Study on the Variation of Soil Clay Minerals and Influence Factors in Karst Regions under Different Rocky Desertification, Southwest China
|School||Nanjing Agricultural College|
|Keywords||karst region rock desertification clay minerals influencing factors|
Rocky desertification seriously restrictes economic and social development in karst regions of southwest China. The essence of rocky desertification is the decline of soil quality. As the main component, soil minerals which account for 95%～98% of the quality of solid phrase form the skeleton of soil. There are many kinds of soil minerals, approximately 3300 kinds. The composition, structure and property of soil minerals have effects on soil physical and chemical properties, the keeping and releasing of soil nutrient and soil forming process. Thus, the study on composition and content of clay minerals of soil under rocky desertification has important significance to rational utilization of land and improvement of ecological environment.As the typical region under rock desertification, Libo and Puding counties in Guizhou province were chose for study area. By taking the soil under different periods of rock desertification as the research object, the composition and its variation status of clay minerals, the composition of silt and sand minerals, and the dependence factors of mass fraction of clay minerals in different layers of different soil profiles were analyzed in research area, providing scientific data for ecological restoration in soil degradation process in karst region.The following conclusions can be formed from this work.(1) The variation of soil clay minerals was studied, and the results were as follows:①The compositions of clay minerals from each rocky desertification were the same. They were kaolinite, montmorillonite and illite etc.②From Non-degraded stage and Light rocky desertification to Moderate rocky desertification, the content of montmorillonite in surface soil layer increased gradually, was 27.82%,29.34% and 58.32% respectively. The content of kaolinite in surface soil layer also increased gradually, which was:21.39%,31.81% and 36.93% respectively. But the content of illite in surface soil layer reduced gradually, which was:50.79%,38.85% and 4.75% respectively.③The pedogenesis and environment of soil in Karst Regions were similar, so the composition of clay minerals also were the same. Therefore the difference content of clay minerals showed the difference in degree and phase of the pedogenesis.④There was a high degree of correlation among the concentration of kaolinite, montmorillonite and illite in Karst Regions. The correlation coefficient was 0.9703 and 0.9456 respectively, both reaching the significant level.⑤The primary clay minerals in particle mineral were quartz,feldspar and muscovite, and the primary clay minerals in sandy mineral is quartz,feldspar and muscovite.(2) The correlation study of soil physical properties and clay minerals showed:①there was a extremely significant linear positive correlation between soil porosity and the content of montmorillonite. The regression equation was y= 0.6751x-8.1324, with a relative coefficient 0.8002.②There was a extremely significant linear positive correlation between soil porosity and the content of kaolinite. The regression equation was y= 0.4348x +0.8466, with a relative coefficient 0.8972.③there was a extremely significant linear negative correlation between soil porosity and the content of illite, and the regression equation was y=-1.1099x+107.29, with a relative coefficient 0.9143.