Host: The Japanese Forestry Society
Vertical and temporal trends in photosynthetic capacity (maximum rate of carboxylation (Vcmax) and maximum electron transport rate (Jmax)) and leaf properties (LMA and leaf nitrogen per area (Narea)) in major three species, Betula platyphylla, Quercus mongolica and Kalopanax pictus were investigated. Generally Vcmax and Jmax were lower in lower layer of their crown. Kalopanax pictus showed the highest Vcmax till August and the highest Jmax till July among species. In three species, Vcmax was maximal in late June to late July but declined slowly with increase in leaf age. Vertical variability in Vcmax was described well by changes in Narea. However, top leaves of Q. mongolica showed lower Vcmax / Narea ratio despite of higher Narea compared with lower layer (August and October), suggesting that these top leaves were suffered from some stress, such as strong light or drought. On the other hand, the relation between Vcmax and Narea differed through season and among species. Vcmax / Narea ratio was maximal in late July but declined to October in three species. In late July, the apparent fraction of leaf nitrogen to Rubisco (RF) as well as LMA reached the highest values. From these results, temporal variation in Vcmax was affected by the change in allocation of leaf nitrogen to Rubisco with leaf age. In conclusion, it was suggested that when the regression equation of Vcmax versus Narea was used for this deciduous forest, it was necessary to take account of the effects of the change in leaf age of each species.
