The Study On Niche Characteristics Of Understory Vegetation Under Different Plantation Community In Alpine Region Of Qinghai

Datong county of Qinghai is located in alpine areas, is the transition zone between Qilian Mountains and the Loess Plateau.This article applies the ecology theory and method, from the views of biodiversity, niche breadth, niche overlapping, niche similar proportion and ecological response, using the quadrat data of the field survey and the local data from Baoku forest, conducting research on the ecological characteristics of understory vegetation of major plantation community, making the following conclusions:The species diversity of herbaceous layer and shrub layer of different plantation community are measured by species richness index, shannon-Wiener index, Simpson index, Pielou index.It shows that broadleaf plantations is more conducive to the recovery and development of the species diversity of shrub layer, coniferous plantation is more conducive to the recovery and development of the species diversity of herbaceous layer.In order to show growth of herb community niche of different plantation communities from niche breadt’ view.the niche breadth of herb community and shrub community are measured by means of levins niche breadth in different plantation communities.It shows that wide ecological amplitude of species is different in different plantation communities, Pure plantation is the best for the development and regeneration of understory shrub communities. Mixed plantation is the best for the development and regeneration of understory shrub communities.The niche overlap of herb community and shrub community are measured by means of pianka niche overlapping indexes in different plantation communities. The niche overlap index suggest that the species with big niche breadth often have big niche overlapping. But in some plantation communities, the species with narrow niche breadth have big niche overlapping, This phenomenon may be due to different shrub community and herb community competition with each other for limited environmental resources, and shrub community of pure plantation have the more intense competition than shrub community of mixed plantation, and herb community of mixed plantation have the more intense competition than herb community of prue plantation.According to the results of niche similarity in shrub layer and herbal layer.lt shows that Species with wide niche breadth had high niche similarity proportion.The main population of pure understory shrub layer with wide niche breadth also had high niche similarity proportion, The main population of herbaceous layer under mixed forest with wide niche breadth also had high niche similarity proportion.From the eco corresponding, the niche width larger populations of different plantation community is mostly in the development stage,the niche width smaller populations of different plantation community is mostly in the failing stage. From the eco-response rate,the shrub layer and herbaceous layer’s populations of different plantation communities are in the constantly changing process, New species will be developed for the dominant species in the future development.