Community Change in an Arid Ecosystem

亚利桑那州东南部的圣西蒙山谷在过去30年的大部分时间里保持着高度的植物多样性。 然而，在20世纪90年代中期，这个植物群落经历了一个戏剧性的变化与持续入侵的冬季一年生植物，Erodium cicutarium。 随着入侵植物的增加，冬季一年生植物多样性急剧下降，物种组成发生了变化，食种子的啮齿动物群落发生了变化。 本研究运用生理学、生态学、群落学和理论等方法，对导致E. cicutarium，及其对当地生态系统的主要影响。 这些环境因素包括最近的气候变化（冬季降雨量减少和干旱更加频繁）、氮沉降形式的污染（来自农田和附近的铜冶炼厂）以及啮齿动物群落的变化（从袋鼠鼠占优势变为口袋鼠占优势）。 从现场操作和生长室研究的结果将形成数学模型的基础，以预测在未来的气候和养分富集制度下的一年生植物群落和生态系统的功能的变化。 这些模型应阐明人类在这一生态系统中的作用。 这项工作的结果将为干旱生态系统中植物入侵的缓解和管理策略提供信息，并有助于恢复本地植物群落。 该项目还为本科生、研究生和一名博士后研究员提供重要的研究培训。 它将支持在妇女和少数民族人数不足的科学学科中对她们进行培训。

The San Simon Valley of southeastern Arizona maintained high plant diversity over much of the past 30 years. However, during the mid-1990's, this plant community underwent a dramatic change associated with the sustained irruption of the invasive winter annual plant, Erodium cicutarium. Coincident with the increase of this invasive plant, the winter annual plant diversity dramatically declined, species composition shifted, and the seed-eating rodent community changed. This research utilizes physiological, ecosystem, community and theoretical approaches to disentangling the various environmental factors hypothesized to have led to the dominance of E. cicutarium, and its major impacts on the local ecosystem. These environmental factors include recent changes in climate (decreased winter rainfall and more frequent drought), pollution in the form of nitrogen deposition (from agricultural fields and nearby copper smelters) and changes in the rodent community (from dominance by a kangaroo rat to dominance by a pocket mouse). Results from field manipulations and growth chamber studies will form the basis of mathematical models to predict changes in the annual plant community and in the functioning of the ecosystem under future climate and nutrient enrichment regimes. These models should elucidate the roles of human drivers of change in this ecosystem. Results from this work will inform mitigation and management strategies for plant invasions in arid ecosystems, and should aid efforts to restore native plant communities. This project also has an important research training component for undergraduates and graduate students and a postdoctoral fellow. It will support the training of women and minorities in a scientific discipline where they have been underrepresented.