.
• Zhang, Y., Moran, M. S., Nearing, M. A., E., G., Huete, A. R., Buda, A. R., Bosch, D. D., Gunter, S. A., Kitchen, S. G., McNab, W. H., Morgan, J. A., McClaran, M. P., Montoya, D. S., Peters, D. P., & Starks, P. J. (2013). Extreme precipitation patterns and reductions of terrestrial ecosystem production across biomes. Journal of Geophysical Research G: Biogeosciences, 118(1), 148-157.
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  Abstract: Precipitation regimes are predicted to shift to more extreme patterns that are characterized by more heavy rainfall events and longer dry intervals, yet their ecological impacts on vegetation production remain uncertain across biomes in natural climatic conditions. This in situ study investigated the effects of these climatic conditions on aboveground net primary production (ANPP) by combining a greenness index from satellite measurements and climatic records during 2000-2009 from 11 long-term experimental sites in multiple biomes and climates. Results showed that extreme precipitation patterns decreased the sensitivity of ANPP to total annual precipitation (PT) at the regional and decadal scales, leading to decreased rain use efficiency (RUE; by 20% on average) across biomes. Relative decreases in ANPP were greatest for arid grassland (16%) and Mediterranean forest (20%) and less for mesic grassland and temperate forest (3%). The cooccurrence of heavy rainfall events and longer dry intervals caused greater water stress conditions that resulted in reduced vegetation production. A new generalized model was developed using a function of both PT and an index of precipitation extremes and improved predictions of the sensitivity of ANPP to changes in precipitation patterns. Our results suggest that extreme precipitation patterns have substantially negative effects on vegetation production across biomes and are as important as P T. With predictions of more extreme weather events, forecasts of ecosystem production should consider these nonlinear responses to altered extreme precipitation patterns associated with climate change. Key Points Extreme rainfall events reduced the sensitivity of ANPP to total annual rainfallCo-occurrence of intense rainfall and longer dry interval reduced greater ANPPA new model improved predictions of ANPP by accounting for extreme patterns ©2012. American Geophysical Union. All Rights Reserved.
• Zhang, Y., Moran, M. S., Nearing, M. A., Ponce-Campos, G. E., Huete, A. R., Buda, A. R., Bosh, D. D., Gunther, S. A., Kitchen, S., McNabb, W. H., Morgan, J. A., Mcclaran, M. P., Montoya, D. S., Peters, D., & Starks, P. J. (2013). Extreme precipitation patterns reduced terrestrial ecosystem production across biomes.. Journal of Geophysical Research-Biogeosciences.
• Anderson, J., McClaran, M., & Adler, P. (2012). Cover and density of semi-desert grassland plants in permanent quadrats mapped from 1915 to 1947. Ecology, 93, 1492.
• Bagchi, A., Briske, D., Wu, X., McClaran, M., Bestelmeyer, B., & Fernandez-Gimenez, M. (2012). Empirical assessment of state-and-transition models with a long-term vegetation record from the Sonoran Desert. Ecological Applications, 22, 400-411.
• Bagchi, S., Briske, D. D., Wu, X. B., McClaran, M. P., Bestelmeyer, B. T., & Fernández-Giménez, M. E. (2012). Empirical assessment of state-and-transition models with a long-term vegetation record from the Sonoran Desert. Ecological Applications, 22(2), 400-411.
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  PMID: 22611843;Abstract: Resilience-based frameworks, including state-and-transition models (STM), are being increasingly called upon to inform policy and guide ecosystem management, particularly in rangelands. Yet, multiple challenges impede their effective implementation: (1) paucity of empirical tests of resilience concepts, such as alternative states and thresholds, and (2) heavy reliance on expert models, which are seldom tested against empirical data. We developed an analytical protocol to identify unique plant communities and their transitions, and applied it to a long-term vegetation record from the Sonoran Desert (1953-2009). We assessed whether empirical trends were consistent with resilience concepts, and evaluated how they may inform the construction and interpretation of expert STMs. Seven statistically distinct plant communities were identified based on the cover of 22 plant species in 68 permanent transects. We recorded 253 instances of community transitions, associated with changes in species composition between successive samplings. Expectedly, transitions were more frequent among proximate communities with similar species pools than among distant communities. But unexpectedly, communities and transitions were not strongly constrained by soil type and topography. Only 18 transitions featured disproportionately large compositional turnover (species dissimilarity ranged between 0.54 and 0.68), and these were closely associated with communities that were dominated by the common shrub (burroweed, Haplopappus tenuisecta); indicating that only some, and not all, communities may be prone to large compositional change. Temporal dynamics in individual transects illustrated four general trajectories: stability, nondirectional drift, reversibility, and directional shifts that were not reversed even after 2-3 decades. The frequency of transitions and the accompanying species dissimilarity were both positively correlated with fluctuation in precipitation, indicating that climatic drivers require more attention in STMs. Many features of the expert models, including the number of communities and participant species, were consistent with empirical trends, but expert models underrepresented recent increases in cacti while overemphasizing the introduced Lehmann's lovegrass (Eragrostis lehmanniana). Quantification of communities and transitions within long-term vegetation records presents several quantitative metrics such as transition frequency, magnitude of accompanying compositional change, presence of unidirectional trajectories, and lack of reversibility within various timescales, which can clarify resilience concepts and inform the construction and interpretation of STMs. © 2012 by the Ecological Society of America.
• Butler, G., Ruyle, G. B., Mcclaran, M. P., & Austin, D. E. (2012). Ranching with drought.. Arizona Cattlelog, 66(8), 16-17.
• Mcclaran, M. P. (2012). Santa Rita Experimental Range Long Term Transect Database. Biodiversity & Ecology, 4, 435.
• Olsson, A. D., Betancourt, J., Mcclaran, M. P., & Marsh, S. E. (2012). Sonoran Desert Ecosystem transformation by a C ₄ grass without the grass/fire cycle. Diversity and Distributions, 18(1), 10-21.
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  Abstract: Aim Biological invasions facilitate ecosystem transformation by altering the structure and function, diversity, dominance and disturbance regimes. A classic case is the grass-fire cycle in which grass invasion increases the frequency, scale and/or intensity of wildfires and promotes the continued invasion of invasive grasses. Despite wide acceptance of the grass-fire cycle, questions linger about the relative roles that interspecific plant competition and fire play in ecosystem transformations. Location Sonoran Desert Arizona Upland of the Santa Catalina Mountains, Arizona, USA. Methods We measured species cover, density and saguaro (Carnegiea gigantea) size structure along gradients of Pennisetum ciliare invasion at 10 unburned/ungrazed P. ciliare patches. Regression models quantified differences in diversity, cover and density with respect to P. ciliare cover, and residence time and a Fisher's exact test detected demographic changes in saguaro populations. Because P. ciliare may have initially invaded locations that were both more invasible and less diverse, we ran analyses with and without the plots in which initial infestations were located. Results Richness and diversity decreased with P. ciliare cover as did cover and density of most dominant species. Richness and diversity declined with increasing time since invasion, suggesting an ongoing transformation. The proportion of old-to-young Carnegiea gigantea was significantly lower in plots with dominant P. ciliare cover. Main conclusions Rich desert scrub (15-25 species per plot) was transformed into depauperate grassland (2-5 species per plot) within 20years following P. ciliare invasion without changes to the fire regime. While the onset of a grass-fire cycle may drive ecosystem change in the later stages and larger scales of grass invasions of arid lands, competition by P. ciliare can drive small-scale transformations earlier in the invasion. Linking competition-induced transformation rates with spatially explicit models of spread may be necessary for predicting landscape-level impacts on ecosystem processes in advance of a grass-fire cycle. © 2011 Blackwell Publishing Ltd.
• Olsson, A., Betancourt, J., McClaran, M., & Marsh, S. (2012). Sonoran desert ecosystem transformation by a C4 grass without the grass/fire cycle. Diversity and Distributions, 18, 10-21.
• Goodrich, D., Guertin, D., Burns, I., Nearing, M., Stone, J., Wei, H., Heilman, P., Hernandez, M., Speath, K., Pierson, F., Page, G., Miller, S., Kepner, W., Ruyle, G., McClaran, M., Weltz, M., & Jolley, L. (2011). AGWA: The automated geospatial watershed assessment tool to inform rangeland management. Rangelands, 33(4), 41-47.
• Huang, C., Archer, S., McClaran, M., & Marsh, S. (2011). Long-term cross-scale assessment of woody cover stability in drylands. 34th International Symposium on Remote Sensing of Environment - The GEOSS Era: Towards Operational Environmental Monitoring.
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  Abstract: Grasslands and savannas characterize much of the world's dryland ecosystems. Various lines of evidence indicate the grass/shrub balance in these systems has destabilized in the recent decades. Here, we link long-term field and remote sensing observations to quantify woody plant dynamics at a site in the southwestern USA where Prosopis velutina has proliferated in semi-desert grassland. Field records revealed that the overall trend can be dissected into three phases: Rapid expansion (1957-1991), abrupt decline (1991-1997) and stabilization (1997-2006). The contributions of land histories and topo-edaphic factors to the trend were complex. Remote sensing observations indicated net declines in woody cover since 1984. Some of these occurred at sites with recent fires, whereas others may reflect density dependent dynamics. Notable exceptions occurred at low elevations where cacti proliferated. This study confirms that temporal and spatial dynamics of woody cover change are not unidirectional and are influenced by complex combinations of factors.
• Ponce, G., Moran, S., Huete, A., Bresloff, C., Huxman, T., Bosch, D., Bradford, J., Buda, A., Gunter, S., McNab, H., McClaran, M., Peters, D., Sadler, J., Seyfried, M., Starks, P., Montoya, D. S., & Heartsill, T. (2011). Convergence of dynamic vegetation net productivity responses to precipitation variability from 10 years of MODIS EVI. 34th International Symposium on Remote Sensing of Environment - The GEOSS Era: Towards Operational Environmental Monitoring.
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  Abstract: According to Global Climate Models (GCMs) the occurrence of extreme events of precipitation will be more frequent in the future. Therefore, important challenges arise regarding climate variability, which are mainly related to the understanding of ecosystem responses to changes in precipitation patterns. Previous studies have found that Above-ground Net Primary Productivity (ANPP) was positively related to increases in annual precipitation and this relation may converge across biomes during dry years. One challenge in studying this ecosystem response at the continental scale is the lack of ANPP field measurements over extended areas. In this study, the MODIS EVI was utilized as a surrogate for ANPP and combined with precipitation datasets from twelve different experimental sites across the United States over a 10-year period. Results from this analysis confirmed that integrated-EVI for different biomes converged toward common precipitation use efficiency during water-limited periods and may be a viable surrogate for ANPP measurements for further ecological research.
• McClaran, M. P., Nearing, M. A., Nichols, M. H., Polyakov, V. O., Scott, R. L., & Stone, J. J. (2010).

