The Central Of Yunnan Plateau Ecological Stoichiometry Characteristics Of The Typical Vegetation Succession Process

This thesis researches the stages of succession of the typical vegetation in Yunnan Plateau on plant leaves, roots, soil, litter, the element content of C, N, P, K, Ca, Mg, Na and the stoichiometric ratio characteristics, the relationship between the research objects and the elements and the impact factors of the stoichiometric ratio, aiming at estimating the nutrient limit condition of the typical vegetation and revealing the synergistic trend among the plant characteristics during the process of typical vegetation succession in the small-scale level. The results showed that as follows:(1) The content of the leaf C and Mg showing first increases then decreases vary with the process of vegetation succession, while P, K content decreases, and N, Ca and Na content fluctuates; N, P, K, Ca and Mg content among the leaves shows obvious linear relationship, elements of plant leaves are impacted by the N, P, K and Na content in their roots greatly; the ratio of C/N, N/P, Mg/Na in the plant leaves appears fluctuation with the vegetation succession processed, the ratio of K/Ca, Ca/Mg shows downtrend with it, and the ratio of P/K first increases then decreases; at the initial phase of vegetation succession, the grass and shrub community growth are restrained by the content of N, P. At the medium time, the mixed forest community growth is restrained by the content of N, K. at the later stage, the broad-leaved forest community development is restrained by the content of P, K; with the change of vegetation type, the impact factors of the elements stoichiometric ratio in plant leaves are different; the stoichiometric ratios relates to each other.(2) the content of C, N, P, Ca, Na in plant coarse roots rises with the process of vegetation succession, and the content of K, Mg decreases; the content of N, P, Ca, Mg in plant fine roots rises with the process of vegetation succession, and the content of C, K, Na declines; the content of N, P, K in the root system itself has greater impact on the content of other elements; the correlation between coarse roots and fine roots elements differs; the content of P, K, Mg in the soil has great impact on the roots element; the content of C/N, P/K and Mg/Na of plant roots than first increases then decreases, the ratio of N/P, K/Ca first decreases then increases, the ratio of Ca/Mg fluctuates; the elements in the soil has a little influence on the root elements stoichiometric ratio, and it is jointly regulated by its own various elements.(3) The soil bulk density decreases with the vegetation succession process and increased with the soil depth; the soil porosity increases with the vegetation succession process and decreases with the soil depth; the content of C, N, Na in the soil first increases and decreases with the vegetation succession process, the content of K, Ca, Mg appears downtrend with the succession process in general, and the content of P fluctuates; on the vertical profile, the content of C in the soil under four different vegetation decreases with soil depth, while the content of N changes with no apparent rule, the content of P, K distributes uniformly in the vertical profile, the content of Ca, Mg, Na first increases then decreases with soil depth; the content of C, P, K, Ca, Mg in the soil shows obvious linear relationship; a considerable part of K, Mg element comes from the return of litter; all stoichiometric ratios in the soil first increase then decrease; under the different vegetation, the ratio of C/N decreases with soil depth, the ratio of P/K, Ca/Mg, Mg/Na first increase and then decrease with soil depth, while the ratio of N/P, K/Ca increases; the stoichiometric ratio of soil elements of grass, shrub conifer forest commonly controlled by of the content of C, P, K, Ca, Mg, Na in the soil, and the stoichiometric ratio of the soil elements in the broad-leaved forest is subject to the content of C, N, P, K, Ca, Mg.(4) as for litter reserves of four kinds of vegetation, the mixed coniferous forest has the most, broad-leaved forest takes second place, and the grass follows; in the litter, the content of C, K, Ca, Mg reduces with the succession process, the content of N first increases then decreases, the content of P and Na fluctuates in the succession process; the content of C, K, Ca, Mg, Na in the litter has significant correlation; the ratio of C/N, Ca/Mg in the litter first decreases then increases, the ratio of N/P, K/Ca is otherwise, the ratio of P/K increases, and the ratio of Mg/Na reduces; the litter stoichiometry ratio has a significant linear relationship with its elements.