Effects of grazing and fencing on Stipa purpurea community biomass allocation and carbon, nitrogen and phosphorus pools on the northern Tibet Plateau alpine

The “grassland enclosure project” is an important measure to improve ecological and environmental quality of degradation grassland and promote economy sustainable development of pastoral area. In the present study, the Stipa purpurea community biomass allocation and carbon(C), nitrogen(N) and phosphorus (P) pools were investigated in three utilization management blocks including free grazing grassland (FG), four years enclosed grassland(F4) and eight years enclosed grassland (F8) on the northern Tibet Plateau alpine. The results showed that aboveground biomass of S. purpurea community in FG, F4 and F8 were 46.12, 146.40 and 256.44 g·m-2, respectively. Root biomasses in layer of 0-15 cm were 274.74, 214.87 and 764.59 g·m-2 and root biomasses in layer of 15-30 cm were 17.80, 17.56 and 31.64 g·m-2 for these three treatments, respectively. These results suggested that enclosure significantly increased (P<0.05) the community growth. S. purpurea and Carex moorcroftii had the highest biomass in F4 (P<0.05). Enclosure significantly increased plant C, N and P pools of S. purpurea community and F8 had the highest nutrient pools (P<0.05) among the three blocks. Our research provide basic data for revealing plant biomass and nutrient allocation response to grassland utilization management and evaluating ecological effects of “grassland enclosure project”.