Study on optimum forest coverage for water conservation: a case study in Pingtonghe watershed (Pingwu section) Zhu Zhifang Gong Gutang Chen Junhua Mu Changlong (Institute of Forest Ecology and Resource Environment, Sichuan Academy of Forestry, Chengdu 610081, Sichuan) Abstract: Appropriate forest coverage is the basis of spatial layout for watershed protection forest and is an important indicator for regulating sheltering forest and stand restructuring in watershed. In this paper soil saturated water holding capacity (SWC) was selected as the indicator for assessing water conservation function at watershed scale. analytic hierarchy process (AHP) method was applied to eliminate indicators with close relevance. 12 indicators related to landform (position on slope and slope gradient),-soil (soil types and soil depth), forest (structure, standing volume, crown cover and stand age) and disturbance regimes (forest types, distance from villages, elevation and annual per capita income) were used to estimate soil saturated water holding capacity were selected for the assessment. The AHP method was applied to calculate each indicator’s weight to SWC, based on which water conservation class of each forested sub-compartment were calculated. The maximal daily rainfall of 147.2mm in last 40years was thenused to predict the optimum watershed forest coverage. The result indicated that the most important factor for assessing water conservation is forest factors (0.637), followed by disturbance factors(0.258) andlandform-soil factors (0.105) The optimum forest coverage in the assessed watershed is 57.09%, with ranging from 43%～73% . Kew words: water conservation; indicators; forested subcompartment; soil saturated water content (SWC); optimum forest coverage