  Long-term runoff and sediment yields from small semiarid watersheds in southern Arizona: RUNOFF AND SEDIMENT YIELDS FROM SEMIARID WATERSHEDS

  . Water Resources Research, 46(9). doi:10.1029/2009wr009001
• Polyakov, V. O., Nearing, M. A., Nichols, M. H., Scott, R. L., Stone, J. J., & McClaran, M. P. (2010). Long-term runoff and sediment yields from small semiarid watersheds in southern Arizona. Water Resources Research, 46(9).
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  Abstract: This study presents analysis of 34 years of precipitation, runoff, and sediment data collected from eight small (1.1-4.0 ha) semiarid rangeland watersheds in southern Arizona, USA. Average annual precipitation ranged between 354 and 458 mm with 53% of the total rainfall occurring from July through September. Runoff depth was 3.5%-13.9% of annual precipitation depth for individual watersheds and 9.2% on average. Runoff events with missing sediment data were estimated to account for 30% of the total sediment yield. Sediment yields were highly variable, ranging between 0.85 t ha-1 yr -1 and 6.69 t ha-1 yr-1 with an average of 2.4 t ha-1 yr-1. Ten percent of rainfall events with the largest sediment yields produced over 50% of the total sediment yield during the 34 year period. Linear regression models were developed to relate precipitation and runoff characteristics to watershed sediment yield. Maximum 30 min precipitation intensity was the primary factor affecting runoff, and runoff was the best predictor for sediment yield, explaining up to 90% of its variability. Fire and drought may have significantly altered the hydrologic and sediment response on some of the watersheds, but lack of continuous monitoring of vegetation on the watershed areas complicated interpretation of both fire and grazing management effects. Copyright 2010 by the American Geophysical Union.
• Moran, M. S., Hutchinson, B. S., Marsh, S. E., McClaran, M. P., & Olsson, A. D. (2009). Archiving and distributing three long-term interconnected geospatial data sets. IEEE Transactions on Geoscience and Remote Sensing, 47(1), 59-71.
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  Abstract: Repeat remote sensing field campaigns at experimental sites result in a valuable set of remote sensing data resources, geographic information system data sets, digitized maps, and tabular data that are tied to specific locations. Archiving and distributing these geospatial data generally become the responsibility of local universities and federal research centers with few resources dedicated to the task. The developments in archiving and distributing geospatial data are presented through the description and discussion of three interconnected case studies of data preservation at government and academic units in southeastern Arizona. The main challenges were associated with data archiving, developing online data distribution systems, interconnecting the data distribution systems, and sustaining the archiving and distribution systems. The case studies present multiple approaches to meeting these challenges within the constraints of government and academic units. Results should guide other local efforts to archive and preserve long-term geospatial data and distribute them online. © 2006 IEEE.
• Nafus, A. M., McClaran, M. P., Archer, S. R., & Throop, H. L. (2009). Multispecies allometric models predict grass biomass in semidesert rangeland. Rangeland Ecology and Management, 62(1), 68-72.
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  Abstract: Multispecies allometric models to predict grass biomass may increase field study efficiency by eliminating the need for species-specific data. We used field measurements during two growing seasons to develop single-species and multispecies regression models predicting the current year's aboveground biomass for eight common cespitose grass species. Simple and stepwise regression analyses were based on natural log expressions of biomass, basal diameter, and height, and a dummy variable expression of grazing history. Basal diameter had the strongest relationship with biomass among single-species (adjusted R 2 = 0.80 to 0.91) and multispecies (adjusted R2 50.85) models. Regression slopes (b) for diameter among single-species (b = 1.01 to 1.49) and the multispecies (b = 1.25) models suggests that biomass will double when diameter increases ∼75%. Height and grazing history added little predictive value when diameter was already in the model. When applied to actual populations, biomass estimates from multispecies models were within 3-29% of estimates from the single-species models. Although the multispecies biomass-size relationship was robust across the cespitose life-form, users should be cautious about applying our equations to different locations, plant sizes, and population size-structures.
• Adams, M. B., Adams, M. R., Mcclaran, M. P., Moran, M. S., Nichols, M. H., & Peters, D. P. (2008).

  Long‐term data collection at USDA experimental sites for studies of ecohydrology

  . Ecohydrology, 1(4), 377-393. doi:10.1002/eco.24
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  The science of ecohydrology is characterized by feedbacks, gradual trends and extreme events that are best revealed with long-term experimental studies of hydrological processes and biological communities. In this review, we identified 81 US Department of Agriculture (USDA) experimental watersheds, forests and ranges with data records of more than 20 years measuring important ecosystem dynamics such as variations in vegetation, precipitation, climate, runoff, water quality and soil moisture. Through a series of examples, we showed how USDA long-term data have been used to understand key ecohydrological issues, including (1) time lag between cause and effects, (2) critical thresholds and cyclic trends, (3) context of rare and extreme events and (4) mechanistic feedbacks for simulation modelling. New analyses of network-wide, long-term data from USDA experimental sites were used to illustrate the potential for multi-year, multi-site ecohydrological research. Three areas of investigation were identified to best exploit the unique spatial distribution and long-term data of USDA experimental sites: convergence, cumulative synthesis and autocorrelation. This review underscored the need for continuous, interdisciplinary data records spanning more than 20 years across a wide range of ecosystems within and outside the conterminous USA to address major crosscutting problems facing ecohydrology. Conversely, the heightened interest in ecohydrology has impacted USDA experimental sites by encouraging new long-term data collection efforts and adapting existing long-term data collection networks to address new science issues. Copyright © 2008 John Wiley & Sons, Ltd.
• Bolton, G. H., & McClaran, M. P. (2008). Evaluating sustainability of Symplocos ramosissima harvest for herder huts: A case study near an upper-elevation village in Nepal. Mountain Research and Development, 28(3-4), 248-254.
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  Abstract: Upper-elevation villagers in Nepal harvest large numbers of 5-10 cm diameter trees to construct itinerant herders' shelters. The harvest of these poles, as well as fuelwood and tree-leaf livestock fodder, may be altering upper-elevation forest structure and resource availability in Nepal. Near a village in west-central Nepal, we evaluated the sustainability of Symplocos ramosissima poles harvested for herders' shelter construction by comparing estimates of harvest and replenishment rates under 4 scenarios of spatial distribution of harvest within 3 equal-area forest types: 1) harvest evenly distributed, 2) harvest only in forest type closest to area of hut construction, 3) harvest in two closest forest types, 4) harvest in each forest type proportional to recent use patterns, as deduced from the density of stumps of pole-sized S. ramosissima. Mean density ± SE of pole-size S. ramosissima was 375 ± 32 stems ha-1. Tree-ring analysis of 24 pole-size S. ramosissima indicated a mean age of 35 years and a mean of 11 years to grow from 5 cm to 10 cm dbh. Comparisons of harvest and replenishment rates suggest that only harvest scenario 1 (even distribution) was sustainable. Harvest scenario 2 (closest forest type) and scenario 3 (two closest forest types) were unsustainable, Harvest scenario 4 proportional to stump density) was sustainable in the two farther forest types, but unsustainable in the forest type closest to agricultural fields.
• Browning, D. M., Archer, S. R., Asner, G. P., McClaran, M. P., & Wessman, C. A. (2008). Woody plants in grasslands: Post-encroachment stand dynamics. Ecological Applications, 18(4), 928-944.
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  PMID: 18536253;Abstract: Woody plant abundance is widely recognized to have increased in savannas and grasslands worldwide. The lack of information on the rates, dynamics, and extent of increases in shrub abundance is a major source of uncertainty in assessing how this vegetation change has influenced biogeochemical cycles. Projecting future consequences of woody cover change on ecosystem function will require knowledge of where shrub cover in present-day stands lies relative to the realizable maximum for a given soil type within a bioclimatic region. We used time-series aerial photography (1936, 1966, and 1996) and field studies to quantify cover and biomass of velvet mesquite (Prosopis velutina Woot.) following its proliferation in a semidesert grassland of Arizona. Mapping of individual shrubs indicated an encroachment phase characterized by high rates of bare patch colonization. Upon entering a stabilization phase, shrub cover increases associated with recruitment and canopy expansion were largely offset by contractions in canopy area of other shrub patches. Instances of shrub disappearance coincided with a period of below-average rainfall (1936-1966). Overall, shrub cover (mean ± SE) on sandy uplands with few and widely scattered shrubs in 1902 was dynamically stable over the 1936-1996 period averaging ∼35% ± 5%. Shrub cover on clayey uplands in 1936 was 17% ± 2% but subsequently increased twofold to levels comparable to those on sandy uplands by 1966 (36% ± 7%). Cover on both soils then decreased slightly between 1966 and 1996 to 28% ± 3%. Thus, soil properties influenced the rate at which landscapes reached a dynamic equilibrium, but not the apparent endpoint. Although sandy and clayey landscapes appear to have stabilized at comparable levels of cover, shrub biomass was 1.4 times greater on clayey soils. Declines in shrub cover between 1966 and 1996 were accompanied by a shift to smaller patch sizes on both sandy and clayey landscapes. Dynamics observed during the stabilization phase suggest that density-dependent regulation may be in play. If woody cover has transitioned from directional increases to a dynamic equilibrium, biomass projections will require monitoring and modeling patch dynamics and stand structure rather than simply changes in total cover. © 2008 by the Ecological Society of America.
• Haren, J. V., Marsh, S. E., Martens, D. A., Mcclaran, M. P., & Moore-kucera, J. (2008).

