| Rocky mountain area of north China is a key area of ecological construction in China, which has fragile ecological environment, serious soil and water erosion, increasing desertification, frequent natural disasters. But, the spatial layout and structural configuration of protective forest is unreasonable, which seriously prevented the play of the ecological function of protective forest. In order to optimize the space allocation of protective forest, this study combine with"study on space allocation and structure optimization technology of protective forest system"which supported by"Eleventh Five-Year"National Science and Technology, at a scale of basin, from the relation of appropriate forest coverage, proportions of forest types, space allocation and water conservation function, deeply studied the space allocation of protective forest and the relation of protective forest system and water and soil resources in Hongmenchuan Basin of rocky mountain area of north China, proposed the model of the space allocation of protective forest of typical basin.This paper is based on the hydrometeorological data of Hongmenchuan Basin in the years of 1990-2006, by using remote sensing data of four periods studied landscape features of land use of the basin in different periods.From the angel of landscape patche feature index, landscape heterogeneity index, landscape diversity index and transfer matrix of landscape types, deeply analyzed evolution characteristics of land use pattern of the basin; by using principal component analysis method, analyzed the driving factors of the landscape type change of the basin, determined and analyzed the main driving force of the land use change of the basin; then, analyzed the change law of precipitation and runoff of the basin, and studied the water conservation function of protective forest combined with the change of land use/forest vegetation.On the basis of parameter calibration, identified the applicability of SWAT model in Hongmenchuan Basin, and simulate the runoff response of collaborative change of precipitation and forest vegetation by using the model. From the sides of forest coverage ratio, propotions of forest type and space allocation, set different scenarios and simulated runoff yield of normal year, obtained the optimization program of space allocation of protective forest of the basin. The main research results are as follows:(1)During the years of 1990～2005, although forest types of Hongmenchuan Basin changed a lot, dominated by coniferous forest and broad-leaved forest. Landscape has a visible fragmentation trend, and the plaques showed a irregular trend. Sphere of influence and intensity of human factors on land use increased in the process of accelerated economic development.(2)During the years of 1990～2006, although precipitation and runoff of Hongmenchuan Basin fluctuated, showed a downward trend totally, the rate of the decrease of runoff was much larger than the rate of the decrease of precipitation. Runoff has a visible stage, the runoff in the years of 1990～1998 was larger, but the runoff in the later period was relatively small, for the land use which has a good vegetation condition, the ability of runoff yield of the later period decreased compared with the previous.(3)By the use of sensitivity analysis and automatic model calibration, studied the applicability of SWAT model in the basin, obtained a better verification. On the basis of it, simulated and obtained the collaborative response of the change of precipitation and forest vegetation, and the impact of forest vegetation change on the runoff yield of flood season and wet year was larger was discovered.The function of storing runoff of different forest types were different, the order is: shrubbery < coniferous forest < mixed forest < broad-leaved forest.(4)Five factors of landscape, slope, aspect, soil thickness and soil parent material were selected, divided site condition of Hongmenchuan Basin, 17 kinds of site conditions were obtained. Based on forest coverage ratio, 7 kinds of scenarios were set, according to site condition, carried out the space allocation of protective forest. Simulate runoff yield of different space allocations of protective forest by using SWAT model, the results showed that: when the forest coverage ratio is 70%, the runoff yield of the basin is smaller than the measured in the year of 2004, the protective forest showed a better water conservation function, and could be considered retional forest coverage ratio. And under the condition of the propotions of forest types——31.58% for broad-leaved forest, 22.96% for coniferous forest, 35.53% for mixed forest, 9.93% for shrubbery, the function of storing runoff of protective forest showed the best. At present, the forest coverage ratio of the study area has been achieved 76%, which can fully able to meet the local ecological requirements, there is no need to increase the area of protective forest. But, the internal structure is not reasonable, the objective should be converted to adjust forest structure in the future.
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