Study on Soil Physical and Chemical Properties in the Process of Vegetation Succession in Karst Area of Eastern Yunnan

The process of natural succession of restoring vegetation in eastern Yuannan after rocky desertification in Karst area appearing was divided into the herbosa stage,the stage of herbosa-shrub,the shrub stage,the stage of subaltern tree forest,the stage of Lithocarpus dealbatus-Quercus aquifolioies forest,the stage of Sawtooth oak-Quercus aquifolioies forest and the stage of Quercus aquifolioies forest.The physical and chemical properties of soil were studied by using space insteading of time.The results showed that,in the process of vegetation succession in Karst area in eastern Yunnan,the bulk density of soil decreased gradually from the stage of herbosa-shrub,and the least value appeared in the stage of Sawtooth oak-Quercus aquifolioies forest,then the bulk density of soil rose in the stage of Quercus aquifolioies forest.But the soil porosity was contrary to the bulk density of soil.The soil was weak acid in the whole proless of succession.The content of OM,virtual nutritions and total N rose from the stage of herbosa-shrub and reached the most value in the stage of Quercus aquifolioies forest.The content of total P rose firstly,then decreased,rosed finally and the two peaks of wave appeared in the stage of Lithocarpus dealbatus-Quercus aquifolioies forest and the stage of Quercus aquifolioies forest.The content of total K rosed gradually and reached the most in the stage of Lithocarpus dealbatus-Quercus aquifolioies forest,then decreased.