  Soil carbon and nitrogen in relation to shrub size and death in a semi-arid grassland

  . Geoderma, 145(1), 60-68. doi:10.1016/j.geoderma.2008.02.006
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  Abstract Nutrient accumulation as fertile islands beneath invasive trees and shrubs in grasslands may provide opportunities for carbon sequestration. In a southwestern USA grassland, our objectives were to describe 1) the accumulation beneath Prosopis velutina (velvet mesquite) and isolated grass plants, and 2) the loss of accumulated nutrients 40 y after P. velutina death. We compared organic carbon (OC), total nitrogen (TN) and δ13C in soil organic matter among large living, large dead, and small living P. velutina and open grassland, and between grass plants and bare ground. Soil samples were collected at 0–5, 5–10, 16.8–23.2, and 36.8–43.2 cm depths, and separated into five size/density fractions: particulate organic matter (Macro- and Micro-POM), mineral associated organic matter (Micro-MAOM), Silt, and Clay. We expected that differences in OC, TN, and δ13C among soil fractions would suggest mechanisms and rates of accumulation with P. velutina persistence and loss following P. velutina death. Soil OC and TN accumulation was ~ 80–750% greater for large P. velutina than open grassland for whole soil and 4 of 5 fractions at 0–5 cm depth, but only 50–250% greater at 5–10 cm depth for whole soil and 3 of 5 fractions. Total OC and TN accumulation at 0–10 cm depth was 6.12 kg C m− 2 and 0.55 kg N m− 2, respectively. Accumulation did not occur in whole soil or any fraction at 16.8–23.2 cm and 36.8–43.2 cm depths, or in the Micro-MAOM fraction at any depth. Accumulation under small P. velutina was less than large plants, and not significantly different from open grassland. Beneath isolated grass plants, accumulation of TN occurred at 0–5 cm depth, and OC accumulation at 0–5 and 5–10 cm depths in whole soils only, but change in δ13C did not accompany accumulations. Forty years after death of large P. velutina, 67–106% of accumulated OC and TN were lost from whole soil and soil fractions at 0–5 cm depth. At 5–10 cm depth, loss (78–93%) was only detected in whole soils. Greater accumulation of OC and TN in the POM than the Silt and Clay fractions is consistent with the large physical size of recent organic matter inputs from P. velutina, but no differences in loss rates among fractions following P. velutina death suggests density dependent rates of organic matter consumption. Declines in δ13C accompanied OC accumulation and increases occurred during loss. A 20–30 y mean residence time (MRT) for whole soil and the Clay fraction over those 40 y is suggested by changes in OC and δ13C, but MRT based on changes in OC and δ13C differ for Macro-POM (1–3 y versus 20–25 y, respectively) and Silt (> 50 y versus 20–30 y, respectively). Activities that remove P. velutina should focus on small plants and protect large plants thereby maintaining their carbon sequestration potential.
• Mashiri, F. E., McClaran, M. P., & Fehmi, J. S. (2008). Short- and long-term vegetation change related to grazing systems, precipitation, and mesquite cover. Rangeland Ecology and Management, 61(4), 368-379.
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  Abstract: Rangeland scientists struggle with how long rangeland experiments must continue in order to detect treatment effects, particularly in semiarid ecosystems characterized by slow responses and high spatiotemporal variability. We compared changes in eight grass and three shrub categories to grazing systems (yearlong vs. seasonal rotation with equivalent long-term stocking rates), and covariates (precipitation and mesquite [Prosopis velutina] gradients) over 12 yr (1972-1984) and 34 yr (1972-2006) on the Santa Rita Experimental Range, Arizona. We used split-plot analysis of variance, with year as the split, to make these comparisons. Grazing systems did not influence plant dynamics as shown by the lack of grazing system by year effect on all response variables in either time period. The absence of a detectable grazing effect on vegetation changes may be due to overriding influences of grazing intensity, pasture size, precipitation variability, and few replicates. Also, more time may be needed to detect the small accumulating and potentially temporary effects from grazing systems. The grazing system main effects present at the beginning and throughout the study suggest that pastures assigned to each grazing system had different potentials to support vegetation. Nearly twice the number of response variables were related to the precipitation covariate than to mesquite cover, but only about half of all the relationships were consistent between time periods. The struggle to know how long to observe before detecting a grazing system effect was not resolved with the additional 22 yr of observation because we cannot definitively reject that either more time is needed to detect small but cumulative effects or that the two grazing systems are not different.
• McLain, J. E., Martens, D. A., & McClaran, M. P. (2008). Soil cycling of trace gases in response to mesquite management in a semiarid grassland. Journal of Arid Environments, 72(9), 1654-1665.
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  Abstract: Over the last century, proliferation of velvet mesquite (Prosopis velutina) in Southwestern grasslands has led to mesquite removal to increase livestock forage, but the effects of mesquite on the fluxes of C- and N-based gases are not well understood. We report soil surface fluxes and porespace concentrations of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) over two monsoon seasons beneath mesquite canopy (LIVE), in open grassland (OPEN), and under a mesquite skeleton (DEAD) in Southeastern Arizona. In 2003, CO2 production was not different among sites, but on three 2004 measurement dates, CO2 production was greatest from LIVE. In both years, N2O production was highest in LIVE in early monsoon, while CH4 production dominated in OPEN and DEAD sites. CH4 consumption increased in all sites as the summer progressed, resulting in net monsoon CH4 fluxes near zero. Over both years, temperature and precipitation accounted for significant variability in CO2 flux and precipitation correlated with N2O production. Soil moisture accounted for significant variability in CH4 flux in 2003. Observed variations in trace gas dynamics suggest that several years of measurements would be required to accurately predict mesquite management effects on trace gas flux in Southwestern rangelands. © 2008 Elsevier Ltd. All rights reserved.
• Huang, C., Marsh, S. E., McClaran, M. P., & Archer, S. R. (2007). Postfire stand structure in a semiarid savanna: Cross-scale challenges estimating biomass. Ecological Applications, 17(7), 1899-1910.
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  PMID: 17974330;Abstract: Algorithms relating remotely sensed woody cover to biomass are often the basis for large-scale inventories of aboveground carbon stocks. However, these algorithms are commonly applied in a generic fashion without consideration of disturbances that might alter vegetation structure. We compared field and remote sensing estimates of woody biomass on savannas with contrasting disturbance (fire) histories and assessed potential errors in estimating woody biomass from cover without considering fire history. Field surveys quantified multilayer cover (MLC) of woody and succulent plants on sites experiencing wildfire in 1989 or 1994 and on nearby unburned (control) sites. Remote sensing estimates of the woody cover fraction (WCF) on burned and control sites were derived from contemporary (2005) dry-season Landsat Thematic Mapper imagery (during a period when herbaceous cover was senescent) using a probabilistic spectral mixture analysis model. Satellite WCF estimates were compared to field MLC assessments and related to aboveground biomass using allometry. Field-based MLC and remotely sensed WCFs both indicated that woody cover was comparable on control areas and areas burned 11-16 years ago. However, biomass was approximately twofold higher on control sites. Canopy cover was a strong predictor of woody biomass on burned and control areas, but fire history significantly altered the linear cover-biomass relationship on control plots to a curvilinear relationship on burned plots. Results suggest predictions of woody biomass from "generic" two-dimensional (2-D) cover algorithms may underestimate biomass in undisturbed stands and overestimate biomass in stands recovering from disturbance. Improving the accuracy of woody-biomass estimates from field and/or remotely sensed cover may therefore require disturbance-specific models or detection of vegetation height and transforming 2-D vegetation cover to 3-D vegetation volume. © 2007 by the Ecological Society of America.
• McClaran, M. P., & Angell, D. L. (2007). Mesquite and grass relationships at two spatial resolutions. Plant Ecology, 191(1), 119-126.
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  Abstract: Relationships between woody plants and grass are typically described at either the stand (≥100 m2) or plant (≤10 m2) spatial resolutions. Descriptions of the Prosopis velutina (mesquite)-grass relationships in the North American Desert Grassland differ between spatial scales: P. velutina often inhibits grass at the stand scale compared to facilitation or neutral relations at the plant scale. We use simultaneous measures of grass density at both spatial resolutions (made at 3 y intervals from 1997 to 2003) to evaluate the influence of the spatial resolution on detecting P. velutina-grass relationships. We confine our observations to the parsimonious conditions of (1) two distinct P. velutina age classes that are exclusive occupants of study sites and (2) total cover of P. velutina was not different between study sites in 2000 and 2003. Thus, total P. velutina cover is constant in those 2 years but P. velutina ages contributing to that cover differed between the study sites. We confirmed the importance of spatial scale because no grass species was related to P. velutina age at the stand scale, but 2 of 5 species were significantly related at the plant scale. Aristida spp. was greater under young than old P. velutina, and Muhlenbergia porteri was greater under old P. velutina. These results suggest that the influence of old P. velutina on grass abundance is restricted to the area under the canopy and does not extend into inter-canopy areas, and therefore the observations at the stand scale may not detect the P. velutina-grass relationships at the plant scale. © 2006 Springer Science+Business Media, Inc.
• McClaran, M. P., & Angell, D. L. (2006). Long-term vegetation response to mesquite removal in Desert Grassland. Journal of Arid Environments, 66(4), 686-697.
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  Abstract: Forty-six years of vegetation response to mesquite removal at dry, low elevation sites on the Santa Rita Experimental Range in southern Arizona was only slightly different than the vegetation dynamics where mesquite trees were left intact. Only the density of threeawn grass species (Aristida spp.) was greater in the mesquite removal areas: and that difference persisted even after the cover of mesquite was no longer different between treatment and control areas. Cover of shrubs and perennial grasses, and density of all other perennial grasses did not differ between mesquite treatments throughout the study period. Mesquite cover on treated areas was not different than untreated areas 40 years after tree removal. The long-term results support the interpretation that vegetation dynamics at these dry locations, are not limited by the abundance of neighbouring mesquite. Alternatively, mesquite abundance is self-limiting at levels less than would influence grass abundance and precipitation anomalies may override any effects of neighbouring mesquite. Practically, these results suggest that areas with {less-than or slanted equal to}350 mm year-1 of annual precipitation and
• Mcclaran, M. P., Smith, S. E., & Ward, J. P. (2006).

