| Firstly, the weighted average of saturation water-holding capacity of forest soil and maximum rainfall (one day) during the 40 years were used to determine the suitable forest coverage of Pingtong River catchments, the typical watershed in the middle and upper reaches of the Yangtze River. Secondly, through application of interpreted ETM+ in 2006, 1：50000 forest map, topographical map, data of Class II forest survey in 2007, the stand structure, production capacity and ecological function were selected to evaluate the grade of each grid by using matter element model. Thirdly, the AHP was applied to modify the spatial structure and form the spatial location allocation of protection forest systems.The results showed that: (1) The suitable forest coverage was 57.09%; (2) On the whole, the quality of protection forest was bad; of which, the middle grade occupied 67.29%, bad grade of 17.15% and good grade of 0.78%;(3) After optimization, the ranking by proportion of forest category was as follow: water and soil conservation forest (44.31%)> firewood forest (18.00%)> water conservation forest (17.97%)> general timber forest(8.12%)>woody medicinal forest(5.25%)> industrial raw material forest (4.00%)> fruit tree forest(1.75%)> industrial economy(0.60%); (4) On the base of landform and site condition, the tree species that had a good function of soil and water conservation should be selected, and mixed forests with proper canopy density consisting of coniferous and broadleaf species should be established with trees, shrubs and grasses. Furthermore, a certainly amount of the tree species that had economic value should be selected so that both the regional economic benefit and farmers income could increased; (5)After achievement of the optimal spatial allocation, 163 million yuan economicvalue, the increase of 2 158.76 伊104 m3 of water conservation, reduction of sediment of 6.8×10^4 t could be achieved. |
