LTER V: Long Term Pulse Dynamics in an Aridland Ecosystem

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Arid-land ecosystems cover more than 40% of continental land area of the Earth. They support local economies comprised of ranchers, farmers, and pastoralists around the world. Transitions from grass- to shrub-dominated communities are increasing in frequency, threatening human well-being and these economies in both developed and developing countries. This long-term project explores the diverse mechanisms responsible for these changes in an effort to predict the future of arid-land habitats. Clear understanding of underlying mechanisms is necessary to maintain arable land and ecosystem services necessary for human well being. The project engages hundreds of middle and high school students and teachers who sample along the Middle Rio Grande, a highly visible and highly disturbed ecosystem. The resulting data are used by local conservancy groups, the US Army Corps of Engineers, the US Bureau of Reclamation, and the US Fish and Wildlife Service, to name a few among many agencies, in management of an economically and culturally important region. Participants in the Bosque Ecosystem Monitoring Program blend Hispanic, Native American, and Anglo cultures and integrate participants from inner-city, suburban, and rural areas. By connecting K-12 and university students in scientific research, the project enhances education in STEM fields. Undergraduate training is also extensive, involving national efforts to recruit under-served groups into science and participation from the Southwest Indian Polytechnic Institute. Research at the Sevilleta Long Term Ecological Research site seeks to understand how abiotic drivers and constraints affect the pulse dynamics and stability of arid-land populations, communities, and ecosystems. This award will extend previous research on short-term, local-scale processes to understand pulse-driven regional-scale transitions and transfer of materials between landscape units. An experiment at the grassland-shrubland transition will be initiated to understand the roles of shallow versus deep soil moisture in plant and microbial exchanges and associated ecosystem processes. A rain manipulation will impose large monsoons to assess the impact of rainfall pulses, and manipulations of fragile bio-crusts will document exchanges and biotic interactions underlying a novel loop by which fungi integrate ecosystem functions by transforming, translocating, and storing C and nutrients. New research in pinon-juniper woodlands will examine plant function across this transition and assess microbial community responses to water manipulations. This research will compare the role that fungi play in woodlands with the roles that microbes play in grasslands. High resolution measurements of daily and seasonal changes in water quality and quantity will be used to document how disturbances such as fire interact with pulses of rain to transfer nutrients and organic matter into tributaries that feed the Rio Grande River. Results from these diverse activities will be integrated, using simulation models, to document the effects that precipitation pulses have on plant recruitment, growth, and mortality of different species at the plant to patch scale, and how these drive long-term patterns in dominance and composition across landscapes.