Research On Hydrological Function Mechanism And Spatial Scenarios Of Forest In Three Gorges Reservior Area

The research on the hydroglogical function mechanism and spatial scenarios of forest in Three Gorges Reservior Area was conducted, which are associated with the national tenth-five year plan of state key task of scientific and technological research "Technology Research and Demonstration of Vegetation Construction with Water Conservation Function in Three Gorges Reservoir Area, Yangtse Basin " (2001BA510-02). The purpose of this paper is to provide evidence for vegetation construction with hydrological function in Three Gorges Reservoir Area and even in Yangtse Basin.On slope scale, hydrological function mechanism of typical forest communities were investigated and evaluated based on the quantitative analysis in hydrological effects of canopy, litters and soil layers and slope runoff characteristics in the 11^th rainstorm conditions by the methods of modeling, statistical method, elasticity analysis, marginal yield analysis, grey correlation analysis, PCA (principal component analysis), FCA (fuzzy-clustering analysis), fractal theory and so on. The canopy capacity takes on down trend with the increasing of rainstorm, and the maxium rate occurred in the about 60 mm of precipitation.The best hydrolgogical function of litters is mainly observed within the first 2 hours of precipitaiton, especially in the first 30 minutes. The forest soil had the ability of regulating the maximum diurnal rainfall; in the initial phase [0,5min]of infiltration, the structure of A soil genetic horizon is the major influencing factor; in transition phase (5,30min]of infiltration, the pore distribution of AB horizon and soil structure of B horizon are the major influencing factors; in the stable phase (30,180min]of infiltration, the soil structure of C horizon is the major factor affecting the infiltration velocity.The optimal index to represent the soil anti-erodibility is conglobation degree of soil. The anti-scour coefficient is closely related to the thickness of soil horizon. The internal friction angle is significantly affected by both the particle size distribution and aggregate size distribution; however, the cohesion is mainly influenced by particle size distribution. Under the condition of rainstorms, there is significant positive linear correlation between slope surface runoff and storm rainfall, slope surface runoff duration and rainfall duration. The responses of surface runoff peak and groundwater flow peak were weak on rainstorm peak. The optimal hydrological function of soil layer led to inapparent response of groundwater flow on rainstorm.Then, the method of Analytic Hierarchy Process (AHP) was applied to establish the hydrological hierarchy function model of forest communities, and integrative grades were used to give static evaluation, the results of static evaluation showed that: evergreen broadleaf shrub forest> evergreen...