  Water requirements for emergence of buffelgrass (Pennisetum ciliare)

  . Weed Science, 54(4), 720-725. doi:10.1614/ws-05-163r1.1
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  Abstract The ability of an invasive species to acquire and use a limiting resource during critical life history stages governs its ability to establish and persist within an environment. Arid environments are generally considered more resistant to invasion and are defined by low and sporadic precipitation. Warm-season grasses are most susceptible to mortality during seedling emergence, but water requirements for emergence are rarely known. We examined the ability of the often invasive warm-season grass, buffelgrass, to emerge given a range of simulated precipitation delivered on 2, 3, and 4 consecutive days with the use of a line-source irrigation system in a glasshouse. The minimum amount of water required for buffelgrass emergence was observed to be 6.3 mm (3.14 mm on 2 consecutive days). With the use of probit analysis, the median emergence response (0.5 emergence probability) was predicted to require 17.4–19.9 mm of water. Emergence was concentrated within the first 5 days following initial simulated ...
• Tanzer, L. S., & McClaran, M. P. (2006). Distinguishing hyperbole from action in corporate strategic responses to global climate change. Electric Utilities Environmental Conference, EUEC 2005: 8th Annual Joint EPA, DOE, EEI, EPRI Conference on Air Quality, Global Climate Change and Renewable Energy, 2006.
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  Abstract: There has been an advance in the social, political and corporate dialogue regarding global climate change (GCC) over the past twenty years. The question is: how much has the dialogue influenced corporate strategic action? Industry has learned to respond in a more positive manner to the socio-political dialogue concerning environmental issues, particularly global welfare issues. To distinguish increased dialogue from increased action, we examined 20 years of discussion in the utility industry's main trade journals, Utility Week and Electric Utility Week, looking for signs of strategic planning and action relating to GCC. We compare that dialogue to the types of strategic GCC activities taken by several randomly selected utility companies regarding GCC. Thus, if words are indeed turned into action, we would expect that there will be a positive correlation between reaching a critical mass in the journal discussion and greater strategic activity at the corporate level. If that is the case, it could be said that corporations are becoming more environmentally 'tuned-in' by incorporating socially important issues into their operations. They might also be said to be more politically positive regarding environmental issues, a change in strategy from the heretofore reactionary stance taken by most firms and industry associations.
• Fang, H., Liang, S., McClaran, M. P., J.D., W., Drake, S., Marsh, S. E., Thomson, A. M., Izaurralde, R. C., & Rosenberg, N. J. (2005). Biophysical characterization and management effects on semiarid rangeland observed from landsat ETM+ data. IEEE Transactions on Geoscience and Remote Sensing, 43(1), 125-133.
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  Abstract: Semiarid rangelands are very sensitive to global climatic change; studies of their biophysical attributes are crucial to understanding the dynamics of rangeland ecosystems under human disturbance. In the Santa Rita Experimental Range, AZ, the vegetation has changed considerably, and there have been many management activities applied. This study calculates seven surface variables: the enhanced vegetation index, the normalized difference vegetation index (NDVI), surface albedos (total shortwave, visible, and near-infrared), leaf area index (LAI), and the fraction of photosynthetically active radiation (FPAR) absorbed by green vegetation from the Enhanced Thematic Mapper (ETM+) data. Comparison with the Moderate Resolution Imaging Spectroradiometer vegetation index and albedo products indicates they agree well with our estimates from ETM+, while their LAI and FPAR are larger than from ETM+. Human disturbance has significantly changed the cover types and biophysical conditions. Statistical tests indicate that surface albedos increased and FPAR decreased following tree-cutting disturbances. The recovery will require more than 67 years and is about 50% complete within 40 years at the higher elevation. Grass cover, vegetation indexes, albedos, and LAI recovered from cutting faster at the higher elevation. Woody plants, vegetation indexes, and LAI have recovered to their original characteristics after 65 years at the lower elevation. More studies are needed to examine the spectral characteristics of different ground components.
• Biedenbender, S. H., Mcclaran, M. P., Quade, J., & Weltz, M. A. (2004).

  Landscape patterns of vegetation change indicated by soil carbon isotope composition

  . Geoderma, 119(1), 69-83. doi:10.1016/s0016-7061(03)00234-9
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  Vegetation change, particularly from the grass to shrub life form, is a critical issue on the world’s semiarid rangelands. Stable carbon isotope (y 13 C) values and associated radiocarbon ages from soil organic matter (SOM) were used to evaluate vegetation change across five landscape positions at a small enclosed basin in southeastern Arizona. Light and dense SOM fractions were separated to distinguish recent vegetation changes. The direction and timing of vegetation change differed with landscape position along a gentle elevation gradient from the basin outlet to a nearby volcanic ridge top. C4 perennial grasses have dominated the basin outlet, center, and toe slope landscape positions since at least 5000–6000 years BP, except for the dominance of C3 plants at the bottom of the outlet excavation at 5000 years BP. This isotopic change is associated with rounded cobbles that may have been a stream channel, suggesting the presence of C3 herbaceous or woody riparian vegetation. On midslope and ridge top landscape positions, where semidesert shrubs now dominate, the proportion of plants with C4 metabolism calculated from mass balance mixing formulas decreased from approximately 60% as recently as 400 years BP to only 1.5% observed today. The light SOM fraction from mid-slope and ridge top surface soil horizons was approximately 30% C4 and had a post-bomb date, suggesting that the conversion from grass to shrub occurred over the last several decades. D 2003 Elsevier B.V. All rights reserved.
• Cole, D. N., W., J., McClaran, M. P., Moore, P. E., & McDougald, N. K. (2004). Response of mountain meadows to grazing by recreational pack stock. Journal of Range Management, 57(2), 153-160.
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  Abstract: Effects of recreational pack stock grazing on mountain meadows in Yosemite National Park were assessed in a 5-year study. Yosemite is a designated wilderness, to be managed such that its natural conditions are preserved. Studies were conducted in 3 characteristic meadow types: shorthair sedge (Carex filifolia Nutt.), Brewer's reed grass (Calamagrostis breweri Thurber), and tufted hairgrass [Deschampsia cespitosa (L.) Beauv.]. Horses and mules grazed experimental plots at intensities of 15 to 69% utilization for 4 seasons. In all 3 meadows, grazing caused decreases in productivity. The mean reduction after 4 years of grazing was 18% in the shorthair sedge meadow, 17% in the Brewer's reed grass meadow, and 22% in the tufted hairgrass meadow. Grazing also caused shifts in basal groundcover (usually a reduction in vegetation cover and increase in bare soil cover), and changes in species composition. Productivity and vegetation cover decreased as percent utilization increased, while bare soil cover increased as utilization increased. Changes in species composition were less predictably related to differences in grazing intensity. Passive management of grazing is insufficient in wilderness areas that are regularly used by groups with recreational stock. Wilderness managers need to monitor meadow conditions and the grazing intensities that occur. Our study suggests that biomass and ground cover are more sensitive indicators of grazing impact than species composition. Managers must make decisions about maximum acceptable levels of grazing impact and then develop guidelines for maximum use levels, based on data such as ours that relates grazing intensity to meadow response.
• Fang, H., Liang, S., McClaran, M. P., J.D., W., Drake, S., Marsh, S. E., Thomson, A., Izaurralde, R. C., & Rosenberg, N. J. (2004). Deriving land surface biophysical parameters from satellite data for soil carbon sequenstration. International Geoscience and Remote Sensing Symposium (IGARSS), 6, 4277-4280.
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  Abstract: We apply a hybrid inversion algorithm to estimate land surface biophysical variables (e.g., leaf area index) from the CHRIS (Compact High Resolution Imaging Spectrometer), and ETM+. Field campaigns were conducted over Tucson, Arizona to validate the algorithms and the products. The derived products were compared for different human management activities. These products are then available for input to a plant growth model for calculating the potential for carbon sequestration.
• Hoppe, K. A., Amundson, R., Vavra, M., McClaran, M. P., & Anderson, D. L. (2004). Isotopic analysis of tooth enamel carbonate from modern North American feral horses: Implications for paleoenvironmental reconstructions. Palaeogeography, Palaeoclimatology, Palaeoecology, 203(3-4), 299-311.
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  Abstract: The accuracy of paleoenvironmental reconstructions based on isotope analyses of equid teeth is currently uncertain because the exact relationship between the isotope composition of modern feral equids and their environment has not been thoroughly studied. We analyzed the carbon and oxygen isotope values (δ13C and δ18O) of tooth enamel carbonate and the δ13C values of fecal samples from modern feral horses. We compared those values with the δ13C values of local vegetation and the δ18O values of local waters. Herds were studied in two contrasting localities: eastern Oregon, where grasslands consisted of 100% C3 species, and New Mexico, where >95% of the grasses were C4 species. Carbon isotope analyses of fecal material and tooth enamel suggest that horses consumed primarily grass, but some New Mexico horses also consumed significant amounts of shrubs and/or forbs. Microhistological analyses of fecal samples show that Oregon horses consumed 95% grass, and Oregon enamel δ13C values are consistent with a diet containing 100% C3 plants. Microhistological analyses of fecal samples from New Mexico indicate a diet averaging 75% grass, while enamel δ13C values suggest that diets averaged 85% C4 plants (range=72-97%). Thus, reconstructions of the C3/C4 ratio of grasses in ancient grasslands that are based on the δ 13C values of fossil equid teeth may underestimate the abundance of C4 grasses. The mean δ18O values of tooth enamel paralleled the trends observed in the mean δ18O values of precipitation. However, the mean δ18O values of enamel carbonate from Oregon and New Mexico differed by only 3.3‰, which is less than the difference in the mean δ18O values of precipitation (6.5‰). In addition, the range of δ18O values within New Mexico enamel samples (6.5‰) was greater than the difference between mean enamel δ18O values at each site. Calculated values for the δ18O of water ingested by horses are 2-3‰ more positive than mean δ18O values for corresponding precipitation, suggesting that horses consumed waters that were enriched in 18O due to evaporation. While our results confirm that local climatic and hydrological conditions can influence the δ 18O values of equid enamel, they also show that the δ 18O values of equid teeth are not always a direct proxy for the isotope ratios of precipitation. © 2003 Elsevier B.V. All rights reserved.
• Marsh, S. E., Mcclaran, M. P., Meko, D. M., & Skirvin, S. M. (2003).

  Climate spatial variability and data resolution in a semi-arid watershed, south-eastern Arizona

  . Journal of Arid Environments, 54(4), 667-686. doi:10.1006/jare.2002.1086
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  Abstract In the 10,000 km 2 San Pedro River watershed area in south-eastern Arizona, high-resolution spatial patterns of long-term precipitation and temperature were better reproduced by kriging climate data with elevation as external drift (KED) than by multiple linear regression on station location and elevation as judged by the spatial distribution of interpolation error. Mean errors were similar overall, and interpolation accuracy for both methods increased with increasing correlation between climate variables and elevation. Uncertainty in station locations had negligible effect on mean estimation error, although error for individual stations varied as much as 27%. Our future ability to examine spatial aspects of climate change at high spatial resolution will be severely limited by continuing closures of climate stations in this part of the United States.
• Angell, D. L., Mcclaran, M. P., & Wissler, C. (2002).

