Sevilleta LTER: Abiotic pulses and constraints: effects on dynamics and stability in an aridland ecosystem

 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 grass to shrub state transition in response to multiple anthropogenic drivers. This life-form shift has important consequences for evapotranspiration, net primary production, carbon fluxes and biodiversity.

 Our LTER research 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, our research across multiple time and space scales is yielding a comprehensive understanding of how key abiotic drivers affect pattern and process in aridland ecosystems. The goals of LTER IV are to: 1) continue our long-term datasets on ecosystem processes and dynamics developed over the past 18 years, 2) create a comprehensive understanding of how various global change drivers affect pattern and process in aridland ecosystems, 3) develop, test, and contribute to general ecological theory, 4) enhance our information management system to meet LTER goals, and 5) create a comprehensive program that integrates research with undergraduate and graduate education and training.

To accomplish these goals we continue to expand our existing long-term datasets on climate, evapotranspiration and nutrient fluxes, net primary production and carbon fluxes, and plant and animal community dynamics. We have several rainfall addition experiments to complement our existing drought experiment. We measure belowground production and have a variety of studies on the drivers of plant community dynamics. In addition, we are using stable isotope tracers to follow resource use by consumers under fluctuating environmental conditions. Finally, we are conducting pioneering research on the ecological restoration of Gunnison’s prairie dog in desert grassland. Overall, our research is yielding a broader understanding of pattern and process in aridland ecosystems, and an improved ability to predict how global environmental change will affect population, community and ecosystem processes in Chihuahuan Desert ecosystems.