Quantifying transpiration in a coniferous forest: Assessment of the summed components methods, sap-flow, and stable isotope techniques

Vegetable transpiration is one of the most important processes in the soil-plant-atmosphere-continuum (SPAC) water cycle. The objectives of this study were to (1) evaluate the efficiency of the different research methods, (2) investigate and quantify evapotranspiration and its components in an alpine watershed from April to October 2009. We investigated evapotranspiration and its components in the Gongga Mountains, which are located on the southeastern fringe of the Qinghai-Tibet Plateau, using summed components methods, sap-flow, and stable isotope techniques. The annual evapotranspiration calculated by summed components methods was 747 mm accounted for 50% of the total water input. In which, soil evaporation was account for 6% of the total evapotranspiration. The vegetation transpiration calculated by sap-flow techniques accounted for 19% of total evapotranspiration. The intercepted rainfall evaporation accounted for 75% of total evapotranspiration.