Abstract: 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.

Key words: forest ecosystem, CO₂ storage flux, net ecosystem CO₂ exchange, Yunnan Province, flue-cured tobacco, reference crop evapotranspiration, water requirement, irrigation requirement index, climatic change.