Community Change in an Arid Ecosystem

亚利桑那州东南部的圣西蒙谷在过去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，该植物群落经历了剧烈的变化，与入侵的冬季一年生植物黄花Erodium cicutarium的持续入侵有关。随着该入侵植物的增加，冬季一年生植物多样性急剧下降，物种组成发生变化，食籽啮齿动物群落发生变化。本研究运用生理学、生态系统、群落和理论等方法，揭示了导致圆圆叶蝉优势的各种环境因素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（冬季降雨减少和干旱更频繁）、氮沉积形式的污染（来自农田和附近的铜冶炼厂）和啮齿动物群落的变化（从袋鼠鼠的优势地位变为口袋鼠的优势地位）。田间操作和生长室研究的结果将构成数学模型的基础，以预测未来气候和养分富集制度下一年生植物群落和生态系统功能的变化。这些模型应该阐明人类在这个生态系统中驱动变化的作用。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战略提供信息，并应有助于恢复本地植物群落的努力。该项目还包括本科生、研究生和博士后的重要研究培训部分。它将支持培训妇女和少数民族在其代表性不足的一门科学学科。

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.