  Santa Rita Experimental Range digital database: user's guide

  . Southwest Research Station Bulletin, PSW-GTR-184. doi:10.2737/RMRS-GTR-100
• McClaran, M. P., Angell, D. L., & Wissler, C. (2002). Santa rita experimental range digital database: User's guide. USDA Forest Service - General Technical Report RMRS-GTR, 1-16.
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  Abstract: Long-term measurements and repeat photograph collections have been collected In a systematic manner on the approximately 21,000 ha Santa Rita Experimental Range (SRER) since Its establishment In 1903. This research facility, located In the Desert Grassland vegetation of southern Arizona, was administered by the U.S. Department of Agriculture until 1988, when it was transferred to the State of Arizona to be administered by the University of Arizona, College of Agriculture and Life Sciences. To facilitate the preservation of the long-term data collected on the SRER and to increase access to the data, we developed a digital archive that is accessible on the World Wide Web at http://ag.arizona.edu/SRER. The digital archive contains 10 databases, seven of which provide the longest records of ongoing measurements of precipitation, vegetation response to grazing and mesquite clearing experiments, and widespread photographic evidence of landscape changes available for the SRER. Two databases provide essential ancillary data about plant species names and spatial coverages (maps) of elevation, soils, plot locations, and other attributes. The final database is a digital version of a previously published annotated bibliography of SRER publications between 1903 and 1988. The information in these databases is available in five formats (ASCII text, Excel spreadsheet *.xls, ARCINFO *.e00, tagged image *.tif, and graphical interchange *.gif) that can be easily used in analytic, word processing, graphic, and geographic information system software.
• Angell, D. L., & McClaran, M. P. (2001). Long-term influences of livestock management and a non-native grass on grass dynamics in the Desert Grassland. Journal of Arid Environments, 49(3), 507-520.
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  Abstract: Density of 23 perennial grass species was measured in 25 permanent plots nine times between 1972-2000. Grass density was not related to the intensity of livestock grazing. Only one species expressed a difference between the summer rest and no summer rest with heavier stocking grazing treatments: bush muhly (Muhlenbergia porteri Scribn. ex Beal) density was less under the no summer rest with heavier stocking treatment. Beginning in 1975, the non-native Lehmann lovegrass (Eragrostis lehmanniana Nees) spread from distant seedings to one plot, and by 1991, it was the dominant species on most plots. The density of native species was not related to the length of time that the non-native lovegrass was present on a plot. In general, native species declined prior to the arrival and increase of the non-native lovegrass. © 2001 Academic Press.
• Brunson, M. W., Huntsinger, L., & Mcclaran, M. P. (2001).

  Future Social Changes and the Rangeland Manager

  . Rangelands, 23(6). doi:10.2458/azu_rangelands_v23i6_mcclaran
• Brunson, M. W., Huntsinger, L., & Mcclaran, M. P. (2001).

  Future social changes and the rangeland manager.

  . Rangelands, 23(6), 33-35.
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  Editor's Note: The International Affairs Committee sponsored a symposium entitled "Rangeland Professionals and Society: Future Directions" at the 2001 annual SRM meeting in Kona, Hawaii. From those presentations, a series of articles is being published in Rangelands highlighting perspectives on rangelands from around the world. The editors and authors wish to thank Dow AgroSciences of Indianapolis, Indiana, for a grant made in support of the symposium.
• Coronado-Quintana, J., & McClaran, M. P. (2001). Range condition, tenure, management, and bio-phyiscal relationships in Sonora, Mexico. Journal of Range Management, 54(1), 31-38.
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  Abstract: The objective of this study was to describe the relationship among range condition scores, tenure system, management practices and bio-physical variables for 107 communal ejido ranches and 373 private ranches in Sonora, Mexico. The data was obtained from assessments of range condition and recommended carrying capacity for individual ranch units that were completed between 1973 and 1993 by the Comisión Técnica para la Determinación de Coeficientes de Agostadero. Variables measured were range condition, land tenure (communal ejido or private ranch), management characteristics (human density, livestock stocking rate, ranch size, and infrastructure condition), and bio-physical characteristics (rangeland site quality and precipitation in the year of assessment). We used a combination of simple, univariate chi-square analyses and more complex, multivariate ordered logistic regression analyses to assess the relationships among these variables. There was no evidence from the logistic regression analysis that range condition of ranches in Sonora was related to the ejido or private tenure systems. Infrastructure condition was different between the 2 tenure systems, and infrastructure condition was positively related to range condition for both ejido and private ranches. Based on the univariate and multivariate analyses, precipitation amounts in the year of assessment was less for private ranches, and range condition on private ranches was more sensitive to precipitation than ejido ranches. Compared to estimates made in the 1960's and 1970's in other parts of Mexico, we found there to be less of a difference in stocking rate between the more lightly stocked private ranches and more heavily stocked ejido ranches, and generally good condition infrastructure on all ranches. The important relationship between precipitation and range condition implies that range condition assessments should be done over many years to produce estimates of trend that can be compared across wet and dry years.
• Kuehl, R. O., McClaran, M. P., & Zee, J. V. (2001). Detecting fragmentation of cover in desert grasslands using line intercept. Journal of Range Management, 54(1), 61-66.
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  Abstract: Changes in the amount or spatial distribution of grass plants are thought to be indicative of the stability of desert grasslands. This study assessed, through simulation, the sensitivity of statistical properties for distance between plants (fetch length), measured with a line intercept transect, to changes in the spatial distribution and amount of plant cover. Monitoring plots, 30 × 30 m, were simulated for 1, 2.5, 5, 10 and 15% grass cover with random and fragmented spatial distribution. Fetch lengths were measured on 2 randomly placed 30 m transects. In addition to the median and interquartile range, the asymmetry of the sampling distributions was measured with a ratio [(maximum-median)/(median-minimum)] that would identify the presence of at least 1 large open space. The accuracy of the fetch length method was confirmed by the similarity of its sampling distribution to that for the well known random point-to-plant sampling procedure. In both the fetch length and the point-to-plant measures, the median and interquartile range increased with decreasing cover for random and fragmented distribution. The asymmetry estimate increased sharply with increasing cover for the fragmented distribution but asymmetry was nearly constant with increasing cover for the random distribution. The results suggest that the evaluation of changes over time at a monitoring site could use fetch lengths measured along a line intercept transect to detect changes in both absolute and spatial arrangement of cover.
• McClaran, M. P. (2000). Viewpoint: Selecting the 5 most important papers in the first 50 years of the journal of range management. Journal of Range Management, 53(3), 250-254.
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  Abstract: A graduate seminar to select the 5 most important papers published in the first 50 years of the Journal of Range Management (JRM), 1948-1997, cultivated an appreciation for the development of the discipline of rangeland science and management, and provided some historical perspective to judge the JRM. A review of textbooks, and papers describing early milestones and the use of citation counting were helpful in developing criteria to discriminate the importance of papers. The greatest disagreement among the 9 participants focused on the use of citation counts as a criterion: 2 students used only counts and 3 students refused to use counts. Eighteen papers received at least 1 vote as a top 5 paper, and 2 plant succession-vegetation monitoring papers were clearly the most popular. The exercise revealed that discontent with the JRM is not new. Although the JRM now covers a wider variety of topics, including both reductionist and synthetic works, some students felt that it was less encompassing of multiple values of rangelands and the breadth of rangeland science than recent texts. The students found that the selection of important papers expanded their understanding of the discipline and their resolve to publish in the JRM. Ideally, others will be challenged to perform this review for the benefit of students, the discipline, and the JRM.
• McClaran, M. P., & Umlauf, M. (2000). Desert grassland dynamics estimated from carbon isotopes in grass phytoliths and soil organic matter. Journal of Vegetation Science, 11(1), 71-76.
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  Abstract: We document the potential for using carbon isotopes in both soil organic matter (SOM) and grass phytoliths in soil to increase the temporal and taxonomic resolutions of long term vegetation dynamics. Carbon isotope values from both SOM and phytoliths are expected to describe both the age of material through 14C dating, and the photosynthetic pathway of the source plant material through ratios of 12C/13C. Taxonomic resolution is increased because the phytoliths examined are specific to grasses, whereas the SOM reflects the contribution of all the vegetation. Temporal resolution is increased because phytoliths are less mobile in the soil profile than SOM, and can therefore provide older dates from the same soil depth. Our results, from a desert grassland site in southwestern North America, largely confirm these expectations, and show that C4 species have dominated the grass composition for the last 8000 yr, C3 non-grass vegetation increased about 100-350 yr BP, and no significant C3 grass or non-grass vegetation existed between 350-2000 yr BP.
• Mcclaran, M. P. (2000).

  History of the Range Curriculum: Are There New Trails?

  . Rangelands Archives, 22(6), 23-27. doi:10.2458/azu_rangelands_v22i6_mcclaran
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  History of the range curriculum: are there new trails? DOI:10.2458/azu_rangelands_v22i6_mcclaran
• McClaran, M. P., & King, D. A. (1999). Procedural fairness, personal benefits, agency expertise, and planning participants' support for the forest service. Natural Resources Journal, 39(3), 441-453.
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  Abstract: Numerous appeals of Forest Plans have been interpreted as a lack of support for the Forest Service. Questionnaire responses from 455 Forest Plan participants show that agency support was more strongly related to perceptions of procedural fairness and personal benefits than to agency expertise expressed as information about resources and human needs. These responses suggest that agency support will be most sensitive to changing perceptions of procedures from somewhat unfair to somewhat fair, and preventing reductions in personal benefits. Furthermore, perceptions of fair procedures were half as frequent when benefits were expected to decline than when they were expected to either increase or not change.
• Moote, M. A., & Mcclaran, M. P. (1997). Viewpoint: Implications of participatory democracy for public land planning. Journal of Range Management, 50(5), 473-481.
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  Abstract: Non-traditional, collaborative public participation approaches such as coordinated resource management have been proposed to improve the public participation process used in public land planning on rangelands. Either implicitly or explicitly, most advocates of such non-traditional approaches to public participation seem to embrace s participatory democracy model of governance. Whether or not this model for decision-making can practicably be implemented, given our current institutional and legal frameworks for public lands management, has not been closely examined. Criticisms of the traditional public participation process are categorized into 5 main issues: efficacy; representation and access; information exchange and learning; continuity of participation; and decision-making authority. We use these categories to evaluate the feasibility of implementing participatory democracy-based decision-making in public lands planning. Although there is some statutory and regulatory authority for participatory democracy in public land planning, there are a number of logistical, legal, and even philosophical challenges to its application that warrant further consideration.
• Moote, M. A., McClaran, M. P., & Chickering, D. K. (1997). Theory in practice: Applying participatory democracy theory to public land planning. Environmental Management, 21(6), 877-889.
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  Abstract: Application of participatory democracy theory to public participation in public land planning, while widely advocated, has not been closely examined. A case study is used here to explicate the application of participatory democracy concepts to public participation in public land planning and decision making. In this case, a Bureau of Land Management resource area manager decided to make a significant shift from the traditional public involvement process to a more participatory method-coordinated resource management (CRM). This case was assessed using document analysis, direct observation of CRM meetings, questionnaires, and interviews of key participants. These sources were used to examine the CRM case using participatory democracy concepts of efficacy, access and representation, continuous participation throughout planning, information exchange and learning, and decision-making authority. The case study suggests that social deliberation in itself does not ensure successful collaboration and that establishing rules of operation and decision making within the group is critical. Furthermore, conflicts between the concept of shared decision- making authority and the public land management agencies' accountability to Congress, the President, and the courts need further consideration.
• McClaran, M. P. (1995). Desert grasslands and grasses. The desert grassland, 1-30.
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  Abstract: Desert grasslands experience hot, dry, sunny climates, and have one of the lowest levels of primary production and rates of solar energy conversion of North American grassland types. Peak growth occurs later than in these other grassland types, coincident with the rainfall maximum during June-September. Reflecting this late-season growth the proportion of C4 grasses is greater than that found in other grasslands of this continent. Shrubs and trees can be abundant but the relative proportion of grasses and shrubs has changed greatly during this century. Habitat fragmentation and the impact of introduced species are the major human environmental impacts. Members of the grass family (Poaceae) are important because of their morphological and physiological adaptations to withstand constant defoliation; regrowth ability depends on severity and season of grazing. Recruitment is from seeds, rhizomes or stolons. Desert grasses are relatively short-lived, though maximum longevity can be several decades; the influence of weather and defoliation varies among species.
• McClaran, M. P., & McPherson, G. R. (1995). Can soil organic carbon isotopes be used to describe grass-tree dynamics at a savanna-grassland ecotone and within the savanna?. Journal of Vegetation Science, 6(6), 857-862.
• Brady, W. W., & Mcclaran, M. P. (1994).

