Sevilleta LTER IV: Abiotic Pulses and Constraints: Effects on Dynamics and Stability in an Aridland Ecosystem

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Sevilleta LTER (SEV) proposes to continue and expand long-term research in arid land ecology in and around the Sevilleta National Wildlife Refuge. Although it is axiomatic that water is the key limiting resource in aridland ecosystems, most arid land soils are also chronically low in nutrients and organic matter. Nutrient availability is a function of the frequency and size of precipitation events as well as the time between events. As a consequence, net primary production and organic matter decomposition are often decoupled in space and time, and soil nutrient supply rate may limit net primary production during periods when soil moisture is sufficient for plant growth. In addition, arid and semiarid ecosystems worldwide are undergoing a state transition from grass- to shrub-dominated communities in response to multiple anthropogenic drivers. This life form shift has important consequences for evapotranspiration, net primary production, carbon fluxes and biodiversity. The SEV research program integrates studies on multiple global change drivers and pulse precipitation dynamics to determine how they affect the rate at which this grass-to-shrubland transition occurs. Together, on-going and new research across multiple time and space scales will yield a comprehensive understanding of how key abiotic drivers affect pattern and process in these systems.The goals are to: 1) continue collection of diverse datasets on ecosystem processes and dynamics developed over the past 18 years, 2) develop new observational and experimental projects and syntheses, 3) create a comprehensive understanding of how various global change drivers affect pattern and process in arid lands, 4) develop, test and contribute to general ecological theory, 5) enhance the information management system to better meet LTER goals, and 6) create a comprehensive program that integrates research with undergraduate and graduate education and training. The SEV proposes to add a rainfall addition treatment to complement an existing drought experiment, and to also add a new monsoon pulse rainfall experiment. It will increase studies of belowground production and will add new studies on plant and animal communities, including the establishment of new prairie dog colonies. Finally, it will start an experiment on the interactive effects of three global change drivers on community and ecosystem processes.This research will generate a broader understanding of pattern and process in arid land ecosystems, and an improved ability to predict how global change will affect these systems. Given that arid and semi-arid lands occupy 30% of terrestrial environments, SEV research has global relevance and application. Overall, the research questions are driven by basic ecological theory, and the research program will yield information and create knowledge of broad ecological interest. The broader impacts include K-12 education and outreach, and research that integrates undergraduate and graduate training. Finally, SEV research is relevant to management of the Wildlife Reserve, water conservation throughout central New Mexico, and understanding arid land ecosystems worldwide.