Diversidade Florística e Estrutural em Uma Escala Regional da Amazônia Central

Abstract

The Amazon harbors the greatest plant diversity on Earth and represents one of the most complex tropical ecosystems in the world. With thousands of tree species spread across vast geographic expanses, understanding patterns of distribution, abundance, and the drivers of this diversity remains one of the key challenges in tropical ecology. This complexity is further compounded by subtle environmental gradients, logistical limitations, and sampling gaps, making it essential to adopt integrated approaches to better understand Amazonian biodiversity. In this context, this study investigated (Chapter I) the structure and composition of tree communities at a regional scale in Central Amazonia, revealing spatial patterns marked by the dominance of a few widely distributed morphospecies, such as matamatá, and by the presence of many rare species with low abundance. Tree density per hectare was found to be higher in the western and northwestern regions of Central Amazonia, although this density was not necessarily associated with higher alpha diversity. The analysis revealed a negative relationship between the density of common and rare species and identified longitude as an important predictor of alpha diversity. Beta diversity partitioning showed that species turnover along the spatial gradient is strongly related to geographic distance and forest structure, highlighting the importance of ecological and spatial processes in shaping community composition. In a complementary approach (Chapter II), the study also focused on an important functional group — arborescent palms (DBH ≥10 cm) — analyzing data from 1,545 forest inventory plots aggregated into 385 sampling points across different Amazonian ecoregions. The results showed that palm density, relative abundance, and basal area vary significantly across ecoregions and in response to environmental gradients. Among the variables analyzed, soil properties — particularly soil texture and silt content — were the best predictors of palm occurrence and density, suggesting a strong edaphic influence on the distribution of this group. Ecoregions with higher silt content in the soil showed the highest palm abundance and biomass, emphasizing the importance of pedological factors in structuring Amazonian plant communities. Together, the findings of these two chapters contribute to a more integrated understanding of the ecological patterns and environmental drivers that shape the diversity and abundance of trees and palms in the Amazon. They reinforce the importance of multiscale approaches and consideration of regional heterogeneity for the effective conservation of Amazonian biodiversity.