二氧化碳储存通量对森林生态系统碳收支的影响

涡度相关系统观测高度以下的CO2储存通量对准确评价森林生态系统与大气间净CO2交换量(NEE)有着重要的影响.本研究以长白山阔叶红松林为研究对象,利用2003年的涡度相关观测数据以及CO2浓度廓线数据,分析了CO2储存通量的变化规律及其对碳收支过程的影响.结果表明:涡度相关观测高度以下的CO2储存通量具有典型的日变化特征,其最大变化量出现在大气稳定与不稳定层结转换期.利用涡度相关系统观测的单点CO2浓度变化方法与利用CO2浓度廓线方法计算的CO2储存通量差异不显著.忽略CO2储存通量,在半小时尺度上会造成对夜间和白天的NEE分别低估25%和19%,在日和年尺度上,会对NEE低估10%和25%;忽略CO2储存通量,会低估Michaelis-Menten光响应方程及Lloyd-Taylor呼吸方程的参数,并且对表观初始量子效率α和参考呼吸Rref的低估最大;忽略CO2储存通量,在半小时、日及年尺度上,均会对总光合作用(GPP)和生态系统呼吸(Re)低估约20%.

Effects of CO2 storage flux on carbon budget of forest ecosystem

Carbon dioxide (CO₂) storage flux in the air space below measurement height of eddy covariance is very important to  correctly evaluate net ecosystem exchange of CO₂ (NEE) between forest ecosystem and atmosphere. This study analyzed the dynamic variation of CO₂ storage flux and its effects on the carbon budget of a temperate broad-leaved Korean pine mixed forest at Changbai Mountains, based on the eddy covariance flux data and the vertical profile of CO₂ concentration data. The CO₂ storage flux in this forest ecosystem had typical diurnal variation, with the maximum variation appeared during the transition from stable atmospheric layer to unstable atmospheric layer. The CO₂ storage flux calculated by the change in CO₂ concentration throughout a vertical profile was not significantly different from that calculated by the change in CO₂ concentration at the measurement height of eddy covariance. The NEE of this forest ecosystem was underestimated by 25% and 19% at night and at daytime, respectively, without calculating the CO₂ storage flux at half hour scale, and was underestimated by 10% and 25% at daily scale and annual scale, respectively. Without calculating the CO₂ storage flux in this forest ecosystem, the parameters of Michaelis-Menten equation and Lloyd-Taylor equation were underestimated, and the ecosystem apparent quantum yield (α) and the ecosystem respiration rate (R_ref) at the reference temperature were mostly affected. The gross primary productivity (GPP) and ecosystem respiration (R_e) of this forest ecosystem were underestimated about 20% without calculating the CO₂ storage flux at half-hour, daily scale, and annual scale.