Canopy conductance for a Moso bamboo (Phyllostachys pubescens) forest in western Japan

Abstract

In western Japan, Moso bamboo (Phyllostachys pubescens) forests have been expanding by replacing surrounding forests (e.g., coniferous plantation forests), which raises concerns about possible changes in terrestrial water and carbon cycles. Canopy conductance (Gc) is a critical parameter for determining canopy transpiration and photosynthesis. To clarify the characteristics of Gc for Moso bamboo forests, we calculated Gc during a growing season for a Moso bamboo forest on the basis of canopy transpiration measurements made using the sap-flux method, and then compared the Gc value with values for coniferous plantation forests in western Japan. Gc was primarily related to the vapor pressure deficit and secondarily to solar radiation, similar to the results obtained for other temperate forests. Under light-saturated conditions, Gc for the bamboo forest was approximately twice that for the coniferous plantation forests despite the lower leaf area index for the bamboo forest. This implies higher canopy transpiration and photosynthesis for the bamboo forest, and therefore possible changes in terrestrial water and carbon cycles due to the replacement of coniferous plantation forests by bamboo forests.