SPECIES RICHNESS, ETHNOBOTANICAL SPECIES RICHNESS AND HUMAN SETTLEMENTS ALONG A HIMALAYAN ALTITUDINAL GRADIENT: PRIORITIZING PLANT CONSERVATION IN PALAS VALLEY, PAKISTAN

This study explores the distribution pattern of species richness and ethnobotanically important plant species richness along an altitudinal gradient in Palas valley, Pakistan. The data related to species' occurrences were derived from field GPS surveys from 2004 to 2007, while settlement data were obtained from Google Earth T. The altitudinal information, based on locational data of species and settlements, was extracted from a 30 m resolution digital elevation model (DEM) using a geographic information system (GIS). Species richness and number of houses were then determined for 100 m altitudinal intervals and tested as response variables against altitude (independent variable) to explore their possible relationships using scatter plots and quadratic regression. The species richness was found to follow a bell-shaped distribution (R-2=0.87) with a maximum near mid-altitudes. The greatest species richness was attained between 2400-3200 m a.s.l (above sea level) and ethnobotanically important species richness was highest between 2500-2800 m a.s.l. (R-2=0.93). There was a highly positive correlation (r=0.88) between species richness and ethnobotanically important species richness. The majority of settlements were distributed between 20002400 m a.s.l. (R-2=0.47). The highest overall plant species richness, as well as ethnobotanically important species, is thus attributed to altitudes adjacent to but higher than the permanent settlements (2400-3200 m a.s.l.). Considering the valley as an important species rich area within its neighborhood, the localities in mid-altitudes (2400-3200 m a.s.l.) should be considered as major sites to be managed for the sustainable harvest of local plant resources and for plant conservation in a regional context.