Plant Species Diversity and Phytomass along an Altitudinal Gradient of Himalayan Rangeland of Eastern Nepal

The most important environmental driver is the elevation in mountain ecosystems. It strongly influences the distribution of species richness. Species richness is an indicator of the biological diversity and ecological condition of the area. To understand the status of phytomass, species diversity, and physico-chemical properties of soil along the altitudinal gradient and its influence on the interrelation between phytomass, species diversity, and physicochemical properties of soil. To know the correlation between plant species and environmental factors.We used a transect line method to enumerate the plant community in each sampling plot. Phytomass was estimated by the total harvesting method. Soil properties were determined with standard methods, viz., Blake and Hartge (1986), Chromic Acid Wet Oxidation Method, and Kjeldahl method. SPSS and R programming were used for data analysis.Plant diversity indices, viz., Shannon-Wiener diversity index, Simpson's dominant index, Pielou’s index, and Margalef index were highest at the low altitude and the lowest value at high altitude. AGB, BGB, SOC and STN were highest in high altitude (Jaljale). Phytosociological indices and environmental factors, except moisture and SBD, were high at high elevation. The first axis of ordination was positively correlated with SBD, moisture, ABG, and BGB and negatively with STN.The low-altitude rangelands have high anthropogenic activities; grazing, trampling, and burning disturbed the natural storage of organic carbon, nitrogen, phytomass, and diversity. The study showed a linear negative relationship between phytomass and altitude.