本研究旨在探討契約林地供混農林業使用的可行性，及其對水資源涵養的影響。研究 對象為臺大實驗林轄區内的11筆契約林地，首先，權宜方式乃參照山坡地土地可利用限度分類標 準，進行土地可利用限度分類。其次，對混農林業使用之契約林地以及近旁的造林地（對照區） 進行土壤取樣，分析土壤孔隙組成，以及進行現場的入滲試驗等，評估契約林地混農林業使用與 對照區之水資源涵養的差異。研究對象之契約林地土地可利用限度分類結果，3筆屬於宜農牧地， 其餘8筆屬於宜林地，顯示多數契約林地在坡度陡且土壤深度為甚淺層的情形下，不利於混農林業 使用。其次，土壤取樣分析結果，除了 3筆契約林地之土壤大孔隙率與粗孔隙率高於對照區之外， 其餘8筆契約林地低於對照區。而大孔隙率較高者，其小時平均入滲量及飽和水力傳導度皆較高。 另外，以土壤取樣深度0~30 cm的粗孔隙率當作計算土壤水分貯留量的基礎，結果顯示，選取的8 筆契約林地，其中有5筆的土壤水分貯留量低於對照區，差異最大者為林班地號21-322契約林地與 對照區，兩者的差值為297.6 m3/ha ,差異最小者為林班地號29-40契約林地與對照區，兩者的差值 為14.4 m3/ha。結果顯示，除了不同地點的土壤孔隙率及孔隙組成的差異之外，契約林地混農林業 使用可能減低土壤水分貯留量。

This study is to investigate the feasibility of leased forestland for agroforestry and the influence on water conservation. Eleven leased forestlands within NTU Experimental Forest were selected. Firstly, land use capability classification was examined expediently according to the Slopeland Conservation and Utilization Regulations Implementing Rules. Secondly, in the leased forestlands and nearby plantations (as control areas), soil sampling and field infiltration test were conducted to analyzesoil porosity structure and evaluate the differences of water conservation between leased forestlands and control areas. The land use capability classification result showed that three leased forestlands could be agricultural and/or pastoral land usage and the rest eight leased forestlands were suggested to afforestation. This finding indicated that most of leased forestlands are not favorable for agroforestry due to steep slope and shallow soil depth. Secondly, the analysis of soil samples showed that the soil macroporosity and coarse porosity rates of eight leased forestlands were less than their control areas. Additionally, the higher macroporosity rate showed higher averaged hourly infiltration capacity and saturated hydraulic conductivity. Besides, water storage capacity was calculated according to the soil coarse porosity of sampling depth 0-30 cm. The result showed that soil water storage capacity of five agroforestry leased forestlands were less than control areas. The highest gap of water storage capacity lies in the leased forestland No. 21-322 and its control area with 297.6 m3/ha difference. The smallest gap of water storage capacity lies in the leased forestland No. 29-40 and its control area with 14.4 m3/ha difference. The result further revealed that agroforestry leased forestland possibly reduce the water storage capacity.