Keywords: Forests, ecology, climate change, complexity, distribution shifts
Forest ecosystems across the U.S. have been recently threatened by climate change, invasive species, and other anthropogenic factors. While many studies have analyzed species-level changes in forest ecosystems, much less attention has been paid to forest communities. Identifying and quantifying shifts in forest tree communities can reveal how forest ecosystem functioning and services are impacted by climate change and other stressors. Utilizing an extensive dataset from the Forest Inventory and Analysis Program (FIA), we identified forest communities of the eastern U.S. using the Latent Dirichlet Allocation (LDA) topic model. In addition, we detected geographic shifts of these communities over the last three decades by evaluating movement of the community centroid and expansion or contraction of the community area. In total, LDA identified 15 communities in the eastern U.S. The mixed pine-oak-hickory community of the Southern Pine-Hardwood Region had the largest area, and the oak-hickory community of the Central Hardwoods Region had the largest overall abundance. In total, about half of the communities changed significantly, with a mixture of shifts in community centroid, and both expansions and contractions of community area. However, climate change factors (changes in temperature, precipitation, and drought severity) were poor predictors of community change. This may reflect resilience of forest communities to climate change, but it may also indicate a lag between climate change and forest community responses or the importance of other stressors on forest communities.