农垦与放牧对内蒙古草原N2O、CO2排放和CH4吸收的影响

利用优选静态箱/气相色谱法(GC),首次对我国内蒙古草原典型地区进行了人类活动对N₂O、CO₂和CH₄交换通量影响的实验观测结果表明,农垦麦田N₂O平均排放通量比原始草原高出3倍,并改变了草甸草原为CO₂汇的性质,使其季节排放净通量以C计增加14.3 mg·(m²·h).随放牧强度的增加CO₂排放通量呈线性增长,轻牧会引起草原对CH₄吸收的大幅增加,而随着放牧压力的增大,增加值迅速回落.农垦麦田与草甸草原相比地-气间CH₄交换无显著变化,放牧强度对N₂O排放影响无显著规律.土壤湿度和温度是影响草原排放N₂O和CO₂、吸收CH4季节变化形式的关键因子,而人类活动仅影响排放强度.排放和吸收量年际间差异很大,但主要受降水的影响.N₂O和CO₂排放与CH₄吸收峰值相反现象普遍存在.

Effects of Grazing and Cultivating on Emission of Nitrous Oxide, Carbon Dioxide and Uptake of Methane from Grasslands

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.