Study On The Vegetation Community Diversities And The Partition Of Degradation Phases Of Degraded Hill Of Xiaolangdi Reservoir Area

Xiaolangdi project on Yellow river is the second important water conservancy that crossing century which is only inferior to the Three-Gorge engineering in China. The project is the pivotal engineering about controlling and exploiting Yellow river, which belongs to the vital item of the eighth five-year plan of our country. The aim of the project is mainly to prevent or control flood, decrease sullage, then water supply, irrigation, generating electricity, cumulating clear water and letting muddy water, eliminating calamity and bringing benefits, utilizing synthetically are the part-time goal of the project. This paper analyzed the community diversities of vegetation on the mountanious region and plotted out different degradation phases of the upland ecosystem that surrounding Xiaolangdi reservoir area by means of setting 51 plot samples including seventeen 10×10m2 plot samples for arbor woods and thirty-four 2×2 m2 ones for shrubbery and tussock. At last, some advice were bring forward for resuming the healthy ecosystem of the research area.1,Using all plot samples as analyzing objects and the investigated information of arbor woods, shrubbery and tussock as basal data, The Shannon-Wiener index(H'), Simpson index (D1), interspecies encounter odds (PIE), Pielou evenness index(Jsw and Jsi), Patrick species richness index(D2)and Margalef species richness index(D3)were used to study the community diversities of vegetation of Xiaolangdi reservoir area and the variety rule of the community diversities along with environment facters such as altitude, slope aspect and so on. The results are as follows:(1)According to the measuring results, the upper seven indexes appeared consistent changing rules. (2)As a whole, the community diversities of different layers in 51 plot samples had a variety law that the herb layer has the highest values of diversity index, shrub layer the second, and tree layer the least.(3)Along with the rising of altitude, the species richness index and diversity index of shrub layer and herb layer descended gradually.(4)Because of the difference of light, heat and water conditions between south and north slope, the north slope has the more flourishing vegetation, more complicated community structure and species buildup and higher values of species richness index and diversity index than the south slope.(5)the community diversities of vegetation of Xiaolangdi reservoir area were influenced by nature environment conditions and people's activities, among which the atrocious local nature environment conditions were the primary reason for the severe degradation of vegetation of Xiaolangdi reservoir area.2,Through major component and cluster analysis on computer, diversity index and altitude, gradient, slope aspect, soil types, soil thickness, gradient content, water-soil loss degree were used to study and plot out different degradation phases of the upland ecosystem of Xiaolangdi reservoir area. The results are as follows:The four major components contained two kinds of effect facters that were diversity index and nature environment conditions. According to the local nature environment conditions and vegetation situations, upland ecosystem of Xiaolangdi reservoir area should be plotted into four different degradation phases: the initial stage of degradation with a few trees, evolving stage with tall shrub, serious stage with herbage and extreme stage with no vegetation. There were distinct difference in community structure and environment characteristic among each degradation phases.According to the environment and biologic characters, some measures were bring forward to restore and rebuild local healthy ecosystem.