Relationship between forest stand density, leaf surface area, and amount of photosynthesis and transpiration in the coastal black pine forest of Northern Kyushu

The leaf surface area, biomass of leaves, and amount of photosynthesis and transpiration of trees for the unit forest area were measured over the course of a year in the coastal black pine forests of various stand densities in Northern Kyushu. The hydraulic resistance, i.e., the ratio of water potential to transpiration rate, at the top and middle of long branches was also measured in summer, when the rate was high. As a result, as the forest stand density became lower, the leaf surface area, biomass of leaves, and photosynthesis amount increased. The amount of transpiration amount positively correlated with the amount of photosynthesis. There was no difference in hydraulic resistance between the top and middle of the branches, demonstrating that the ability of growth was maintained even at the ends of the branches. Here, further branch growth could be expected. With the lowering of the forest stand density by thinning the number of trees, forest stand growth will be promoted by the action of photosynthesis and the expected growth of branches.