Global environmental change and the dynamics of grassland ecosystems

全球环境变化正在改变所有植物群落的多样性和功能，但这些变化发生的途径仍然不清楚。一般说来，植物群落受到限制资源的池大小和流速的限制，因此具有结构性。全球环境变化的意义在于它从根本上重新配置这些池和流的方式，但理解这种变化是如何发生的，以及它对群落结构的影响，受到以下几个因素的挑战：(1)在一系列空间尺度上作用的多种变化(例如，全球变暖、氮污染、入侵、栖息地丧失)的同时影响，(2)许多变化在生态学家开始研究它们之前很久就开始的可能性，从而掩盖了它们的原因来源，以及(3)环境变化的特定组合对北美不同地区植物群落产生不同影响的可能性。我的研究计划试图解开这些因素中的每一个如何与草原植物群落结构和功能的当代变化(例如，物种丧失、土壤退化)相关联。我的工作重点是加拿大南部退化的草原，主要使用基于实地的方法。所有这些都受到气候变化、植物入侵、栖息地丧失和火灾或放牧抑制的影响，这让我能够在具有相似干扰历史但不同生物地理背景的系统中测试各种环境变化模型的普遍性。我的研究结果将扩大我们对全球环境变化如何影响草原生态系统，以及如何通过管理干预来减少这些影响的理解。由于草原对生物多样性、农业、大气碳地下储存以及基本生态学理论的检验的重要性，我的工作具有广泛的好处。

Global environmental change is transforming the diversity and functioning of all plant communities but the pathways by which these transformations occur remain obscure. Generally, plant communities are constrained, and therefore structured, by the pool sizes and flow rates of limiting resources. The significance of global environmental change is the way it fundamentally reconfigures these pools and flows, but understanding how this occurs, and its consequences for community structure, is challenged by several factors: (1) the simultaneous influence of multiple changes acting at a range of spatial scales (e.g., global warming, nitrogen pollution, invasion, habitat loss), (2) the likelihood that many transformations started long before ecologists began studying them thereby obscuring their causal origins, and (3) the likelihood that specific combinations of environmental change affect plant communities differently in different regions of North America. My research program seeks to untangle how each of these factors is associated with contemporary changes to the structure and function of grassland plant communities (e.g., species loss, soil degradation). Using mostly field-based approaches, my work focuses on degraded grasslands of southern Canada. All are affected by climate change, plant invasion, habitat loss, and fire or grazer suppression, allowing me to test for the generality of various models of environmental change in systems with similar disturbance histories but different biogeographical contexts. The outcome of my research will broaden our understanding of how global environmental change is affecting grassland ecosystems, and how these impacts may be reduced by manangement interventions. Because of the importance of grasslands for biodiversity, agriculture, the belowground storage of atmospheric carbon, and the testing of fundamental ecological theory my work has wide-reaching benefits.