本研究利用微氣象與土壤含水量觀測資料，探討中部蓮華池試驗集水區常綠闊葉林之蒸發散特性。微氣象觀測資料主要用以推估潛勢蒸發散量，並選取非降雨日條件下之土壤水分損失量用以代表蒸發散量，用以分析潛勢蒸發散量之折算係數與土壤含水量變化之關係。研究發現當土壤含水量小於0.28時，折算係數隨土壤含水量增加以指數關係上升；而含水量大於0.28時，所推估之折算係數呈現較散亂分布，推測應為受植被覆蓋變化與大氣因子影響。 藉由土壤含水量變化與潛勢蒸發散量建立蒸發散折算係數可用以估算蒸發散量，與土壤水分損失所推估蒸發散量之相關係數約為0.80；而土壤水分損失與利用Eddy correlation system所觀測蒸發散量之相關係數約為0.89，未來可利用蒸發散折算係數關係式配合潛勢蒸發散量推估蒸發散量。Micrometeorological data and soil moisture variations were applied to investigate evapotranspiration (ET) characteristics of a broad-leaf forest in the Lienhuachih experimental watershed. Micrometeorological data was used to compute daily potential ET. The ET was estimated with the loss of soil moisture under the condition of non-rainfall days. The relationship between the ET coefficients and soil moisture variations was therefore obtained. The ET coefficients were exponentially increased as the increase of soil moisture when the soil moisture was less than 0.28. However the ET coefficient was scattered when the soil moisture was greater than 0.28. It is suspected that scattering pattern was affected by the land cover heterogeneity and variations of micrometeorological factors The ET coefficients obtained in this study can be used to estimate ET with potential ET and the state of soil moisture. The correlation coefficient between the loss of soil moisture and the estimated ET with ET coefficient and potential ET was 0.80. Also the correlation coefficient between the loss of soil moisture and the ET observed by the eddy correlation system was 0.89. The ET coefficient obtained is this study can be used to estimated ET with potential ET.
