Species Richness Across the Forest-Line Ecotone in Central Himalayan Landscape of Nepal

Abstract

With the main objective of exploring the species richness and composition in forest-line ecotone together with altitudinal pattern in different slope aspect (north and south) this research was done in the transitional zone (Ecotone) of forest to non-forest landscape of Central Himalaya (Langtang) Nepal. Data were collected from 27 plots in the northern aspect and 21 plots in the southern aspect of 10m × 10m (altogether 48 plots combining both the aspect). Qualitative and quantitative analysis of environmental variables and disturbance indicator were also recorded in each sampling plot. Altogether 83 species and 93 species of vascular plants were recorded in the north and south aspect respectively. The data thus obtained were analyzed by using ordination technique, Canonical Correspondence Analysis (CCA), Detrented Correspondence Analysis and Regression Analysis. Major factors related to variation in species richness were altitude, canopy cover and slope. With the increase in altitude species richness was found to decrease in the southern aspect whereas, there was slight increase in species richness near above the forest-line in northern aspect. Mean species richness between the forest and open landscape of northern aspect indicated no significant differences. On other hand, compared to northern aspect there was a significant difference in southern aspect with forest plots having higher species richness. Though, grazing not being highly significant in both the aspect species richness was found to be high in the grazed plots of northern aspect due to moderate grazing and comparatively lower in the southern aspect due to high human intervention and grazing pressure. Species richness trend was found to be decreasing with the increase in slope in both the aspect due to high water runoff, unstable soil condition and rocky patches found on the steep slope of the study area.