Effect of summer grazing intensity on GHG emission in the North Tibet steppe

A grazing intensity experiment was conducted to investigate the effect of summer grazing intensity on GHG emission in the North Tibet steppe dominated by Stipa purpurea through measuring CO2, CH4 and N2O emission with static chamber method. This study indicated that CO2 emission from the S.purpurea steppe increased with the increase of grazing intensity when the grazing intensity was moderate, and it decreased when the grazing density was heavy grazing density. The increase of grazing intensity significantly decreased the absorption of S.purpurea steppe for CH4 (P0.05), but it did not affect the steppe function as a sink of CH4. Lightly grazing intensity had no significant effect on N2O emission of the S.purpurea steppe. However, N2O emission significantly increased when the grazing density was over middle grazing density (P0.05). In this study, the global warming potential (GWP) was used to estimate the total GHG emissions of alpine steppe, the CO2 emissions accounted for nearly 98% of the total emissions, and the CH4 absorption and N2O emission only accounted for 1%, respectively, and their amount was trade off.