Consequências ecológicas da fragmentação florestal na amazônia

Abstract

*[Many studies have analyzed the ecological consequences of forest fragmentation on Amazonian forests & the results of these studies are summarized here. Habitat fragmentation has extensive effects on Amazon rainforests, affecting diversity & community composition in the resulting fragments, & also affecting ecological processes like pollination, nutrient cycling, & carbon fixation. The ecological changes resulting from fragmentation are generally of inverse proportional magnitude to the size of the fragment area. Consequently, smaller fragments are usually less species-rich & have fewer species per area than do larger forest fragments. Forest fragments in the Amazon seem to be particularly prone to edge effects. Fragmentation dramatically increases edges of tropical forests: new edges are artificial & abrupt, forming a stark boundary between the forest & the surrounding, altered landscape. One of the most striking effects is a dramatic increase in the mortality of trees, leading to increased canopy-gap formation. Edge effects in the fragments also alter physical gradients & species abundances. In general, species that are most vulnerable to fragmentation tend to respond negatively to edges, have large area requirements, and/or are intolerant to the surrounding 'matrix' (= the mosaic of modified habitats around the fragments), whereas species that are resilient to fragmentation usually have an opposite set of characteristics.]