Japanese beech (Fagus crenata) and oak (Quercus cripsula) are the major species in the temperate forests in central to northern Japan. Although the growth of these species are though free from water stresses due to the cool and less evaporative environments, recent studies showed higher vulnerability to drought-induced cavitation in species from wet and less-evaporative environments, like Japanese beech oak. This study investigated the influences on the gas exchange by factors that are not included in a simple model simulation (leaf photosynthetic traits and microenvironments of the canopy), through continuous monitoring of sap flux. Sap fluxes (Fd) were monitored using heat ration method sap flux sensors at different depths and were converted to stomatal conductance per sapwood (Gs). A simple multilayered gas exchange model computed these parameters (Fd_m and Gs_m), taking into consideration the microclimate at leaf surface, energy balance and physiological reactions as the function of the leaf ecophysiological traits and the microenvironments. This presentation discuss about the potential effects of lowered Gs from early morning on the annual cumulative gas exchange (Gs and Fd) of these species in each site.