Dr. Janet Franklin, UC Riverside
Ecosystems navigate complex terrain in a changing climate

Microclimates describe the conditions experienced by individual plants and the heterogeneous microclimates found in mountainous terrain may allow tree species to persist in a changing climate, buffering species’ exposure to regional climate change. Seedling establishment is a sensitive stage of tree regeneration that may govern species' local persistence and migration under environmental change. We found, using the results of a common garden experiment, that interannual variability in climate can provide windows of opportunity for tree seedling establishment that are overlooked when long term climate averages are used to predict climate-change effects on forest distributions. We also investigated the role of topo-climatic suitable sites of establishment in conjunction with disturbance and succession in mediating forest range shifts in California using a spatially explicit simulation model. Disturbance (fire) regimes were important in mediating species range changes during climate change, expediting range contractions for some species and facilitating range shift and expansion others. Topo-climatically suitable sites generally had a smaller effect on range changes than disturbance, enhancing persistence of some species, but hampering migration under some disturbance regimes for species with low dispersal capabilities. Effects of rapid, anthropogenic climate change on forest range changes will likely be modulated by complex tradeoffs between landscape heterogeneity, disturbance regimes and species functional traits. The study is part of a project integrating climate model downscaling, microclimate measurements, experimental studies of seedling recruitment, and spatially explicit plant population models to link micro-scale ecological processes to macro-scale forest dynamics under climate change (funded by the National Science Foundation’s MacroSystems Biology Program).