Distribution of vascular plants and variation in plant functional traits along a subalpine-alpine gradient in Manang, Central Nepal

Abstract

A systematic investigation of vascular plant species distribution along a subalpine alpine gradient of Central Himalaya, Manang, Nepal along an elevation gradient ranging from 3700 m to 4600 m asl was carried out. Study aimed at identifying the diversity and distribution patterns of vascular plants, including different life forms and biogeographic groups along the gradient; and conceptualizing the inter- and intraspecific variation in plant functional traits (PFTs) with elevation. The species richness exhibited a hump-shaped pattern with elevation with maximum richness between 4200 to 4500 m asl, with major influence of shrub canopy, radiation, disturbance, and substrate types. Species composition varied between and within the elevation band in different canopy types, including shrub shelter and open canopy. Life form analysis revealed that the study area was characterized by harsh climate with majority of taxa belonging to chamaephyte and hemicryptophyte. However, substrate type played a very important role in determining the presence of particular life form along the gradient. Biogeographically, majority of taxa were Himalayan endemics followed by the species with pan-Himalayan distribution. The proportion of Himalayan endemics increased with increasing elevation. The species indicator to the study site were mostly herbaceous taxa with biogeographical distribution restricted to the Himalaya, indicating the importance of endemics in shaping the alpine vegetation of the study area. A complete turnover of indicator species along elevation gradient was observed due to distinct phytoclimate. The presence of distinct phytoclimate resulted in inter- and intraspecific variation in different PFTs along the elevation gradient. For the analysis of PFTs, Rhododendron lepidotum, Cotoneaster microphyllus, Dactylorhiza hatagirea, Cypripedium himalaicum, and Rhodiola bupleuroides were considered. The analysis of PFTs showed that different plant species respond differently in terms of their PFTs with increasing elevation and the variation in PFTs is species specific and trait specific. The mountain ecosystems are sensitive to climate therefore the underlying ecological processes influencing the PFTs may change dramatically under climate change. Therefore, the study of variation in PFTs along a natural gradient like elevation is an effective method to understand how a species or, the community as a whole change with a variety of environmental conditions and how they respond to climate change.