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

Sevilleta LTER（SEV）建议继续并扩大对Sevilleta国家野生动物保护区及其周围干旱土地生态的长期研究。虽然水是干旱地区生态系统的主要限制资源这一点是不言自明的，但大多数干旱地区的土壤也长期缺乏养分和有机质。养分有效性是降水事件的频率和大小以及事件之间的时间的函数。因此，净初级生产力和有机质分解往往是解耦的空间和时间，土壤养分供应率可能会限制净初级生产力期间，土壤水分是足够的植物生长。此外，世界各地的干旱和半干旱生态系统正在经历一个状态过渡，从草为主的社区到灌木为主的社区，以应对多种人为驱动因素。这种生命形式的转变对蒸散量、净初级生产力、碳通量和生物多样性产生了重要影响。SEV研究计划整合了对多个全球变化驱动因素和脉冲降水动力学的研究，以确定它们如何影响这种草地到灌木过渡发生的速度。跨多个时间和空间尺度的正在进行的和新的研究将全面了解关键的非生物驱动因素如何影响这些系统中的模式和过程。目标是：1）继续收集过去18年来开发的关于生态系统过程和动态的各种数据集，2）开发新的观测和实验项目和综合，3）全面了解各种全球变化驱动因素如何影响干旱地区的格局和过程，4）发展、测试和促进一般生态理论，5）加强信息管理系统，以更好地实现长期环境影响报告目标，以及6）创建一个将研究与本科和研究生教育和培训相结合的综合计划。SEV建议增加一个降雨增加处理，以补充现有的干旱实验，并增加一个新的季风脉冲降雨实验。它将增加对地下生产的研究，并将增加对植物和动物群落的新研究，包括建立新的草原土拨鼠群落。最后，将开始一项关于三个全球变化驱动因素对社区和生态系统进程的互动影响的实验，这项研究将使人们更广泛地了解干旱土地生态系统的模式和进程，并提高预测全球变化将如何影响这些系统的能力。鉴于干旱和半干旱土地占陆地环境的30%，SEV研究具有全球意义和应用。总的来说，研究问题是由基本生态理论驱动的，研究计划将产生信息，并创造广泛的生态利益的知识。更广泛的影响包括K-12教育和推广，以及整合本科生和研究生培训的研究。最后，SEV研究与野生动物保护区的管理、整个新墨西哥州中部的水资源保护以及对全球干旱土地生态系统的了解有关。

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.