Carbon uptake by the oceans and by the terrestrial biosphere can be partitioned using changes in the ¹²C/¹³C isotopic ratio (d¹³C) of atmospheric carbon dioxide, because terrestrial photosynthesis strongly discriminates against ¹³CO₂, whereas ocean uptake does not. This approach depends on accurate estimates of the carbon isotopic discrimination of terrestrial photosynthesis at large regional scales, yet terrestrial ecosystem heterogeneity makes such estimates problematic. Thus, accurate estimate of D is important to evaluate the magnitude and spatial distribution of terrestrial uptake of carbon dioxide. Recent study showed that ablated plant wax compounds in continental air masses can be used to estimate D over large spatial scales and at less than monthly temporal resolution¹. However, the temporal and seasonal patterns of direct D in the forest ecosystem estimated by plant-derived biomarkers have been little known because of its subject to considerable uncertainty. In this study, we measured ¹³C and ¹⁴C isotopic compositions of plant-derived biomarkers (n-Fatty acids and n-Alkanes) in forest aerosols and plant material in order to evaluate direct mean D values at the ecosystem-level and plant biosynthetic fractionation.