Long-term Shifts in Community Dynamics in a Central American Dry Tropical Forest

Tropical regions have been experiencing extreme seasonal heat, rapidly increasing temperatures and variability in precipitation due to climate change. In tropical dry forests, declines in tropical tree performance in response to variation in climate have caused directional shifts in forest community composition, ultimately altering ecosystem structure and function. Here, we analyze 41 years of census data (1976-2017) to describe changes in overall tree abundance and community composition within a subset (1-ha) of the San Emilio Forest Dynamics Plot (SEFDP) in Guanacaste, Costa Rica. From 1976-2017, changes in composition favored increased proportions of evergreen, compound leaf and canopy trees along with later successional species, while simultaneously reducing proportions of deciduous, simple leaf and understory trees and earlier successional species. Significant differences in functional leaf and wood traits were observed among species related to their proportional change in basal area from 1976-2017. Species that became more dominant in the community over time exhibited a tradeoff between conservative strategies and acquisitive traits. These results support previous work showing that the San Emilio Forest Dynamics Plot is dynamic and undergoing significant directional changes in species composition while increasing in basal area (BA) over time. Our results highlight the need for long-term studies that combine climate, compositional and functional trait data to determine the mechanisms driving change in tropical forest ecosystems.