  Arizona'a diverse vegetation and contributions to plant ecology.

  . Rangelands Archives, 16(5), 208-217.
  More info

  In the 1880's, Mr. and Mrs. J.C. Lemmon were among the few botanists to collect plants in Arizona during the conflict between Apaches and European settlers. Unlike many settlers, the Lemmon's traveled safely. Apparently the Apaches considered plant collecting a form of insanity (Benson 1959). Many have continued collecting plants and studying vegetation in the groundbreaking and unyielding tradition of the Lemmons. These subsequent contributions have been at the forefront of plant ecology, and their legacy spreads well beyond the state borders. Arizona extends over 7 million acres between 31 and 360 north latitude, and about 80% of the area is state or federal public land. The climate is generally arid, with a bimodal precipitation pattern of wet summer months (JulySeptember), moderately moist winter months (December-March) and a very hot and dry spring and early summer (Green and Sellers 1964). The proportion of winter precipitation increases to the north. Additionally, dramatic elevational gradients in Arizona alter the magnitude of the temperature and precipitation values. This elevational gradient ranges from 68 feet near the Colorado River in southwest to over 12,630 feet on Humphery Peak in the north. The Mogollon Rim is a 1,6002,300 foot escarpment that rises above the central desert regions. Rising above the Rim to greater than 9,800 feet are the White Mountains to the east, and San Francisco Mountains to the north. In the southeast, a basin and range physiography dominates the landscape with valleys
• McClaran, M. P., & Cole, D. N. (1993). Packstock in wilderness: use, impacts, monitoring, and management. General Technical Report - US Department of Agriculture, Forest Service.
  More info

  Abstract: Sections describe: the amount and composition of packstock use in wilderness, impacts associated with packstock use, methods for monitoring impacts caused by packstock, techniques for managing packstock in wilderness, examples of packstock management programs, and research needs. -from Authors
• Mcclaran, M. P., & Sundt, P. C. (1993).

  The Binomial Use Monitoring (BUM) Method for Desert Shrubs

  . Rangelands Archives, 15(5), 224-227.
• Anable, M. E., & Mcclaran, M. P. (1992).

  SPREAD OF INTRODUCED LEHMANN LOVEGRASS ALONG A GRAZING INTENSITY GRADIENT

  . Journal of Applied Ecology, 29(1), 92-98. doi:10.2307/2404352
  More info

  1. Changes in density of Lehmann lovegrass and native grasses, and the proportion of lovegrass present along a livestock grazing intensity gradient were measured on six occasions in permanent plots during 1972-90, on the Santa Rita Experimental Range, Arizona, USA. The gradient included grazing exclosures and plots radiating away from a cattle watering point. Lehmann lovegrass spread from sowings done during 1945-59 4km from the water point and an average 1 8 km from the exclosures. 2. Lovegrass density increased with time but was not affected by different grazing intensities. Native grass density decreased, and lovegrass relative abundance increased with time and as grazing intensity increased. Lovegrass density and relative abundance did not differ between adjacent ungrazed and grazed areas. 3. Livestock grazing was not necessary for Lehmann lovegrass to spread, but the lovegrass relative abundance was greater at higher grazing intensities.
• Anable, M. E., Mcclaran, M. P., & Ruyle, G. B. (1992).

  Spread of introduced Lehmann lovegrass Eragrostis lehmanniana Nees. in Southern Arizona, USA

  . Biological Conservation, 61(3), 181-188. doi:10.1016/0006-3207(92)91114-8
  More info

  Abstract Through seeding and subsequent spread, Lehmann lovegrass Eragrostis lehmanniana Nees. has transformed the structure and function of at least 145 000 ha of semi-desert grassland in southern Arizona since its introduction in 1932. Our study of its spread on the Santa Rita Experimental Range since 1954 showed that by 1989 it was present on >85% of 75 relatively widely dispersed non-seeded permanent plots and accounted for >40% of all perennial grass plants on these plots. In addition, it represented >50% of the perennial grass plants on sites 90% of the grass biomass and produce 2–4 times more biomass annually than native grass vegetation. In the future, strong consideration of these plant composition changes, and the likely decrease in wildlife diversity and increase in fire frequencies accompanying Lehmann lovegrass dominance, should be made before seeding the species.
• Bartolome, J. W., & McClaran, M. P. (1992). Composition and production of California oak savanna seasonally grazed by sheep. Journal of Range Management, 45(1), 103-107.
  More info

  Abstract: Tested the effects of two seasonal grazing strategies on within- and between-year production and composition in blue oak Quercus douglasii savanna understory and adjacent open annual grassland. Moderate intensity summer-fall-winter and spring-summer sheep use had few within-year effects. Production and composition varied considerably between years in both treatments. Forbs (especially legumes) decreased in open grassland and oak understory between years within both seasonal grazing regimes. This change could not have been caused by selective grazing because there were no corresponding within-year patterns. Instead, between-year changes are more likely related to nonselective effects of stocking rate and/or weather. -from Authors
• McClaran, M. P., & Anable, M. E. (1992). Spread of introduced Lehmann lovegrass along a grazing intensity gradient. Journal of Applied Ecology, 29(1), 92-98.
  More info

  Abstract: Changes in density of Eragrostis lehmanniana and native grasses, and the proportion of lovegrass present along a livestock grazing intensity gradient were measured, on the Santa Rita Experimental Range, Arizona. The gradient included grazing exclosures and plots radiating away from a cattle watering point. Lehmann lovegrass spread from sowings 4 km from the water point and an average 1.8 km from the exclosures. Lovegrass density increased with time but was not affected by different grazing intensities. Native grass density decreased, and lovegrass relative abundance increased with time and as grazing intensity increased. Livestock grazing was not necessary for Lehmann lovegrass to spread, but the lovegrass relative abundance was greater at higher grazing intensities. -from Authors
• Mcclaran, M. P., & Sundt, P. C. (1992).

  Population dynamics of the rare orchid, Spiranthes delitescens.

  . Southwestern Naturalist, 37(3), 299-303. doi:10.2307/3671873
• McClaran, M. P. (1991). Forest Service and livestock permittee behavior in relation to wilderness designation. Journal of Range Management, 44(5), 483-486.
  More info

  Abstract: The effect of wilderness designation, during the first 20 yr after designation, on Forest Service and permittee behavior on Coronado and Tonto National Forests in Arizona was evaluated. In general, permitted animal unit months increased on wilderness allotments but remained the same for nonwilderness allotments, but there was no difference on Coronado National Forest when forests were analyzed separately. -from Author
• Mcclaran, M. P., & Moore, S. D. (1991).

  Symbolic dimensions of the packstock debate

  . Leisure Sciences, 13(3), 221-237. doi:10.1080/01490409109513139
  More info

  Abstract The use of pack animals to transport people and equipment into wilderness has become increasingly controversial. Advocates of greater packstock restriction point to evidence of ecological and sociological impacts. Packstock supporters defend the traditional role of packstock in wilderness and call for greater self‐regulation. This article proposes that the conflict results from the clash of three symbolic realms of belief: (1) wilderness as a sacred object; (2) arguments against packstock derived from an ecologistic ordering of wilderness; and (3) a cognitive ordering of the conflict that allows moral pain to be felt on both sides. Three hypotheses about wilderness managers’ attitudes toward symbolic statements were proposed and tested by using univariate statistics and bivariate and multivariate logistic analysis. The results indicate strong support for wilderness symbolism and less strong support for packstock symbolism. Numbers of packstock trips, Government Service grade, number of years in t...
• Amy, D. J., Dixon, K., Mcclaran, M. P., & Wondolleck, J. M. (1990).

  The Politics of Environmental Mediation 1987

  . Journal of Range Management, 43(3), 277. doi:10.2307/3898692
• McClaran, M. P. (1990). Livestock in wilderness: A review and forecast. Environmental Law, 20(4), 857-889.
• McClaran, M. P., & Bartolome, J. W. (1990). Comparison of actual and predicted blue oak age structures. Journal of Range Management, 43(1), 61-63.
  More info

  Abstract: Examined the role of management on the current lack of Quercus douglasii recruitment on California foothill rangelands. Diameter at breast height accounted for 42-71% of the variation in tree age at 2 sites. Actual age structures were significantly different than age structures predicted from all regression equations at both sites. Use of age structures to infer the role of management on blue oak population dynamics requires direct age measurement. -from Authors
• McClaran, M. P., & Bartolome, J. W. (1989). Fire-related recruitment in stagnant Quercus douglasii populations. Canadian Journal of Forest Research, 19(5), 580-585.
  More info

  Abstract: Age structure, stem analysis and fire-scar history from >500 blue oak individuals on 2 sites in central California revealed: 1) meager tree recruitment since the 1940s and few trees older than 150 yr; 2) increased fire frequency following Anglo-American settlement in 1848 until fire suppression efforts in the 1940s; 3) a positive association between tree ages and fire dates; and 4) superior vertical growth to 135 cm of postfire sprouts (trees with ground-level ages within 1 yr after fires) on the site with less livestock browsing pressure. The association between tree ages and fire dates may have resulted from temporal concentration of postfire seedling sprouts, and faster vertical growth of postfire sprouts compared with true seedlings. However, sampling from existing trees may dampen the difference in vertical growth rates between sprouts and true seedlings where there is heavy browsing, because only true seedlings that grew as fast as sprouts survived and were available for sampling. -from Authors
• Mcclaran, M. P. (1989).

