LTREB Renewal: Multiscale effects of climate variability and change on hydrologic regimes, ecosystem function, and community structure in a desert stream and its catchment

河流和湿地生态系统提供由气候决定的重要生态系统服务，例如供人类使用的水以及为鱼类和野生动物提供栖息地支持。在美国西南部的沙漠中，极端干旱的年份往往伴随着非常潮湿的年份，因此不可能根据平均条件来定义河流生态系统的服务。事实上，高变异性是该地区河流水文状况的恰当描述。在这个项目中，研究人员正在使用新的统计技术来描述水文制度，再加上对河流结构和过程的长期测量，以了解气候和河流排放制度在许多时间尺度上的变化将如何影响生态系统。研究将集中于解释为什么湿地植物的丰度和分布以及氮限制程度在不同年份之间变化巨大的因素。此外，春洪后变化模式的年际变化——初级生产、营养保持和群落组成（无脊椎动物和植物）——将与水文的年内和年内变化有关，以确定各种制度对这些演替模式的影响。最后，一个跨学科的合作团队将重新评估河流生态系统模型，并使用来自这条和其他沙漠河流的长期数据测试新模型。这项研究将促进对来自沙漠河流的长期数据的综合，并促进对多种生态系统状态稳定性的一般理论的理解。研究生主导的研讨会将给予学生使用长期数据库的经验，并促进协作互动。一个合作实验室的活动将扩大创新性水文时间序列分析与生态数据的耦合。这一众所周知的河流生态系统的数据库将扩展到40多年，并提供给科学和管理界，在气候变化和人口增长的压力因素正在汇聚的高度变化的环境中，有可能为管理提供信息。

River and wetland ecosystems provide important ecosystem services that are determined by climate, such as water for human uses and habitat support for fish and wildlife. In southwestern deserts of the United States, years of extreme drought often follow years of very wet conditions, thus it is impossible to define river ecosystem services in terms of average conditions. In fact, high variability is an apt descriptor of the hydrologic regimes for streams in this region. In this project, researchers are using new statistical techniques that describe hydrological regimes, coupled with long-term measurements of stream structure and processes, to understand how shifts in climate and river discharge regimes on many time scales will influence the ecosystem. The research will focus on factors that explain why the abundance and distribution of wetland plants and the degree of nitrogen limitation vary dramatically among years. Also, the variation among years in patterns of change after spring floods - in primary production, nutrient retention, and community composition (of invertebrates and plants)- will be related to within- and among-year variation in hydrology, to determine the impact of regimes on these successional patterns. Finally, an interdisciplinary team of collaborators will reevaluate stream ecosystem models and test new models using long-term data from this and other desert streams. This research will advance synthesis of long-term data from desert streams and advance understanding in ways that can contribute to the general theory of stability of multiple ecosystem states. A graduate student-led workshop will give students experience in using long-term databases and foster collaborative interactions. Activities of a collaboratory will expand the coupling of innovative hydrologic time-series analyses with ecological data. The database for this well-known stream ecosystem will be extended to more than 40 years and made available to the scientific and management community, potentially informing management in a highly variable environment where stressors of climate change and population growth are converging.