The Rapid Recovery of a Caatinga Dry Forest is Mediated by Disturbance-Adapted Species

Abstract

Tropical dry forest regeneration in human-modified landscapes may be more complex than previously proposed, since the remaining forest is permanently exposed to myriad of human disturbances. We examined the regeneration of a Caatinga dry forest in the context of extraction of forest products and livestock production to reveal patterns and potential mechanisms driving forest regeneration in a human-modified landscape. Seed, seedling, and adult assemblages from woody species were sampled across a forest chronosequence and old-growth forest (OGF) stands. Community-level metrics were related to the age of regenerating forest stands, precipitation, and human-chronic disturbances via linear and non-linear statistical models and multivariate analyses. Overall, regenerating and OGF stands exhibited similar stem abundance and species richness across all ontogenetic stages. Little directional changes occurred along forest regeneration, with a negligible role played by forest stand age, precipitation, and chronic human disturbance. Moreover, species exclusively recorded as adults or seeds were mostly dispersed by animals, indicating that several species fail in either dispersing or recruiting due to human disturbances (e.g., defaunation) and harsh environmental conditions. In short, the apparent fast recovery of Caatinga is due to a low diversity and the predominance of species abiotically dispersed and able to resprout, suggesting a human-driven degradation trajectory rather than a natural condition.