Evapotranspiration over a Japanese cypress forest. I. Eddy covariance fluxes and surface conductance characteristics for 3 years

SummaryEvapotranspiration above a Japanese cypress (Chamaecyparis obtusa Sieb. et Zucc.) forest with complex topography in central Japan were observed for 3 years using the eddy covariance method. The observations describe the magnitude and seasonal and inter-annual variations in sensible and latent heat fluxes, evapotranspiration and the parameters describing bulk canopy characteristics. Average annual evapotranspiration over the period was approximately 735 mm. Despite large fluctuations in precipitation (1179–1971 mm) during the 3 years, inter-annual fluctuations in evapotranspiration were small. Midday average dry canopy surface conductance was 6.7 mm s−1 during midseason and decreased in winter. The midday average dry canopy decoupling factor (Ω) was 0.21 during midseason and decreased in winter. This forest is characterized by relatively small values of surface conductance and decoupling factor compared to other forests. However, several other coniferous forests show smaller values. Surface conductance, and thus stomatal regulation, is important in controlling dry-canopy transpiration in this forest. Inter-annual fluctuations of bulk parameters were small; surface conductance characteristics affected by soil moisture did not vary between dry and wet years.