农垦对草甸草原生态系统温室气体(CH_4和N_2O)的影响

2012~2013年在呼伦贝尔谢尔塔拉牧场对天然草甸草地和草地开垦农田后,不同农作物种植和管理措施下甲烷(CH4)和氧化亚氮(N2O)排放进行了野外实地观测.结果表明,天然草甸草地和农田均为大气CH4的吸收汇、N2O的排放源.在生长季,天然草甸草地开垦增强了土壤的N2O排放量,但是对土壤CH4通量的影响却存在较大的不确定性.在相同的气象条件下,作物类型对生长季农田CH4和N2O排放通量都没有影响.在生长季,灌溉对干旱农田的CH4平均吸收通量没有显著影响,但降低了干旱农田N2O的平均排放通量.2012年和2013年农田CH4和N2O的差异主要是因为降雨量不同导致的年际差异.回归分析表明,N2O排放通量与土壤湿度呈线性相关,与土壤温度没有相关性,CH4的吸收通量与土壤温度呈线性相关,与土壤湿度呈线性负相关.土壤湿度是影响土壤CH4吸收和N2O排放的主要因素.

Effect of reclamation on greenhouse gases (CH4 and N2O) fluxes in meadow-steppe ecosystem

The soil CH4 and N2O emission fluxes from the natural meadow-steppe grassland and reclaimed grassland under different crop planting and management measures were investigated during the growing seasons in 2012 and 2013 at Xieertala pasture, Hulunber, Inner Mongolia. The results showed that both the natural grassland and reclaimed grassland played a role as a sink for CH4 and a source for N2O. The conversion of natural grassland to cropland increased N2O emissions from the soil in growing seasons, however, there was a large uncertainty in the impact on soil CH4 fluxes. There was no difference in CH4 and N2O emission fluxes for different crop types under same meteorological conditions. Irrigation had no clear effect on CH4 average uptake fluxes in growing seasons, but significantly reduced N2O average emission fluxes. The differences in CH4 and N2O fluxes for 2012 and 2013 were mainly caused by the inter-annual precipitation variability. The correlation analysis and stepwise linear regression revealed that the soil CH4 and N2O emission fluxes were significantly correlated with soil moisture, the CH4 fluxes were also in linear relationship with soil temperature.