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.
The Sevilleta LTER Program addresses ecological concepts and theory through comprehensive and interdisciplinary research in desert grassland, shrubland, forest and riparian habitats in central New Mexico. Our focal sites are the Sevilleta National Wildlife Refuge (SNWR), the Middle Rio Grande (MRG), and the New Mexico Elevation Gradient flux tower network. Our studies are linked by an overarching goal to determine how abiotic drivers and constraints affect dynamics and stability in aridland populations, communities and ecosystems. SEV research investigates the individual and interactive effects of three integrated thematic areas: abiotic pulses and constraints, ecosystem processes, and biotic responses and feedbacks. The main abiotic pulses and constraints are (1) seasonal, annual, and decadal variations in climate, (2) geomorphology, soil texture, structure and depth, and surface and subsurface hydrology, and (3) season, periodicity, and intensity of fire and drought. These abiotic factors affect ecosystem processes including (1) biogeochemical pools and cycles, (2) soil water distribution, storage, use and loss, (3) patterns and controls on NPP, and (4) C storage and fluxes. Biotic responses and feedbacks include the dynamics of plant-environment, plant-plant and plant-animal interactions. These focal components and activities directly address the five LTER Network core research areas. Essentially, our LTER research links climate dynamics, disturbances, and soil processes with soil nutrient and water fluxes to understand seasonal and annual variability in NPP, and how that variability ultimately affects the dynamics, distribution, abundance and interactions of key populations of aridland producers and consumers. To accomplish our overarching goal, SEV LTER program has established several long-term manipulative experiments and observational studies that allow us to determine rate and direction of change in ecological communities as well as the mechanisms driving these changes. Our results suggest that our regional climate will become more arid in the future as a consequence of increasing mean annual temperature and a precipitation regime that will be more variable both within and between years. Increased aridity in combination with several important biological factors, such as bark beetles or grazing by domestic cattle, will lead to shrub encroachment into grasslands, widespread tree mortality in mountain forests, and the likelihood of larger and more devastating fires throughout the southwestern US. In combination, these factors will increasingly impact the ability of these ecosystems to provide and maintain ecosystem services, including carbon sequestration and water quality in the Rio Grande.
