Using restoration to test community assembly in a heavily invaded ecosystem

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Ecological restoration, the process of assisting the recovery of an ecosystem, is an essential tool for mitigating the effects of human-induced degradation in natural systems. For example, restoration in drylands has been used to fight desertification, and stream restoration can enhance habitat for fish such as salmon. Despite its importance, however, success in restoration projects can be difficult to achieve, and outcomes are often unpredictable. In light of these challenges, my research program seeks to link ecological theory and restoration practice to enhance the predictability and success of restoration. Over the next five years, I will use theories of community assembly and trait-based ecology to uncover mechanisms of ecological responses to disturbance, invasion, and restoration. Community assembly frameworks focus on how the environment acts to filter out species that are not well adapted to local conditions. Particularly strong filters will select for a subset of plant traits, such as dry conditions filtering out species that use water inefficiently. This can cause convergence within a community, with all species having a similar set of traits in response to the strongest filter. I will assess the role of disturbance as a filter in herbaceous communities through a combination of large- and small-scale field experiments and observational studies. Specifically, my research focuses on Garry oak meadows in British Columbia. Based on a gradient of low intensity deer pressure to high intensity, I will track community trait convergence as grazing intensifies. Disturbance is also linked to increased rates of invasion by non-native species, though this is generally understood in terms of arrival and colonization rather than traits intrinsic to exotic species. However, exotic species may represent a strongly biased set of reproductive and growth traits based on their relationship to humans, may be better represented in seed inputs, and may escape disturbances like grazing. Thus, exotic species' response to grazing may be distinct from natives, and may drive community assembly pre-, during, and post-disturbance in unpredictable ways if origin is ignored. As a result, my work will simultaneously consider disturbance and invasion in community assembly, both as drivers of composition in degraded communities and as predictors of recovery under restoration actions. I will assess grazing impacts on traits in native and exotic species separately and together, and will pull apart why exotic species may respond differently by tracking deer diet preferences, seed inputs in meadows, and bias in exotic species traits. Finally, I will test how managing grazing, removing exotics, or implementing both strategies influence restoration outcomes in native communities. My work will inform management in one of the highest priority conservation areas of Canada, and will enhance ecological understanding of how disturbance and invasion alter community assembly patterns.