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We report the first direct measurement of CO2 flux over Kwangneung broadleaf deciduous forest, one ofthe tower flux sites in KoFlux network. Eddy covariance system was installed on a 30 m tower along withother meteorological instruments from June to August in 2002. Although the study site was non-ideal (withvaley-like terain), turbulence characteristics from limited wind directions (i.e., 9045o) was notsignificantly different from those obtained at simple, homogeneous terains with an ideal fetch. Despitevery low rate of data retrieval, preliminary results from our analysis are encouraging and worthy offurther investigation. Ignoring the role of advection terms, the averaged net ecosystem exchange (NE) ofCO2 ranged from -1.2 to 0.7 mg m-2s-1 from June to August in 2002. The efect of weak turbulence onnocturnal NE was examined in terms of friction velocity (u*) along with the estimation of storage term.The effect of low u* on NEE was obvious with a threshold value of about 0.2 m s-1. The contribution ofstorage term to nocturnal NE was insignificant; sugesting that the CO2 stored within the forest canopyat night was probably removed by the drainage flow along the hilly terrain. This could be also an artifactof uncertainty in calculations of storage term based on a single-level concentration. The hyperbolic lightresponse curves explained >80% of variations in the observed NEE, indicating that CO2 exchange at thesite was notably light-dependent. Such a relationship can be used efectively in filing up the missing gapsin NEE data through the season. Finally, a simple scaling analysis based on a linear flow model suggestedthat advection might play a significant role in NEE evaluation at this site.