The Biogeochemical Characters Of Element In Limestone Soil In Guilin, Guangxi

Abstract: Taking an example of limestone soil and red soil. The limestone soil and red soil are located in Maocun, Guilin. Comparing the pH value, the contents of tatal element(C,N,P,K,Na,Ca,Mg,Fe,Mn,Cu,Zn,Mo,B,Se,Sr,I,V,Co,Ni,Cr,As,Cd,Pb) and available contents of mineral elements, organic compounds and chemical compositions of plants , the coefficients of biological absorption of elements and the relationships among elements of limestone soil to red soil. The chiefly results were as follows: 1. The contents of elements in limestone soil were higher than that in red soil beside K,Na,B, Mo and I. As to the contents of elements in plants, it was found that the plants living in limestone soil had higher contents of elements than the plants living in red soil, but the content of K in plant living in limestone soil was lower than that in the red soil. The pH value of limestone soil was higher than the pH value of red soil .The total content and available content of Ca in limestone soil profile were twenty to a hundred times higher than that in the red soil profile. It was found that the total content of Ca in limestone soil was three times higher than that in the red soil. The pH value of limestone soil profile was neutral and tend to alkalinity .So the character of limestone was abundant in Ca and the pH value was higher. 2. Correlation analysis indicated that relationships between the pH value,the total content of Ca and the available contents of trace elements in limestone rhizospheric soil were maily negative. However the relationships in the red rhizospheric soil were maily positive .The ratio of available/total content of Ca was negatively related to the ratio available/total contents of trace elements in limestone soil profile, and the correlations were significant. The correlations of red soil profile were opposite to the limestone soil profile. 3. Relationships between organic compounds and available contents were maily positive in rhizospheric soil of trace elements, especially in the limestone rhizospheric soil. The available contents of trace elements had positive relativity with organic compounds beside Mo and Se.The same to the available contents of trace elements and the ratio of available/total contents of trace elements in soil profile. 4.Correlations among different contents of available trace elements and different ratio of available/total content of trace elements were chiely positive in rhizospheric soil and soil profile. There were more significant correlations in limestone rhizospheric soil than in the red soil. Correlations of soil profile were reverse to the rhizospheric soil. 5. Relationships between available content of Sr and other elements were maily negative .On the other hand, relationships between available content of Fe, Co and that of other elements were chiefly positive. Relationship between the availa ble/total content ratio of Ca, Co and the ratio of other elements were chiefly negative in soil profile. 6.Although the total contents of elements of surface soil were lower in soil profile, the available contents and available /total ratio of it were higher. 7. Abundaning in Ca and higher pH value of limestone soil restricted the available contents and the available/total ratio of trace elements. In the end the contents of element in plants also were affected by the condition. So the contents of plants living in trace elements (Fe, Mn, Zn, B, Co, Cd, Ni, Cr, I, Sr) were lower than that living in red soil. Therefore the biological absorption of chemical elements was lower in limestone soil plants. Briefly, because the karst environment has rich Ca and higher pH value, by comparison with in region red soil, the system between soil and plant in limeston soil had it's respectively characteristic of element biogeochemistry.