The Characters And Directional Reconstruction Techniques Of Lower Water-conserving And Flood-controlling Function Of Vegetation Community In Changjiang River Three-Gorge Reservoir Basin

Our country and the world are confronted a series of vital ecological environment questions of land is degenerated and deserted, forest area is decreasing rapidly, conservatory effect and climate changes, ozonosphere destroyed, water and atmosphere pollution, ecology of city maladjustment etc. The degenerative ecosystems are in dire need of restoration and reconstruction. The phytocoenosium restoration and reconstruction in the Changjiang River Three-Gorge reservoir Basin are more pressing when the Three-Gorge engineering was built. In this study the ways of fixed experimentation and investigation, quantitative analysis and theoretic analysis combined were used. The experimental section was selected in Simianshan forestry center of Jiangjin in Chongqing. The types of phytocoenosium, the restructure and resume techniques of phytocoenosium were studied. The index system of estimating the function of flood manage of phytocoenosium in the Changjiang River Three-Gorge reservoir Basin was confirmed on the basis of the principles of system, independence, comparable, facticity and practicability. The index systems of estimating the function of flood manage of phytocoenosium in the Changjiang River Three-Gorge reservoir Basin was made in three layers: canopy layer, deadwood and litter layer and soil layer, each layer has three indexes. The index system was analyzed by Analytic Hierarchy Process, the results showed that the index system has satisfactory coherence. The method of integrative grades was used to assess the water-conserving and flood-controlling function of phytocoenosium. The index value ranges from 7.3 to 1.1. The ranges showed: Phebe chiensis forest > Cunninghamia lanceolata Hook, Pinus massoniana Lamb and broad-leaf mixed forest > Cryptomeria japonica Hooibrenk, Phebe chiensis forest > Pinus massoniana Lamb, broad-leaf mixed forest > Cunninghamia lanceolata Hook forest > Castanea mollissima Blume forest > Cryptomeria japonica Hooibrenk forest > Wasteland. The types of phytocoenosium in the Changjiang River Three-Gorge reservoir Basin belong to sub-tropic zone evergreen broad forest, they are the result from the humid season climate in sub-tropic zone. According to horizontal and vertical geographical characters of phytocoenosium of Simianshan forestry center in the Changjiang RiverThree-Gorge reservoir Basin and the amount, the effected degree of the phytocoenosium, the phytocoenosium was compartmentalized 20 types. The clustering analysis of least distance method was applied, the results showed that types of the phytocoenosium are 4: high function, commonly function, low function and degenerative function type. The result of typical correlation analysis was that the amount of litter reservesn was correlative to forest density and cover. The waterabsorption process of litter reservesn can be simulated by y = alnx + b. The relationis significant, the relative coefficients R square is above 0.85. The canopy precipitation interception is related on forest species, canopy structure, forest age and forest density, and changed due to the amount, the density, the process of precipitation, and the air temperature and wind speed. The amount of precipitation interception of several typical vegetation communities is ranges from 1.1 to 9.3 t/hm2. The difference is significant, the amount of precipitation interception of Cryptomeria japonica Hooibrenk forest is highest, the Cunninghamia lanceolata Hook, Pinus massoniana Lamb and broad-leaf mixed forest is lower. The amount of water-holding ability of different forest ranges from 1937.12-454.53t/hm2, the ranges are: Cunninghamia lanceolata Hook, Pinus massoniana Lamb and broad-leaf mixed forest > Phebe chiensis forest > Pinus massoniana Lamb and broad-leaf mixed forest > Cryptomeria japonica Hooibrenk, Phebe chiensis forest > Cunning amia lanceolata Hook forest > Cryptomeria japonica Hooibrenk forest > Wasteland. The soil infiltration process canbe simulated with f = at-b, is similar to the model of f = a1/2. The roughness rate of broad-leaf forest and broad-leaf mixed fores...