Long-term shifts in the functional composition and diversity of a tropical dry forest: a 30-yr study

Over the past three decades, there has been a concerted effort to study the long-term dynamics of tropical forests throughout the world. Data regarding temporal trends in species diversity, species composition, and species-specific demographic rates have now been amassed. Such data can be utilized to test predictions regarding the roles the environment and demographic stochasticity play in driving forest dynamics. These analyses could be further refined by quantifying the temporal trends in the functional composition and diversity in tropical forests. For example, we have only a handful of studies that quantify directional shifts in the functional composition in tropical forests in response to global change drivers. The present study uses data from three censuses spanning 30 yr in a Neotropical dry forest dynamics plot to provide novel insights into how the functional diversity and composition of a tropical forest has changed through time. Specifically, here we aim to (1) quantify population dynamics and compare it to that expected from environmental or demographic variance; (2) quantify long-term trends in species richness and functional diversity; (3) test whether there have been directional changes in the functional composition of the forest though time and the population changes that are responsible for these changes; and (4) place these long-term results into the context of the successional and climatic history of the forest.