Efeitos da fragmentação florestal sobre o estabelecimento de quatro espécies arbóreas em florestas de terra-firme na amazônia central

Abstract

The Amazon basin maintains the largest proportion of tropical forests in the world. However, this region has been suffering with high rates of deforestation and habitat fragmentation. Forest fragmentation can affect either positively or negatively the persistence of tropical tree species some species can increase their densities whereas other species can diminish or even to be locally extinct. Here we tested for the effects of forest fragmentation on the establishment of two canopy species (Eschweilera coriacea and Scleronema micranthum) and two understory species (Helianthostylis sprucei and Rinorea racemosa). The study area is the Biological Dynamics of Forest Fragments Project, in central Amazon, Brazil (2°30 S, 60°O). We compared mortality and recruitment rates of individuals ≥ 10 cm DBH between forest edge and interior sites and among different forest fragment sizes and the density of smaller individuals 1.0-9.9 DBH between edge and interior. While R. racemosa showed high recruitment rate and greater density of smaller individuals in fragmented areas, H. sprucei showed high mortality rate and lower density of small individuals. The canopy species E. coriacea apparently does not respond to the changes occurred from the fragmentation processes. In contrast, demography and population structure of S. micranthum was changed in fragmented areas. For this species, both mortality and recruitment rates were higher in fragmented areas, while the density of small trees was similar between fragmented and continuous areas. The results of this study show that forest fragmentation can lead to differentiated effects in the establishment and demography of tree species and that all tree species life stages should be considered to effectively assess the effects of fragmentation on plant populations. Moreover, these findings suggest that life history and demographic traits of each species, rather than the position that a species occupies in the canopy, determine the susceptibility of a species to forest fragmentation