Aboveground biomass and concentration of nutrients in semiarid rangeland plant species: Influence of grazing and soil moisture

Spatial and temporal patterns of aboveground biomass and nutritive value of rangeland species with respect to the influence of grazing and soil moisture were investigated. The research was conducted during two years at the Tomagh Research Station, near Sanjawi, Ziarat District, Balochistan, Pakistan. This area is protected from grazing since 1998; however, some of the area is open for grazing. Three sites were selected for research purposes: a protected plain, a protected hilly, and an unprotected plain grazed area. Sampling was carried out during the spring, summer and autumn seasons. Results revealed that soil moisture was greater at the protected than unprotected sites. The aboveground plant biomass was 66% to 76% lower at unprotected than protected sites. The biomass of annual plant species was nearly 0 at grazed sites. Species differed in their nutrient concentrations, but these were similar among protected and unprotected grazed areas. Our findings indicate lower nutrient use efficiency at grazed than ungrazed, protected sites. Eleven years of protection from grazing increased significantly plant biomass, enhanced their nutrient use efficiency and allowed growth of annual plant species.