The Analysis About Change Of Structure Of Plant Community And Stoichiometry In Different Succession Stage In Eastern Qinghai-Tibet Plateau

The study is based on the five different succession stages in the alpine meadow, analyzing the species composition, vegetation coverage、importance value、species diversity and other ecological index even the stoichiometric characteristics of nitrogen and phosphorus of soil and the dominant species of plants in the community in the process of vegetation succession. Indicating the change rule of species diversity, dominant species and soil nutrient even the relationship of stoichiometric characteristics between them in the process of vegetation succession in the alpine meadow.There is no significant difference between the community vegetation coverage of five succession stages,that is to say, with the process of succession,there is no obviously fluctuant trend. It has wide community vegetation coverage in the process of vegetation succession. The species diversity is a descending trend from A phase to B phase, so is the community productivity. However, the species diversity continues to increase from the beginning of the B stage of the succession process and community productivity starts ascending from the beginning of the C stage. Species diversity is in the middle level when community productivity reach maximum. Species diversity reached a maximum in succession later, species abundance increased with succession of normal.A stage(the early stage of succession) has become the functional group that weed plants are dominant species because of the reproduction and growth of the invasive species Cephanoplos and the dominant species including Herba erodll and Artemisia tangutica. In the B stage, Elymus dahuricus and Medicago sativa has become dominant species. Elymus began to degenerate and Leguminous plants appeared and became the dominant species in the C stage. Asteraceae weeds invasion resulted in serious degradation of Elymus nutans in the D stage. E stage is the shrub community that Potentilla fruticosa is the dominant species. Artemisia tangutica and Potentilla anserina species are also dominant species. The study indicates the ecosystem function index of shrub community tends to be stable, closing to the climax succession at the moment.The relationship between Soil available nitrogen and N content in plant leaves appears obvious positive correlation(p<0.05). However there is no significant correlation was observed between the middle and bottom soil nitrogen and soil available N content in plant leaves(p>0.05).The relationship between soil total N,P content and N,P content in plant leaves is obvious positive correlation, but middle soil total N,P content and N,P content in plant leaves lacks significant relativity. It shows that the nutrient content of leaves is mainly controlled by soil nutrient content, rather than middle and bottom soil nutrient content. Five stages of succession, soil and plant N: P change is synchronous, dominant species of leaf N: P values between 7.97 and 11.92, the arithmetic mean is 9.258, less than 14. So the growth of the subalpine meadow plants under nitrogen limitation.