Effects of Grazing on Carbon Dioxide and Methane Fluxes in Typical Temperate Grassland in Inner Mongolia, China
放牧对温带典型草原含碳温室气体CO2、CH4通量特征的影响

Using the static chamber method, the fluxes of carbon dioxide and methane of soil were measured through the continuous experiment in situ from July 2001 to July 2003 in Aneurolepidium Chinense and Stipa grandis fence-enclosed non-grazing grasslands and their corresponding grazing pastures in Xinlin river basin of Inner Mongolia in China. According to the results of field experiment, the fluxes characteristics and seasonal variation patterns of two non-grazing grasslands and their grazing grasslands were compared. The results indicated that: 1) Comparing with the native fence-enclosed communities, the grazing didn't changed the direction of sources and sinks and the seasonal variation patterns of the carbon dioxide and methane fluxes; 2) The average emission fluxes of carbon dioxide at different statistical period from 2001 to 2003 in Aneurolepidium Chinense fence-enclosed grassland were 9.6 percent to 67.7 percent higher than that of Aneurolepidium Chinense rotational grazing grassland and 22.7 percent to 59.4 percent higher in Stipa grandis fence-enclosed grassland than that in the Stipa grandis free-grazing grassland. While in non-growing season, the differences between fence-enclosed grasslands and corresponding rotational or free grazing grasslands weren't significant; 3) The annual CH_4 uptake fluxes of grazing grasslands were lower than those in corresponding fence-enclosed grasslands, the grazing decreased the soil sink intensity of CH_4. But the difference of annual or growing-season average CH_4 fluxes between fence-enclosed and grazing grasslands didn't reached the significance level of 0.05. The drought has narrowed the difference between them; 4) The grazing promoted the CH_4 uptake intensity of soil in growing season, while also promoted the emission fluxes of CH_4 in certain period of non-growing season especially during the period of freezing-thawing, the grazing enlarged the annual variation range of CH_4 fluxes.