Abstract:

Diurnal and seasonal variation of CO₂ flux above the Korean Pine and broad_leaved mixed forest in Changbai Mountain were expounded according to the measurements by eddy covariance technique. The results showed that the diurnal variation during growing season was closely correlated with photosynthetically active radiation (PAR). The forest assimilated the CO₂ in daytime and released in night. The maximum uptake occurred about 9 o'clock of local time in clear day. Assimilation was synchronous to PAR in cloudy day. The night respiration increased with increasing of shallow soil temperature. The CO₂ flux also had obviously seasonal variation that was mainly controlled by temperature. Relationship between monthly net exchange of CO₂ and monthly mean air temperature fit cubic equation. Remarkable uptake occurred in blooming growing season,May to August,and weak respiration occurred in dormant season,October to March,and relatively big release happed in October. Assimilation and respiration were nearly balanced during the transition of growing and dormant seasons. The annual carbon uptake of the ecosystem was-184 gC·m^-2 .

Key words: CO₂ flux, Korean Pine and broad-leaved mixed forest, diurnal and seasonal variation