Community Assembly in a Changing World

How strongly does climate influence the composition of communities? If climate is the predominant force structuring communities, climate change should predictably result in the loss of cold-adapted species at the expense of warm-adapted species in local communities. Alternatively, if climate doesn’t strongly structure communities or microclimatic refugia buffer communities from regional climate trends, community composition in some locations may not change much with climate change. However, apparent stasis in community structure with warming can also arise from the failure of component species to shift their ranges with warming, due to (for example) recruitment limitation or demographic inertia. Unfortunately, these two have very different implications; the first suggests communities may be somewhat resilient to climate change, while the latter implies lagged community sensitivity, especially as climate change accelerates.

To explore the potential for community resilience vs. sensitivity to recent and future climate change, I am collaborating with Amy Angert (and various members of our groups) to resurvey plant community composition at >1000 plots located in Mt. Rainier National Park and North Cascades National Park (WA, USA). These plots were first surveyed in the 70's / 80's, and resurveys will allow us to determine the extent to which plant communities have already responded to recent warming, and how local microclimate influences community shifts. We are also conducting an extensive seed addition experiment on the east and west flanks of the Cascade Mountains (WA, USA) to assess how macro- and microclimatic effects on regeneration influences seedling recruitment.