  Recreational pack stock management in Sequoia and Kings Canyon National Parks.

  . Rangelands Archives, 9(1), 3-8.
  More info

  HORSES, MULES, BURROS, AND RECENTLY llamas and goats, are used to transport visitors and their supplies to backcountry and wilderness areas in the western United States. These animals were so synonymous with backcountry travel that Aldo Leopold (1921) defined the minimum size of wilderness area as a continuous stretch of country big enough to absorb a 2-week trip with pack stock. Although pack stock use has declined in the past 30 years, approximately 1 1% of all visitors use stock when visiting wilderness areas (Washburne and Cole 1983). Of particular interest to resource managers is the status of pack stock management in these backcountry areas. The history of pack stock use and management in Sequoia and Kings Canyon National Parks provides an excellent case study to evaluate the application of traditional range management principles in a non-traditional, recreation setting. Sequoia National Park was established in 1890 to protect the magnificent groves of giant Sequoia trees (Sequoiadendron gigantea), and expanded to its current boundaries in 1926. Initially, Kings Canyon National Park was withdrawn from the public domain as part of the Forest Reserve System in 1891, and in 1940 was transferred to the National Park Service. Although legally separate parks, their proximity logically led to joint administration (Fig. 1). Located in the southern Sierra Nevada, the parks encompass over 850,000 acres, of which 85% is part of the National Wilderness Preservation System. Both parks are also part of the United Nations Man and the Biosphere Programme's International Biosphere Reserve network of outstanding protected samples of the world's major ecosystems. Backcountry elevations range from 2,000 ft to 14,495 ft at the crest of Mt. Whitney, the highest point in conterminous United States. Topography varies from U-shaped glacial valleys with steep, sheer walls, to subalpine tablelands perched above these valleys, and massive jumbles of house-sized granite boulders and jagged spires that pierce the passing clouds. Plant communities vary from oak woodland and chaparral at lower elevations; mixed conifer and giant Sequoia
• McClaran, M. P. (1988). Comparison of fire history estimates between open-scarred and intact Quercus douglasii. American Midland Naturalist, 120(2), 432-435.
  More info

  Abstract: Fire scars in 181 scarred Quercus douglasii cross sections were dated from 2 different stands in the Sierra Nevada foothills, California. In the stand with no fires for the last 35 yr, open-scarred trees revealed a shorter fire history, 90% fewer fire dates, and a mean fire interval (MFI) that was shorter than determined from intact trees. In the stand with no fires for the last 15 yr, MFI and length and length of record were comparable but open-scarred trees accounted for 27% fewer fires than intact trees. Open-scarred trees were twice as likely to scar as intact trees, but the average number of scars tree-1 were similar. Time since last fire is critical, as scars may heal before sampling. This suggests that fire history estimates will be most affected by sample restriction in areas with long periods of fire suppression. -from Author
• Bartolome, J. W., & Mcclaran, M. P. (1985).

  The Importance of Oak to Ranchers in the California Foothill Woodland

  . Rangelands Archives, 7(4), 158-161.
• McClaran, M. P., Romm, J., & Bartolome, J. W. (1985). Differential farmland assessment and land use planning relationships in Tulare County, California.. Journal of Soil & Water Conservation, 40(2), 252-255.
  More info

  Abstract: Research has shown that participation in California's differential assessment program, the California Land Conservation Act (CLCA), at the rural-urban fringe is limited by landowners' 'unreasonable expectations about development'. Integration of land use planning and the CLCA has been proposed to increase participation by presenting reasonable expectations.-from Authors

Proceedings Publications

• Mcclaran, M. P. (2000).

  Improving livestock management in wilderness.

  . In ). Wilderness science in a time of change – Conference. Volume 5: Wilderness Ecosystems, Threats, and Management., RMRS-P-15 VOL-5, 49-63.
  More info

  Recreation livestock (horses, mules, llamas, and goats) use accounts for 11% of all wilderness visits, and production live- stock (cattle and sheep) use occurs in 37% of all wilderness areas. Recreation use is expected to increase at the same rate as total wilderness use, but production use will change little. Managers should recognize that the relationship between the severity of impacts and the intensity of livestock use can be linear or curvilin- ear because different management approaches will be effective for each type of relationship. Improved livestock management will occur with greater coordination of knowledge and staff in range and wilderness management. Recreation and production livestock in wilderness are authorized under different provisions in the Wilderness Act, and distinct tools and criteria are prescribed to manage their impacts. Recreation livestock use conforms to the recre- ational mission of the Act and is subject to full discretionary interpretation by agencies to manage that use within levels consistent with a goal of maintaining the wilderness charac- ter of an area. In contrast, production livestock use is one of five uses (mining, aircraft & motorboats, control of fire, disease & insects, water resources facilities, and livestock grazing) that were granted special status to continue in wilderness if they existed prior to designation. Further, some provisions for production livestock management ex- plicitly ignore the wilderness character goal of an area, leaving little room for discretionary interpretation by the agencies.
• Moore, P. E., Cole, D. N., Wagtendonk, J. W., Wagtendonk, J. W., Mcclaran, M. P., & Mcdougald, N. (2000).

  Meadow Response to Pack Stock Grazing in the Yosemite Wilderness: Integrating Research and Management

  . In Wilderness science in a time of change, RMRS-P-15 VOL-5, 160-164.
  More info

  Management decisions on meadow preservation and allowable use are, ideally, based on scientific information that describes the relationship between levels of impact and levels of use. This information allows managers to provide the best protection of meadow systems while responding to demands for recreational use of mountain meadows. Monitoring and research activities can be coordinated to support management by gathering information on measurable levels of meadow use, meadow response to different levels of use and cause and effect relationships reflected in meadow response. Based on this information, wilderness managers can decide on the maximum acceptable impacts to meadows that still provide protection. Meadows occupy less than 10 percent of the montane and subalpine regions of the Sierra Nevada, yet they support disproportionate amounts of biological diversity, ecosystem function and aesthetic interest. They contain high plant diversity, provide wildlife forage and habitat, filter organic inputs to streams and, from a human perspective, provide high aesthetic value. They have long been valued as well for livestock and pack stock forage that lasts late into the

Presentations

• Eitzel, M., Rodriguez-Burtitica, S., Harpole, W., Aicher, R., Larios, L., Mcclaran, M. P., & Suding, K. (2022, October). Reproduction and Recruitment of Blue Oak in the Sierra Nevada Foothills of California. . Eighth Symposium on Oak Woodlands: Sustaining Oak Woodlands Under Current and Future Conditions. San Luis Obispo, CA: University of California, Cooperative Extension.
• Mcclaran, M. P. (2022, JANUARY). Santa Rita Experimental Range Long-term data and major accomplishments.. Arizona Section Society for Range Management Annual Meeting. Virtual.
• Gillan, J., Mcclaran, M. P., Swetnam, T., Heilman, P., Noelle, S., & Turner, R. (2018, February). Estimating forage biomass and utilization in a desert grassland with small unmanned aerial system imagery. 71st Annual Meeting, Society for Range Management. Sparks, NV: Society for Range Management.
• Gornish, E., & Mcclaran, M. P. (2018, January). Grassland and mesquite on the Santa Rita Experimental Range: An historical perspective. Altar Valley Conservation Alliance Brush Management Workshop.
• Gornish, E., & Mcclaran, M. P. (2018, May). Relationships between grass and mesquite cover based on long-term data: Implications for restoration opportunities. Madrean Conference. Tucson, AZ.
• Gornish, E., & Mcclaran, M. P. (2018, October). Relationships between grass and mesquite cover based on long-term data: Implications for restoration opportunities. Society for Ecological Restoration Southwest Chapter. Flagstaff, AZ.
• Landreville, K., & Mcclaran, M. P. (2018, February). Guide to Increasing Drought Preparation. Farm Home Ranch Day, Graham County Cooperative Extension. Safford, AZ: Graham County Cooperative Extension.
• Mcclaran, M. P. (2018, February). Overview: Weather and Climate Trends in Our Region. Farm Home Ranch Day, Graham County Cooperative Extension. Safford, AZ: Grahamn County Cooperative Extension.
• Mcclaran, M. P. (2018, February). Standardized Precipitation Index Explorer. Farm Home Ranch Day, Graham County Cooperative Extension. Safford, AZ: Graham County Cooperative Extension.
• Mcclaran, M. P. (2018, February). Weather, Drought and Tools to Help. Arizona Cattle Growers Association Winter Meeting. Phoenix, AZ: Arizona Cattle Growers Association.
• Mcclaran, M. P. (2018, September). Three lessons from drought planning to help plan for climate change. 20th Meeting United Nations FAO-CIHEAM (International Centre for Advanced Mediterranean Agronomic Studies) Mountain Pasture Network. Ballstad, Norway: United Nations FAO-CIHEAM (International Centre for Advanced Mediterranean Agronomic Studies) Mountain Pasture Network.
• Mcclaran, M. P. (2017, Fall). Review of Collaborative Drought Preparation for Forest Service Grazing Allotments.. Region 3 National Forest Range and Wildlife Managers Annual Meeting. Albuquerque, NM: US Forest Service.
• Mcclaran, M. P. (2017, Fall). Standardized Precipitation Index Explorer Tool. Region 3 National Forest Range and Wildlife Managers Annual Meeting.. Albuquerque, NM: US Forest Service.
• Mcclaran, M. P. (2017, Spring). Review of Collaborative Drought Preparation for Forest Service Grazing Allotments.. Annual Meeting. Tucson, AZ: Arizona Section Society for Range Management.
• Mcclaran, M. P. (2017, Spring). Standardized Precipitation Index Explorer Tool.. Annual Meeting. Tucson, AZ: Arizona Section Society for Range Management.
• Mcclaran, M. P. (2017, summer). Livestock Management and Drought Planning Workshop. Coronado National Forest Grazing Permittee Annual Meeting.. Sonoita, AZ: Coronado Natioanl Forest.
• Mcclaran, M. P. (2017, summer). Standardized Precipitation Index Explorer Tool.. Cattlemens College. Prescott, AZ: Arizona Cattle Growers Association.
• Mcclaran, M. P. (2017, summer). Standardized Precipitation Index Explorer Tool.. Coronado National Forest Grazing Permittee Annual Meeting.. Sonoita, AZ: Coronado National Forest.
• Mcclaran, M. P., Hawkes, K., & Crimmins, M. A. (2017, Summer). Collaborative Drought Preparation Project Review.. Cattlemens College. Prescott: Arizona Cattle Growers Association.
• Mcclaran, M. P. (2016, Fall). How to Select and Complete Research.. Teacher Outreach and Training Workshop. Santa Rita Experimental Range, AZ: University of Arizona CALS Cooperative Extension.
• Mcclaran, M. P. (2016, Fall). Planning as a prerequisite to using drought information.. Intermountain West Drought Early Warning System Drought and Climate Outlook.. Oracle, AZ: National Integrated Drought Information System and National Oceanic and Atmospheric Administration.
• Mcclaran, M. P. (2016, Fall). Planning as a prerequisite to using drought information. Winter Season Outlook and Impacts Forum. Las Cruces, NM: National Integrated Drought Information System, USDA Southwest Climate Hub and National Drought Mitigation Center.
• Mcclaran, M. P. (2016, Spring). Santa Rita Experimental Range and National Ecological Observatory Network.. UA Arid Lands III. UA Global Initiatives.. University of Arizona: UA Global Initiatives.
• Brugger, J., Mcclaran, M. P., & Sprinkle, J. E. (2015, November). The Co-Production of Natural Resources Use on US Public Lands. American Anthropological Association Annual Meeting.
• Mcclaran, M. P. (2015, October). Protective Motivation Theory Applied to Ranchers in the Southwest. Social Science Methods in Climate Adaptation.
• Mcclaran, M. P. (2013, summer). Drought on rangelands: Considering scales of space and time.. Development of Real-World Drought Management Scenarios for Arizona Rangelands.. Cottonwood, AZ: University of Arizona.
• Mcclaran, M. P. (2013, summer). Future of Livestock Production in the Southwest in the Face of Climate and Economic Uncertainty: Range Scientist Perspective.. Future of Meat Production, Processing & Local Distribution in Pima County, Southeastern Arizona.. Tucson, AZ: Pima County.
• Mcclaran, M. P., & Wei, H. (2013, December). Recent drought phase in a 73-year record viewed at two spatial scales: Implications for livestock production on rangelands in the Southwest.. USDA-ARS Southwest Watershed Research Center Seminar Series. Tucson, AZ: USDA-ARS Southwest Watershed Research Center.
• Mcclaran, M. P., Guertin, D. P., Ruyle, G. B., Wei, H., Dalke, A., Butler, G., & Ross, M. (2013, summer). Grazing Land Conservation Practices and Drought on Southwestern Rangelands. CEAP Rangeland Assessment Symposium. Reno, NV: Soil and Water Conservation Society.

