We partitioned the components of CO₂ flux by the chamber approaches for a 45-year-old larch forest in northern Japan. In 2003, annual soil-CO₂ efflux was averaged to 9.59 tC ha^-1, heterotrophic respiration was about 5.47 tC ha^-1 that accounted about 57% of the soil-CO₂ efflux, net annual CO₂ exchange of understory vegetation was about -0.39 tC ha^-1, annual aboveground woody tissue respiration was bout 0.75 tC ha^-1, and annual photosynthesis and respiration of the canopy was about -12.75 and 1.15 tC ha^-1, respectively. Annual GPP, NPP, NEP and ecosystem respiration for this forest was estimated to be about 13.49, 7.16, 2.04 and 11.45 tC ha^-1, respectively. The contribution of canopy respiration, aboveground woody respiration, root respiration and heterotrophic respiration to GPP was about 8.1%, 5.6%, 30.6% and 40.5%, respectively.