Precipitation Controls of Carbon and Nitrogen Cycles in Arid-Semiarid Ecosystems

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。尽管降水被认为是干旱和半干旱地区植物生产的主要控制因素，但年降水量仅解释了20-40%的草木和灌木生产年际变化。这一失败表明，研究人员没有考虑到控制干旱生态系统追踪降水波动能力的关键机制。然而，波动加剧是干旱地区气候预测的一个显著特征。本项目提出了四个假设来解释生态系统对降水变化响应的滞后现象，并通过改变总降水量和降水变率的模式对这些假设进行了验证。这些操作与模式分析一起，将有助于确定生态系统对降水响应滞后的原因和程度。该项目的结果将有助于了解气候变化对碳固存、饲料生产和灌木侵蚀过程的影响，这对美国西南部的利益相关者非常重要，从牧场主到担心水供应和生态系统服务的城市当局。一个示范项目将与一个非营利组织合作建立，该组织每年向新墨西哥州南部和德克萨斯州西部的12000多名儿童和4500多名成年人提供获奖的科学教育。此外，该项目将开发网站和外联材料，将研究结果传播到大学以外。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Although precipitation is assumed to be the major control of the production of plants in arid and semiarid regions, annual precipitation explains only 20-40% of grass and shrub production variability among years. This failure suggests that researchers are not accounting for key mechanisms that control the ability of arid ecosystems to track fluctuations in precipitation. Yet increased fluctuations are a prominent feature of climate predictions in arid regions. This project puts forward four hypotheses to explain observed lags in ecosystem response to changing precipitation, and tests them by altering patterns of total precipitation and precipitation variability, with and without nitrogen manipulation. These manipulations, together with the model analysis, will help determine the cause and magnitude of lags in the ecosystem response to precipitation. Results from this project will contribute to understanding the effect of climate change on carbon sequestration, forage production and the process of shrub encroachment, which are very important for stakeholders of the southwestern U.S., ranging from cattle ranchers to city authorities worrying about water supplies and ecosystem services. A demonstration project will be established in partnership with a nonprofit organization that provides award-winning science education to more than 12,000 children and 4,500 adults annually in southern New Mexico and western Texas. In addition, the project will develop web sites and outreach materials to transmit findings beyond the university.