Plant Species Richness and Diversity Patterns along Elevation Gradient in Shaskouh Protected Area, South Khorasan

A fundamental characteristic of mountain ecosystems is the drastic change in vegetation along elevation gradient that promote the diversification of plant species. The aim of this study is investigation of plant species richness and diversity patterns along elevation gradient in mountainous environments of Shaskouh Protected Area, South Khorasan Province. Vegetation sampling was conducted in five elevation zones (1200-1000, 1500-1200, 2000-1500, 2500-2000 and 2850-2500 meters above sea level). Abundance distribution models, numerical indices of species diversity, richness, dominance and evenness were determined for each zone. Also, to ordination the species composition along the elevation gradient, Detrended Correspondence Analysis (DCA) was used. The results showed that in mountain environments, elevation gradient has significant effect (p≤0.01) on plant species diversity and richness. Maximum species richness (27 taxa) were observed at low elevation (1500-1200 meters above sea level) and minimum species richness (10 and 7 taxa) were found in the moderate classes of elevation (2000-2500 meters above sea level) and the high classes of elevation (2500-2850 meters above sea level). As well as, the results showed that species diversity was low at low elevations, then with increasing elevation reaches its maximum at middle elevation, then decreases at high elevations (above 2500 meters above sea level).