Influência de parâmetros locais e da paisagem sobre comunidades de epífitas vasculares em pastagens

Abstract

Vascular epiphytes are an important and diverse plant assemblage in tropical rainforests and it accountings for about 10% of all world flora. Due to their aerial condition they are particularly sensitive to the effects of environmental modifications caused by anthropogenic activities such as forest fragmentation. However, despite the importance of this plant group and the extension of areas of agricultural activity very little is known about the occurrence of epiphytes in isolated trees in pastures and the influence of the surrounding landscape. Our objective was to investigate the effect of 20 environmental variables at local and landscape (400,700, and 1,000m) scales on the richness, abundance, and biomass of vascular epiphytes and number of phorophytes in isolated pasture trees. We sampled all angiosperm holoepiphytes in trees with DBH ≥ 5cm within plots of 1.96 ha each along 15 areas. In order to test the effect of local and landscape metrics on community attributes we used generalized linear models (GLM’s). We model the responses of the total epiphytic community (all species) and functional groups of dominance, pollination, and dispersion. We recorded 16 epiphytic species and 9,936 individuals of vascular epiphytes. Together the dominant species Tillandsia recurvata and Tillandsia pohliana accounted for 84% of the total abundance recorded. Most of species were classified as entomophilous and anemochorous. There was no influence of local scale (pasture) metrics on any response. On the other hand, the landscape composition (% pasture, %forest, %coffee and cover land use richness) affected different responses of the communities (abundance, biomass, richness and %phorophytes) at different scales (400m and 1000m). Our results point to the importance of pasture as a refuge for epiphytic communities in fragmented landscapes and for the influence of the heterogeneity of the agricultural landscape on the maintenance of this group. It also provides important methodological implications being the first study to adopt simultaneously different forms of quantification and division of species into functional groups and to evaluate the influence of variables multi-scales.