北京八达岭林场人工林净碳交换及其环境影响因子

Net carbon exchange and its environmental affecting factors in a forest plantation in Badaling,Beijing of China

2011年11月-2012年10月，采用涡度相关法对北京市八达岭林场4年生针阔混交人工林的碳交换特征进行了连续观测．结果表明：观测期间，该森林生态系统在7、8月为碳汇，其余月份均为碳源，净碳释放量与吸收量分别在4月和7月达到最大．生态系统净生产力为（-256±21）gC·m-2·a-1，其中生态系统呼吸为（950±36）gC·m-2·a-1，总初级生产力为（694±17）gC·m-2·a-1．生态系统呼吸与10cm深度土壤温度呈较好的指数关系，其温度敏感性系数（Q10）为2．2．在5-9月，白天生态系统净碳交换对光合有效辐射的响应符合直角双曲线方程，表观量子效率呈明显的季节变化（0．0219～0．0506μmol CO1·μmol-1），生态系统最大光合速率和白天平均生态系统呼吸强度与光合有效辐射和温度的季节变化趋势相似．此外，7、8月饱和水汽压差与土壤含水量对白天生态系统净碳交换有显著的影响．

By using eddy covariance technique, a year-round （ November, 2011 -October, 2012） continuous measurement of net ecosystem carbon dioxide exchange （NEE） was conducted in a 4- year old mixed forest plantation in Badaling of Beijing. The forest plantation ecosystem was a net carbon sink in July and August, but a carbon source in the rest months. The monthly net carbon loss and uptake were the largest in April and July, respectively. The annual net ecosystem produc- tivity was （-256 ± 21 ） g C . m-2. a-1, in which, the ecosystem respiration was （950 ± 36） g C . m-2 . a-1, and the gross ecosystem productivity was （694±17） g C. m-2 . a-1 The night- time NEE increased exponentially with the soil temperature at 10 cm depth, with the estimated tem- perature sensitivity of ecosystem respiration （ Q10 ） being 2.2. During the growth season （ May-Sep- tember）, the daytime NEE increased with photosynthetically active radiation （PAR） as described by the Miehaelis-Menten rectangular hyperbola. The ecosystem quantum yield varied seasonally, ranging from 0. 0219 μmol CO2. μmol-1 in May to 0. 0506μmol CO2 .μmol-1 in July. The maxi- mum carbon assimilation rate and the average daytime respiration followed the seasonal trends of PAR and air temperature. In July and August, vapor pressure deficit and soil moisture played a sig- nificant role in determining daytime NEE.