草原土壤的碳氮分布与CO2排放通量的相关性分析

利用静态暗箱法,对内蒙古锡林河流域的贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、克氏针茅(Stipa krylovii)等草原群落样地的CO₂排放通量进行了测定;同时采集各样地的不同层次土壤混合样,分析其中有机碳和全氮的含量,探讨其与CO₂排放的相关性.结果发现:不同样地群落的CO₂排放与其土壤中不同层次的有机碳和全氮含量呈高度正相关,相关系数(R)均0.8以上,说明在环境因子相对稳定的情况下,土壤有机碳和全氮含量直接或间接地决定生态系统CO₂排放通量的变化.另外,土壤不同层次的有机碳和全氮含量随深度增加递减,其中70%以上集中在0～30cm土层中,说明它们主要是来自地表有机质的分解;在0～100cm的土层中,土壤有机碳和全氮的总含量从贝加尔针茅草原、大针茅草原、羊草草原和克氏针茅草原依次减少,表明降水量、蒸发量和干燥度是影响土壤有机碳、全氮分布的重要因子.

Analyses of the Correlation Between the Fluxes of CO2 and the Distribution of C & N in Grassland Soils

Using static dark enclosed chamber technique, the emissions of CO2 from typical temperate grasslands such as Stipa baicalensis, Leymus chinensis, Stipa grandis and Stipa krylovii in Xilin River Basin of Inner Mongolia were measured. And the contents of organic carbon and total nitrogen in different soil layers were also studied to analyze the correlation between the emissions of CO2 and the contents of C & N. The results showed that the emissions of CO2 from the 4 grassland communities were significantly positively correlated with soil organic carbon and total nitrogen in different layers of grassland soils, and the correlation coefficients were almost all above 0.8. That meant the flux of CO2 is severely influenced by the contents of soil organic carbon and total nitrogen when environmental factors were similar. The decreases of soil organic carbon and total nitrogen with the depth into soils (more than 70% of the contents centralizes above 0-30 cm layer) showed that most of them came from the decomposition of organic matter on the earth's surface. In the 0-100 cm layer of grassland soils, the decreases of amount of soil organic carbon and total nitrogen from Stipa baicalensis, Stipa grandis and Leymus chinensis grasslands to Stipa krylovii grassland orderly showed that the impacts of precipitation, evaporation and dryness index on the distribution of soil organic carbon and total nitrogen were important.