Using the eddy covariance technique, the Bowen-ratio meteorological and soil monitoring system, we analyzed the CO2 flux dynamics and its responses to temperature and moisture over a meadow wetland in the Horqin during the growing season (from May to September) in 2016. The results showed that the accumulated net ecosystem CO2 exchange (NEE) was -766.18 g CO2·m-2 during the growing season. The gross primary productivity (GPP) and ecosystem respiration (Re) were 3379.89 and 2613.71 g CO2·m-2, respectively. The ratio of Re to GPP was 77.3%, indicating that this ecosystem was an obvious carbon sink. The average diurnal variation of NEE exhibited a single peak U-shaped curve with an absorption of CO2 from May to mid August and a release of CO2 from late August to September. Daytime NEE well fitted with the photosynthetically active radiation (PAR) by a rectangular hyperbolic function. Meanwhile, the relationship was affected by the environmental factors, including vapor pressure deficit (VPD), soil water content (SWC) and air temperature (Ta). Regression analysis showed that the VPD and SWC for the maximum daytime NEE were 1.75 kPa and 35.5%, respectively. Daytime NEE increased with Ta, and with no inhibitory effect on the daytime NEE when it reached the maximum. Nighttime NEE had an exponential relationship with soil temperature (Ts). During the entire growing season, the temperature sensitivity of the ecosystem respiration (Q10) was 2.4, which was negatively related to SWC. The nighttime NEE was controlled by both Ts and SWC.
基于涡度相关和波文比气象土壤监测系统,研究了2016年科尔沁草甸湿地生态系统生长季5—9月CO2通量的动态变化特征,分析了温度、水分等环境因子与其的响应关系.结果表明:生长季累计净生态系统碳交换量(NEE)为-766.18 g CO2·m-2,总初级生产力(GPP)和生态系统呼吸量(Re)分别为3379.89和2613.71 g CO2·m-2,Re/GPP为77.3%,表现为明显的碳汇.NEE各月平均日变化呈单峰“U”型曲线,其中5—7月和8月中旬表现为吸收CO2,8月后半月和9月表现为释放CO2.日间NEE与光合有效辐射(PAR)呈显著的直角双曲线关系,同时受饱和水汽压差(VPD)、土壤含水量(SWC)和气温(Ta)等环境要素调控.回归关系表明,日间NEE达到最大时,VPD和SWC值分别为1.75 kPa和35.5%,而NEE随Ta增加逐渐增大,当Ta达到最大时,并未对NEE产生抑制作用;夜间NEE随土壤温度(Ts)呈指数趋势上升.在整个生长季,生态系统呼吸的温度敏感性指数(Q10)为2.4,且SWC越高,Q10越小,夜间NEE受Ts和SWC共同调控.
Keywords: Horqin; meadow wetland; moisture; net ecosystem CO 2 exchange; temperature.