Abstract
Numerous studies have been performed to examine forest evapotranspiration based on flux measurements since 1990s. However, no paper has clarified what was obtained by these studies. This paper answered the question. The authors assumed that the ultimate purpose of forest evapotranspiration research was to predict evapotranspiration rates from any forests. For this purpose, we firstly need to formulate evapotranspiration rates as functions of meteorological factors and model parameters, and secondarily need to relate the model parameters to forest properties (e. g., broad-leaved/coniferous, leaf area index, canopy height, etc.). The first step had been already accomplished before 1990s. The second step became possible by the presence of the studies with flux measurements, because the second step required accumulation of evapotranspiration data from various forests with different properties.
