Woody plant community structure in “Dense Cerrado” fragments in the Upper Basin of the Araguaia River (Central Brazil): relationship with habitat loss and geographical distance

Abstract

Habitat loss and fragmentation are severe threats to biodiversity but have been little explored in studies of the woody vegetation of the Cerrado. The present study addressed the community structure of woody plants in 17 “Dense Cerrado” fragments in the Upper Basin of the Araguaia River (GO and MT), standardizing variables such as fragment size (>50 ha), shape, disturbance and matrix. The phytosociological structure was assessed with an inclusion criterion of D30 ≥ 5 cm in three plots, 50 × 20 m each, per fragment. A total of 131 species were recorded. Pielou’s equitability index was equal to 0.82, and Shannon’s diversity index (H′) was equal to 4.03 nats/ind.−1. Basal area and density were equal to 18.13 m2 ha−1 and 1715.49 ind. ha−1, respectively. The estimated richness (Jackknife 1) was superior to the observed richness. The assessment whether density, observed diversity and Shannon’s diversity index for each fragment explained either fragment size or habitat lost in 28 years revealed that these parameters did not explain either the woody community structure or the species diversity. The assumption that the fragments with the greatest area loss throughout this time period would have less diverse communities was not corroborated. The results of the Mantel test did not demonstrate any relationship between geographical distance and floristic similarity in “Dense Cerrado” fragments; therefore, it was not possible to corroborate the hypothesis that fragments located closer to each other are more floristically similar. As suggested by some authors, the floristic similarity in Cerrado areas can be better explained by other factors than geographical distance among sampled sites.