Vascular plant diversity along an elevational gradient in the Central Himalayas, western Nepal

Elevational gradients are linked with different abiotic and biotic factors, which in turn influence the distribution of plant diversity. In the present study we explored the relative importance of different environmental factors in shaping species diversity and composition of vascular plant species along an elevational gradient in the Chamelia Valley, Api-Nampa Conservation Area in western Nepal. Data were collected from 2,000 to 3,800 m above sea level and analysed using a generalized linear mixed model (GLM) and non-metric multidimensional scaling (NMDS). We recorded 231 vascular plant species consisting of 158 herb species belonging to 55 families, 37 shrub species belonging to 22 families and 36 tree species belonging to 23 families. Species richness and species abundance significantly decreased with increasing elevation. However, species richness increased with the intensity of vegetation cutting. Species richness and abundance also increased with increased annual precipitation and mean annual temperature whereas species abundance decreased with grazing, soil phosphorus and nitrogen. NMDS ordination revealed that mean annual temperature and annual precipitation affect the composition of vascular plant species in opposite ways to elevation. Among the many anthropogenic disturbances, only grazing affected species composition. In conclusion, more than one environmental factor contribute to the shaping of patterns of vascular plant species distribution in western Nepal. Knowledge on species diversity, distribution and underlying factors needs to be taken into consideration when formulating and implementing conservation strategies.