Patterns in Species Composition and Distribution Among Vascular Epiphytes in Low-Lying Semi-Evergreen Forests of Arunachal Pradesh, India

Abstract

The patterns in epiphyte species composition and distribution in the low-lying semi evergreen forests was studied in Pakhui Wildlife Sanctuary and the adjacent Doimara Reserved Forests in western Arunachal Pradesh. Epiphyte community changes due to microclimate and host characteristics were studied by comparing sites of different microclimates namely riverbanks, tree fall gaps, closed forests and logged forests. Systematic sampling showed that epiphyte species diversity, increased marginally from low levels in the tree fall gaps to maximum levels in the riverbanks with intermediate levels in the logged forest and closed forest. There were dominance of certain families and life forms in different sites. Trends in epiphytic communities were closely related to changes in microclimate and host characters. The environmental variables were summarized by Principal Component Analysis, which yielded three components explaining 75.5% of the variance. Component one was positively correlated with temperature and canopy cover and light intensity in the horizontal zone, whereas relative humidity was negatively correlated. Component two was strongly correlated with vertical light intensities. Component three was purely a temperature factor . Araceae, Gesneriaceae and Asclepiadaceae correlated with vertical temperature humidity component while Orchidaceae and Moraceae were correlated with horizontal temperature. Families Aspleniaceae and Gesneriaceae were positively correlated with component one (qualitative parameters) of the vegetation characteristics, Therefore, epiphyte species richness were significantly different between across bark texture and architectural model of the host. Warty and wrinkled bark supported maximum species and Champagnats model of tree architecture supported higher number of epiphyte species. Six species were found only in the trunks and ten species confined themselves to branches. A total of twelve rare species of different families were found in the study area. The major implications of the study are the intimate relationship of epiphytes with diverse factors of climate and host characters, the change in one will trigger corresponding changes in other. Logging as a practice removes lot of trees, which reduces the diversity of substrate and microhabitat conditions available for epiphytes. It is important to maintain atleast a few big trees to serve as mother trees for recovery of the lost species.