Temporal vegetation changes in a seasonally dry tropical forest enclave in an ecotonal region between savanna and semiarid zones of Brazil

Abstract

Seasonally dry tropical forests (SDTFs) comprise a globally significant biome for biodiversity and conservation. Geographically, Brazilian SDTFs are primarily located within the country’s semiarid region (the Caatinga domain) in north-eastern Brazil. However, poorly studied and disjunct SDTF enclaves can occur within other regions, inside other Brazilian phytogeographical domains of vegetation such as savannas (i.e. the Cerrado domain) in central Brazil. These enclaves provide an opportunity to examine natural and non-anthropogenic edge effects on such vegetation. In 2007 and 2014, we studied a 120-ha SDTF enclave in the municipality of Januária in northern Minas Gerais, Brazil, to understand its (1) floristic composition and soil correlates, and (2) temporal variations in diversity, structure and dynamics. Three sets of 10 400-m2 plots were used to compare the vegetation at 0 m (edge), 100 m (middle) and 200 m (inner) into the forest. The edge plots were compositionally dissimilar from the interior plots because of soil fertility and soil textural gradients. Paradoxically also, the inner plots exhibited less stable vegetation-dynamic patterns than did both the middle and the edge plots, possibly owing to natural temporal fluctuations in vegetation dynamics. Overall, the SDTF enclave exhibited high diversity and structural complexity, likely because of its geographical setting within a matrix of savanna. These results highlight a conservation priority for further studies on such SDTF enclaves throughout their range.