To understand carbon sequestration capacity of grasslands, the changes of CO2 flux in Xilinhot grasslands and the influence of environmental factors were analyzed by using the eddy data of Xilinhot National Climate Observatory in 2018-2021, and the distribution of flux source areas was analyzed. The results showed that the southwest wind prevailed in the study area throughout the year, the source area in the growing season was larger than that in the non-growing season, and the source area under stable atmospheric conditions was larger than that under unstable conditions. The maximum length of source region with a contribution rate of 90% was close to 400 m, which was consistent with the length estimated by the classical law. The net ecosystem exchange (NEE) of Xilinhot grasslands had obvious diurnal and seasonal dynamics, which was manifested as a carbon sink in the daytime and a carbon source at night during the growing season and weak carbon source in the non-growing season. From 2018 to 2021, the annual total NEE were -15.59, -46.28, -41.94, and -78.14 g C·m-2·a-1, respectively, with an average value of -45.49 g C·m-2·a-1, indicating that Xilinhot grassland had strong carbon sequestration capacity. Vapor pressure deficit and photosynthetically active radiation helped grasslands absorb atmospheric CO2. At night, when temperature was above 0 ℃, the increases in air and soil temperature promoted vegetation respiration to release CO2.
为探究草原生态系统固碳能力,利用锡林浩特国家气候观象台2018—2021年的涡动相关资料分析了锡林浩特草原生态系统CO2通量的变化特征以及环境因子对CO2通量的影响,并对通量源区分布进行了探讨。结果表明: 研究区全年盛行西南风,生长季的源区面积大于非生长季,大气稳定条件下的源区面积大于不稳定条件;90%贡献率的源区最大长度接近400 m,与经典法则估算的长度一致。锡林浩特草原净生态系统碳交换量(NEE)具有明显的日变化和季节变化,生长季白天为碳汇,夜间为碳源,非生长季白天和夜间均为弱碳源。2018—2021年,年总NEE分别为-15.59、-46.28、-41.94和-78.14 g C·m-2·a-1,平均值为-45.49 g C·m-2·a-1,表明锡林浩特草原有较强的固碳能力。饱和水汽压差和光合有效辐射有助于草原生态系统吸收大气中CO2;夜间,当温度高于0 ℃时,气温和土壤温度升高会促进植被呼吸作用释放CO2。.
Keywords: environmental impact factor; footprint; grassland ecosystem; net ecosystem exchange.