半干旱草原温室气体排放/吸收与环境因子的关系研究

Study on Relationship between the Variations of Greenhouse Gases Efflux/ Uptake and the Key Environmental Factors in Mongolia Semi-Arid Grasslands

静态箱-气相色谱法对内蒙古半干旱草原连续两年的实验观测研究结果表明,内蒙古草原是大气CO2和N2O的排放源,而是CH4的汇。在植物生长不同季节,草原生态系统排放/吸收温室气体CO2、CH4和N2O的日变化形式各有不同,其中在植物生长旺季日变化形式最具特征。3种温室气体的季节排放/吸收高峰主要出现在土壤湿度较大的春融和降雨较为集中时期。所有草原植物生长季节CO2,净排放日变化形式均为白天出现排放低值,夜间出现排放高值。较高的温度有利于CO2排放,地上生物量决定着光合吸收CO2量值的高低。影响半干旱草原吸收CH4和排放N2O日变化形式的关键是土壤含水量和供氧状况,日温变化则主要影响日变化强度。吸收CH4和排放N月潭O的季节变化与土壤湿度季节变化分别呈线性反、正相关,相关系数均在0.4～0.6之间。自由放牧使CO2、N2O和CH4交换速率日较差降低,同时使N2O和CH4年度排放/吸收量减少和CO2年度排放量增加。

Static chamber-gas chromatographic techniques were used for measuring efflux/ uptake of CO2, CH4 and N,O in Inner Mongolia semi-arid typical grasslands. Our data indicates that Ihe Inner Mongolia semi-arid grassland represent a significant global source of CO, and N,O, and a significant sink of CH4. There are different patterns of diurnal variations in different season, but the most significant pattern is in summer time or early fall. The most intensive seasonal efflux/uptake of CO2. CH4 and N2O occurs when the soils much wetter for raining or spring-melting. There is a general diurnal variation pattern on CO2 efflux, the efflux is low during the day while the efflux is high in the late evening. The higher the temperature is, the higher the efflux of CO2 occurs; the more prosperous the biomass above the ground is, the higher the uptake of CO2 occurs. The diurnal variation patterns of CH4 and N2O are controlled by the key factors that are soi! moisture and the capacity of transporting oxygen, the range of diurnal uptake/emission flux of CH4 and N2O depends on the variation of diurnal temperature. The significant positive/ negative correlation were found between the seasonal va nation of efflux/ uptake of N2O/ CH4 and the variation of tempera ture(r = 0.4- 0.6). Diurnal range of efflux / uptake of N2O / CH4 decreased for free grazing in Inner Mongolia grasslands, simultaneity, the quantity of annual efflux / uptake of N,O / CH4 decreased either, while the annual efflux of CO, increased.