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。一般来说，植物群落是受限制的，因此结构，池的大小和流量的限制资源。全球环境变化的重要性在于它从根本上重新配置这些池和流动的方式，但理解这是如何发生的，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的同时影响（例如，全球变暖，氮污染，入侵，栖息地丧失），（2）许多转变可能早在生态学家开始研究它们之前就开始了，从而模糊了它们的因果起源，（3）环境变化的特定组合可能对北美不同地区的植物群落产生不同的影响。我的研究计划旨在解开这些因素中的每一个是如何与当代变化的结构和功能的草原植物群落（例如，物种损失、土壤退化）。使用现场和温室实验，我的工作集中在三个退化草原，或邻近，加拿大南部：沿海橡树稀树草原西南部的不列颠哥伦比亚省，蒙大拿州西北部的半干旱草原，和高草草原西南部的安大略。所有这些都受到气候变化、植物入侵、栖息地丧失、火灾或放牧抑制的影响，这使我能够测试具有相似干扰历史但不同地理环境的系统中各种环境变化模型的普遍性。我的研究成果将扩大我们对全球环境变化如何影响草原生态系统的理解，以及如何通过管理干预减少这些影响。由于草原对生物多样性、农业、大气碳的地下储存和一般生态研究的重要性，我的工作具有广泛的理论和实践价值。

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 field and greenhouse experiments, my work focuses on three degraded grasslands in, or adjacent to, southern Canada: coastal oak savanna of southwestern British Columbia, semi-arid prairie of northwestern Montana, and tallgrass prairie of southwestern Ontario. 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 ecological research generally, my work has wide-reaching theoretical and practical benefits.