Canopy conductance and gas exchange of a Japanese cypress forest after rainfall‐induced wetness

Abstract

AbstractIncreased stomatal conductance of the dry leaves right after wetness ended was reported before, while few studies paid attention to this phenomenon in canopy scale and its contribution to the forest carbon sink function. Therefore, we observed the continuous change of canopy wetness and ecosystem fluxes after wetness ended by using wetness sensors and eddy covariance method for a Japanese cypress forest (Chamaecyparis obtuse Sieb. Et Zucc.) in the Asian monsoon area. Larger gc (canopy conductance) were found in the relationships with both vapor pressure deficit and Rn (net radiation) during the first several hours after wetness ended. The results for λE (latent heat flux) were similar to that of gc in spring and summer. Net ecosystem exchange (NEE) in the relationships with Rn at different stages after wetness ended did not show clear difference except in spring. Nevertheless, annual summed‐up NEE showed that the average CO2 uptake at the first several hours after wetness ended was larger than the usual dry period. These results suggest that the improved stomatal opening at the first several hours after wetness ended plays a significant role in the canopy‐scale gas exchange processes.