Elevational and phytophysiognomic gradients influence the epiphytic community in a cloud forest of the Atlantic phytogeographic domain

摘要

Biological communities vary in composition and structure according to changes in the environment, such as in mountainous areas where temperature and moisture change with elevation, leading to gradual changes in vegetation. The altitudinal gradient is considered minors of the latitudinal gradient, although the richness peak can occur in the middle of the gradient, due to the greater total availability of moisture and/or due to the mid-domain effect. We aimed to test whether there was an intermediary peak in the richness of vascular epiphytes in two environmental gradients represented by elevation (around 1200-1700 m.s.m.) and by three subphysiognomies of cloud dwarf-forest in the Brazilian Atlantic Forest. For this purpose, 24 plots of 10 x 20 m were established and divided into eight sets in each subphysiognomy, along the altitudinal gradient. The community structure was analyzed by calculating the Shannon diversity index (H') , the Pielou uniformity index (J), and taxonomic diversity indices (Delta(+) and Lambda(+)). In total, 568 phorophytes were sampled, resulting in 3771 occurrences of epiphytes, distributed in 146 species. The diversity was different between the physiognomies of dwarf-forest and along the elevation gradient, and was specifically greater with higher elevation. The value of Delta(+) was lower than expected in one plot, and represented a potential human impact. The obtained results highlight the diversity of this region and the important contribution of the epiphytes, as well as the sensitivity of epiphytic communities to the different vegetation physiognomies and the climatic variations caused by the elevation.