Abstract
To understand the magnitude of changes in evapotranspiration and the main controlling factors of such changes, in association with the long-term natural recovery of forests on denuded hills, we compared the mean annual evapotranspiration during the early 10-year period (initial stage of forest recovery) and late 10-year period (60 years after the early period; transition stage of forest recovery) as measured by the water balance method. The Ananomiya experimental watershed at the Ecohydrology Research Institute (The University of Tokyo Forests) was selected for this study. The 10-year mean annual loss, as calculated by the annual water balance for the late period was 89 mm larger than that measured for the early period. We propose a new method, based on the short term water balance method, to estimate of annual evapotranspiration and have applied this method to evaluate the relationship between annual evapotranspiration and mean annual temperature, annual precipitation, and annual number of days with precipitation. The mean annual evapotranspiration for the late period was 80 mm larger than that measured for the early period. We conclude that the main reason for higher evapotranspiration in the late period may have been the increase in canopy interception as a consequence of forest growth.
