温带草原生态系统CO_2排放对环境因子变化的响应

Response of CO2 Emissions to the Change of Major Environmental Factors in Temperate Grassland Ecosystem

2001年6～9月,在内蒙古地区气候异常干旱的条件下(降水量不到历史正常年份的1/6),利用静态暗箱法分别对锡林河流域草甸草原、羊草草原、大针茅草原等典型温带草原生态系统的CO2排放状况及主要环境因子进行了实地观测,分析它们之间的相关性。结果表明,在草原群落活跃生长期内,CO2排放通量的月变化对气温和地温的响应都不明显;但CO2日变化与气温和地表温度呈显著正相关,与5、10cm处的地温相关不显著;从CO2排放的平均值来看,草甸、羊草、大针茅草原样地随降水梯度变化(年降水量递减),CO2的排放通量依次分别由268.7、211.6、181.4mg·m-2·h-1递减,说明大气降水是影响CO2排放通量变化的重要环境因子。此外,CO2排放通量还与土壤水分、土壤有机质、土壤全氮含量呈正相关关系。

Using static dark enclosed chamber technique, the fluxes of CO2 from temperate grassland such as meadow, Leymus chinensis grassland and Stipa grandis grassland and their major environmental factors were measured in Xilin River Basin of Inner Mongolia under the abnormally dry circumstances from June to September in 2001(rainfall was less than 1/6 of that in historical normal years). Then the correlation between the emissions of CO2 and major environmental factors were studied. The results showed that there was a little or no correlation between the monthly fluctuation of the emissions of CO2 from grassland and air temperature and topsoil temperature during the period of rapid growth of grassland, however the daily variation of CO2 flux was significantly positively correlated with the earth’s surface temperature and air temperature. And the relation between the emissions of CO2 and soil temperatures at the depth of 5 cm and 10 cm was not obvious. As for the response of the fluxes of CO2 to annual precipitation, the average emissions of CO2 dropped off from 268.7, 211.6 to 181.4 mg?m-2?h-1 in meadow, Leymus chinensis grassland and Stipa grandis grassland, respectively. That meant precipitation was an important environmental factor influencing the fluxes of CO2 from grassland. It was also found that there was a close and positive correlation between the emission of CO2 and other environmental factors such as soil water content, organic content and total nitrogen content in different soil layers.