Impoverished woody seedling assemblages and the regeneration of Caatinga dry forest in a human‐modified landscape

Abstract

AbstractSeedling recruitment, community assembly, and forest regeneration, while receiving substantial attention in tropical rain forests, have received little attention in tropical dry forests. Here, we examine the structure, composition, and diversity of woody seedling assemblages across 19 forest stands in a human‐modified landscape of Caatinga dry forest, assessing the role played by rainfall, aboveground biomass, and chronic anthropogenic disturbances (i.e., livestock grazing pressure and wood extraction) as assembly forces. We quantified a large set of community‐level attributes including functional traits related to water availability, physical protection, and survival success. We recorded a total of 544 seedlings from 59 species, giving a mean density of 28.6 ± 15.8 (mean ± SD) seedlings and 7.42 ± 4.35 species per 1000 m2. The 10 most abundant species accounted for almost 80% of all individuals, whereas nearly half of the species were considered rare (i.e., less than two individuals across the 19 forest stands). Seedling assemblages differed structurally and taxonomically from adult assemblages, exhibiting lower abundance, species richness, and divergent dominant species. Moreover, the dominant species of seedlings exhibited low adult‐to‐offspring ratios. Seedling species and assemblages were functionally diverse, with community‐level attributes mostly affected by rainfall. Our results suggest that the Caatinga dry forest in sandy soils support seedling assemblages, to some extent, structured along environmental gradients, with rainfall and wood extraction acting as key community assembly forces. Although seedling assemblages are functionally diverse, they are relatively low density and taxonomically impoverished at local and landscape scales, potentially impacting successional trajectory and long‐term forest dynamics.Abstract in Portuguese is available with online material.