Mechanisms of plant and ecosystem responses to climate warming and increased atmospheric nitrogen deposition in temperate regions

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My research objective is to determine plant and ecosystem responses to climate change and increased atmospheric nitrogen pollution from industrial and agricultural sources in northern temperate regions. While both of these factors are expected to have substantial effects on plants and ecosystems over the next century, their potential interactions remain unclear. Based on preliminary studies conducted using my previous NSERC Discovery Grant, I hypothesize that while a longer growing season might be expected to increase plant growth, reduced snow cover caused by warming and more extreme climate events will likely increase the intensity of soil freezing, which can damage plants and soil organisms, leading to increased soil nitrogen losses and reduced plant growth. I will explore the combined effects of warming and nitrogen addition in the context of a long-term experiment I have established in a grass-dominated field in London, ON. In addition to monitoring the plant responses to warming (administered using overhead heaters) and nitrogen addition, I am examining the pathways by which nitrogen is lost from the soil in response to the treatments. I will also study plant freezing responses under controlled laboratory conditions and in the field to determine how soil freezing influences root nitrogen uptake. In addition to my research on plants and nitrogen, I will explore entire ecosystem responses in the context of my field experiment. I will examine how the activities of herbivores and decomposers alter our perception of how the plants respond to the experimental treatments. I will also measure the extent to which warming and increased nitrogen alter the release and containment of carbon dioxide by the ecosystem. These data are particularly important for predicting how biological feedbacks to climate change will influence future greenhouse gas concentrations. Overall, my research will have important implications for the management of natural plant communities and agricultural systems and for predicting how ecosystem services may change in response to global change over the next century.