蒸發散不僅在水平衡收支裡扮演重要的角色，同時對陸氣交互作用之地表過程也有重大之影響。利用渦流相關系統觀測地表通量，以及所收集的微氣象變數，計算出空氣動力導度、植被導度與退耦係數，並以樹液探針量測樹液流速。本研究目的為：(1)利用退耦係數的概念，了解乾濕季內蒸發散的驅動營力，並探討植被層與大氣間耦合的情形。(2)以樹液探針量測現地的樹液流變動情形，觀察流速變化與環境變數的相關性。研究成果指出，乾濕季平均退耦係數分別為0.20與0.34，平均植被導度分別為0.0047 m/s和0.0075 m/s，平均空氣動力導度皆為0.06 m/s。乾季時的樹液流動較為規律，具有日循環特徵，且淨輻射量與飽和蒸氣壓差對蒸散作用的影響較為顯著。降雨時期的樹液流資料較為散亂，呈現的變化曲線較為不平整。Evapotranspiration (ET) not only plays an important role of water budget, but also significantly affects surface hydrology processes. Surface fluxes were observed with an eddy covariance system in association with environmental factors measurements for computing aerodynamic conductance, canopy conductance and decoupling coefficient. Moreover, sap flow was measured by sap flow probes designed in this study.The purpose of this study included: (1) to investigate seasonal characteristics of evapotranspiration in association with the decoupling coefficients for examining interactions between canopy and atmosphere. (2) to study the correlation between sap flow velocities and environmental variables by sap flow probes designed in this study.For dry and wet seasons, the decoupling coefficients of 0.20 and 0.34, respectively, the canopy conductance were 0.0047 m/s and 0.0075 m/s, respectively; the aerodynamic conductances were equally 0.06 m/s. During dry season, sap flow data shows significant diurnal cycles; radiation and vapor pressure deficit are concluded as major driving factors of tree transpiration. However, the wet season sap flow data presents irregular patterns due to frequent rainfalls.
