Global environmental change and the dynamics of grassland ecosystems

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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.