降雨截留探討的主題除了蒸發所產生的截留損失外,另一課題則爲冠層截留導致林內降雨量的再分配現象,而這個現象對地表之雨滴沖蝕可能有其重要影響。本研究選擇台灣南投縣塔塔加地區之台灣雲杉天然林分爲試驗樣區,以荷重式集雨器進行林內降雨量與林外降雨量觀測,目的爲瞭解在降雨事件發生時,雲杉林林分冠層結構對於降雨量的再分配現象。 本研究結果顯示,研究期間4 個林內觀測點的降雨累積量均小於林外累積雨量,所佔比例從72.14~94.56%不等;再根據雨場分析,台灣雲杉林的冠層飽和點最大爲6.6 mm。綜合其他相關參數採修正Rutter模式進行冠層水分平衡分析,因冠層厚度、樹冠滴落雨集水面積與遮蔽效應等因子綜合影響,截留現象造成林內降雨量有-12%~12%的再分配情形。
The main topics of rainfall interception study focus not only on interception loss by evaporation but also the rainfall redistribution caused by canopy structure and microclimate. The latter could be a main factor causing raindrop erosion inside a forest. This study aimed to view the interception phenomenon by using loadcell rainfall gauges inside and outside a natural stand of Picea morrisonicola Hay. in the Tatachia Alpine Ecosystem, central Taiwan. The results from measurements of all 4 rain gauges under canopies showed the accumulated throughfall were 72.14~94.56% of gross precipitation. The maximum interception capacity was 6.6 mm based on rainfall events analyst. A combined factor of canopy structure, drip fall water collecting area, shading effect and water flow on canopy caused a -12% to 12% rainfall redistribution according to modified Rutter model analysis.