We are a research group in the Institute of Ecology and Evolution at the University of Oregon studying what controls the distributions of species and composition of communities in forest and grassland ecosystems. This work has become more challenging and more urgent in this era of rapid global changes. Species distributions and phenologies (timing) are reshuffling due to species-specific responses to changing climate and human-mediated movements of species. We use these changes as natural experiments to ask basic questions about what processes shape ecological communities while also building capacity for forecasting change in the coming decades. We use field experiments, greenhouse experiments, theory, and demographic and statistical modeling that can test hypotheses and quantify processes at different spatial and temporal scales.