Poster Presentations

• Anselmetto, N., Nota, G., Gorlier, A., & Mcclaran, M. P. (2022, November). Differences in population size structure drive grass response to long-term livestock removal.. 18th Symposium on Research Insights in Semi-arid Environments (RISE). Tucson, Az.
• Mcclaran, M. P., Ponce-Campos, G., Heilman, P., & Gillan, J. (2022, December). Using UAV and Satellite-based Sensing to Detect Eroded Ecological States at the Landscape Scale.
  . American Geophysical Union Fall Meeting. San Franciso, CA.
• Ponce-Campos, G., Mcclaran, M. P., Heilman, P., & Gillan, J. (2022, November). Using UAV and Satelitte-based sensing to detect eroded ecological states at the landscape scale. 18th Symposium on Research Insights in Semi-arid Environments (RISE). Tucson, AZ.
• Crimmins, M. A., Hall, A. L., Brischke, A. S., Grace, J. L., Mcreynolds, K. H., & Mcclaran, M. P. (2019, August). Rangeland Precipitation Monitoring Training Program for Ranchers and Land Managers. University of Arizona Cooperative Extension Annual Conference. Tucson, AZ: University of Arizona Cooperative Extension.
• Crimmins, M. A., Mcclaran, M. P., & Hawkes-Landerville, K. (2018, February). Filling in the Gaps: Managing and Interpreting Site-Specific Precipitation Observations with the myRAINge Log Tool. 71st Annual Meeting Society for Range Management. Sparks, NV: Society for Range Management.
• Hall, A. L., Crimmins, M. A., & Mcclaran, M. P. (2018, July). Integrating Climate Data with Rangeland Monitoring to Improve Ranch-Scale Drought Detection. National Association of County Agriculture Agents Conference. Chattanooga, TN: National Association of County Agriculture Agents.
• Hawkes, K., Mcclaran, M. P., & Crimmins, M. A. (2018, February). Guide to Co-Developing Drought Preparation Plans for Livestock Grazing on SW National Forests. 71st Annual Meeting, Society for Range Management. Sparks, NV: Society for Range Management.
• Mcclaran, M. P., Crimmins, M. A., & Hawkes, K. (2018, February). Talking About Drought: SPI Explorer Tool Builds a Common Language. 71st Annual Meeting, Society for Range Management,. Sparks, NV: Society for Range Management.
• Bagchi, S., Singh, N., Bestelmeyer, B., Mcclaran, M. P., Briske, D., & Murty, K. (2017, Spring). Quantifying plant community dynamics using animal movement models-implications for ecosystem resilience.. Gordon Research Conference on Movement Ecology of Animals. Ventura, CA: Gordon Research Center.
• Brischke, A. S., Mcclaran, M. P., Crimmins, M. A., & Hall, A. L. (2017, October). Developing Resources to Help Ranchers Plan for Drought in Arizona. National Association of County Agriculture Agents Western Region Professional Improvement Conference. Albuquerque, NM: NACAA Western Region.
• Gallery, R. E., Mcclaran, M. P., & Kariuki, S. (2017, Summer). How does recreational camping affect cover-mediated soil microbial activity?. Soil Ecology Society Biennial Meeting. Ft Collins, CO: SoilEcology Society.
• Gillan, J., Mcclaran, M. P., Swetnam, T., Heilman, P., & Turner, R. (2017, Fall). Estimating forage utilization with unmanned aerial imagery. RISE (Research Insights in Semi-arid Ecosystems) Symposium. Tucson, AZ: CALS and USDA ARS.
• Kariuki, S., Mcclaran, M. P., & Gallery, R. E. (2017, Fall). How does recreational camping affect cover-mediated soil microbial activity?. RISE (Research Insights in Semi-arid Ecosystems) Syposium. Tucson, AZ: CALS and USDA ARS.
• Kariuki, S., Mcclaran, M. P., & Gallery, R. E. (2017, Summer). How does recreational camping affect cover-mediated soil microbial activity?. Biennial Meeting. Ft Collins, CO: SoilEcology Society.
• Hawkes, K., Mcclaran, M. P., Brugger, J., Crimmins, M. A., Howery, L. D., Ruyle, G. B., Sprinkle, J. E., & Tolleson, D. (2016, October). Using an Interactive Scenario-Planning Tool for Ranchers and Forest Service to Prepare for Drought. 13th RISE Symposium (Research Insights in Semi-arid Environments. Tucson, AZ: College of Agriculture and Life Science.
• Hawkes, K., Mcclaran, M. P., Brugger, J., Crimmins, M. A., Howery, L. D., Ruyle, G. B., Sprinkle, J. E., & Tolleson, D. (2016, winter). Using a co-development process to improve livestock grazing during drought on National Forests. 68th Annual Meeting, Society for Range Management. Corpus Christi, TX: Society for Range Management.
• Mcclaran, M. P., Hawkes, K., Brugger, J., Crimmins, M. A., Tolleson, D., Howery, L. D., Ruyle, G. B., & Sprinkle, J. E. (2016, October). Using an Interactive Scenario-Planning Tool for Ranchers and Forest Service to Prepare for Drought. 13th RISE Symposium (Research Insights in Semi-arid Environments). Oct. 8, 2016.. Tucson, AZ: College of Agriculture and Life Science.
• Mcclaran, M. P., Rawoot, D., & Fisher, L. (2016, Fall). Spatial distribution of conservation easements in relations to protected areas and grasslands in the Maderan Archipelago.. 13th Symposium on Research Insights in Semi-arid Environments (RISE).. Tucson, AZ: College of Agriculture and Life Sciences.
• Mcclaran, M. P., Ruyle, G. B., & Noelle, S. (2016, Fall). Short-term Rangeland Monitoring Archive: A New Resource for Researchers.. 13th Symposium on Research Insights in Semi-arid Environments (RISE).. Tucson, AZ: College of Agriculture and Life Sciences.
• Lohani, S., Heilman, P., Desteiguer, J. E., Guertin, D. P., Wissler, C. A., & Mcclaran, M. P. (2014, December). Linking ecosystem services with state-and-transition models to evaluate rangeland management decisions. AGU Fall Meeting.
• Dalke, A., & Mcclaran, M. P. (2013, February). Native and introduced perennial grass abundance responds differently to grazing,. 66th Annual Meeting, Society for Range Management. Oklahoma City, OK: Society for Range Management.
• Jernigan, M., Fehmi, J. S., Mcclaran, M. P., & Biedenbender, S. (2013, Aug). Use of uprooted invasive buffelgrass (Pennisetum ciliare) parent plants as thatch to reduce progeny seedling emergence. 98th Annual meeting of the Ecological Society of America. Minneapolis, MN: Ecological Society of America.
• Mcclaran, M. P., & Wei, H. (2013, fall). Frequency and duration of drought patches across the Santa Rita Experimental Range, 1940-2012.. 10th Annual Symposium on Research Insights in Semi-arid Environments (RISE). Tucson, AZ.
• Wei, H., & Mcclaran, M. P. (2013, summer). Spatial scale of drought in a meso-scale southwestern watershed.. Soil and Water Conservation Society Annual Meeting. Tucson, AZ: Soil and Water Conservation Society.

Others

• Sheehy, C., & McClaran, M. (2012, Fall). Photo Monitoring on the Santa Rita Experimental Range. Global Rangeland Web Site catalog of videos for Vegetation Monitoring. http://www.youtube.com/watch?v=GHjmM2iAD6s&list=PL7CD3CD7A9350A858&index=5; http://globalrangelands.org/content/multimedia