Using plant traits to predict the sensitivity of colonizations and extirpations to landscape context.

Theory suggests that species with different traits will respond differently to landscape fragmentation. Studies have shown that the presence of species in fragments of varying size, shape and connectivity is dependent on plant traits related to dispersal ability, persistence and disturbance tolerance. However, the role of traits in determining long-term plant community changes in response to changing landscape context is not well understood. We used data from resurveys of 184 plots to test the ability of nine plant traits to predict colonizations and extirpations between 1968 and 2009 based on the surrounding landscape context. We related apparent colonizations and extirpations to road density, naturally vegetated area and patch shape and then tested for significant relationships between a tendency for positive or negative associations and plant traits. Exotic, herbaceous, annual, shade-intolerant species and species with higher specific leaf area were more likely than others to colonize plots with higher road density, lower amount of naturally vegetated area and higher edge-to-area ratio. However, extirpations were rarely predictable based on traits. The role of landscape context in structuring plant community change over the past four decades in the 184 plots resurveyed was largely mediated by colonization events, suggesting that trait-based extirpations occur with a longer post-fragmentation time lag or, alternatively, that extirpation is more stochastic with respect to plant traits than is colonization.