Species Composition and Diversity Pattern in various Grassland Communities with Respect to Different Disturbance and Light Regimes

The grassy landscape of north-eastern Uttar Pradesh showed quite high species richness and a total of 287 plant species belonging to 183 genera under 53 families were encountered within the sampled communities. We categorized each of 31 locations under 12 disturbance types under two light regimes. Their effects were observed in relation to different diversity attributes of grassland communities. In general, the number of species and genera was much greater in open condition as compared to that under partial shade condition. Approximately, >55% herbs, 55.5% shrubs and 50% climbers were common to both the light conditions. Over 31% herbs were common under open and >39.54% under partial shade condition at all the three disturbance levels. Nearly 14.28% species were common to all the disturbance level under open condition. In both, open as well as partial-shade conditions, the grassland communities were significantly different in terms of species richness, diversity, dominance and evenness with respect to three different levels of disturbance. The mean value of species richness, diversity and evenness were maximum in partially shaded communities as compared to open communities. The diversity and evenness were higher in moderate level of disturbance under both the light conditions except species richness. Our results also support Intermediate Disturbance Hypothesis (IDH) as the communities facing moderate level of disturbance showed high species diversity. A few species like Astercantha longifolia, Cassia absus, Euphorbia hypercifolia, Evolvulus alsinoides, Leucas cephalotus, Perotis indica and Teramnus labialis which were quite uncommon to general grassy landscape were encountered in communities facing low disturbance. Our analysis showed that the moderate level of disturbance in the form of grazing, trampling and cutting are necessary to maintain optimum species diversity. Nevertheless, the degree of exposure did affect the species richness and diversity pattern of the community.