Effects of Grazing and Cultivating on Emission of Nitrous Oxide, Carbon Dioxide and Uptake of Methane from Grasslands
农垦与放牧对内蒙古草原N2O、CO2排放和CH4吸收的影响

Measurement of N2O, CO2 and CH4 with the optimized closed chamber/GC technique in the typical grassland, which were influenced by human activities, grazing and cultivating first time in situ were carried out in Inner Mongolia of P. R. China from 1998 to 1999. It was found that wheat cropping can increase N2O production 3 times than the native, and changed a CO2 sink of Inner Mongolia Steppe to a significant source, increased efflux CO2 (C)average 14.3 mg·(m2·h)-1 from Jun. to Dec. in 1998. CH4 uptake was highly increased if there was grazing lightly. There were no effects of wheat cropping on CH4 uptake and no significant results of grazing on N2O emission. Soil moisture and temperature were the key factors ,other than human activities, which affect the patterns of seasonal variation of N2O and CO2 emission and CH4 uptake. Highly inter annual variations,which resulted from the annual precipitation, of the exchange fluxes and seasonal variation patterns of N2O and CO2 emission and CH4 uptake there were. It was a fact that N2O and CO2 emission from the soils was inversely related to CH4 uptake.