Small-scale environmental variations drive vegetation structure and diversity in Amazon riverine forests

Abstract

Riverine forests in the Brazilian Amazon provide a series of ecosystem services and harbor one of the world's most diverse floras, but the main drivers of variation in small spatial scales in such tropical forests are not well understood. Our aim was to evaluate tree community structure and diversity patterns in the Teles Pires River to identify the main drivers of small-scale variations in the area. We sampled 4,180 individuals from 49 botanical families, 164 genera and 347 species by using six transects of five pairs of 50 m x 40 m permanent plots totalizing 60 permanent plots in a 12-hectare area. We utilized generalized linear mixed models to assess whether the effects of the environmental variables in the vegetation structural parameters. Altitude and groundwater depth were the main drivers influencing species diversity patterns. The trees had similar total biomass in areas within the same distance from the river margins. There was a lower species richness and tree density closer to the river margins. Otherwise, we found larger trees (higher individual biomass) closer to the river margins when compared to areas distant from the margins. Our results indicate a high species turnover from the river margins to the forest interior, which highlights the importance of assessing local effects on biological communities in tropical forests, especially in the Brazilian Amazon where several high-impact dams are planned. © 2021 Elsevier GmbH