Dinâmica de Comunidades Arbóreas em Áreas Expostas ao Desmatamento na Amazônia Brasileira

Abstract

The Amazon basin strongly influences the global carbon cycle, storing billions of tonnes of carbon in a relatively small number of ‘hyperdominant’ tree species. However, the Amazon carbon stock is threatened. Forests are being cleared and fragmented, with trees near forest margins subjected to various physical and biotic edge effects that can alter plant survival and growth. We investigated the occurrence of hyperdominant tree species in the Brazilian Amazon between 1988 and 2021, to assess how edge effects influence tree mortality and carbon storage. Using plot and herbaria data, we found 22% of tree occurrence records in deforested areas, 35% within 1 km of the forest edge, and 43% in continuous forest. At the local scale in central Amazonia, tree monitoring data over 30 years also showed that forest fragments had twice the mortality rate of continuous forests due to edge effects. Although trees in fragments had higher initial growth, this pattern declined over the years and eventually resulted in significant carbon loss, mainly from tree mortality. Edge effects have led to annual declines in the biomass of forest remnants, suggesting that hyperdominant species are also susceptible to disturbances that lead to degradation and forest losses. Conservation of the Amazon forests requires an approach that considers the effects of local disturbances on carbon stocks in the region.