WU Yanfei1,2, JI Hongbing1,3, CHU Huashuo1,2, LUO Gang1,2
(1. State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Science, Guiyang 550081, China;
2. University of Chinese Academy of Sciences, Beijing, 100049, China;
3. Civil & Environment Engineering School, Univerity of Science & Technology Beijing, Beijing 100083, China)
Abstract: The karst region in Southwestern China is one of the famous karst regions in the world. This region is considered to be an extremely fragile ecological environment due to its thin soil, slowly formation rate, coarse texture, and serious erosion, so it is vulnerable to desertification. Soil organic matter of karst area plays an important role in keeping regional soil and water, showing its critical importance in the research of karst ecosystem. We selected the typical soil profiles which located in the Yuntai Mountain, Shibing, Guizhou Province to analyze the soil organic carbon (SOC) content and soil physical-chemical properties (SPCP), and then studied the coupling relationship between each other. Our results indicate that soil pH values are mainly concentrated in the range from 7.50 to 8.00, alkaline, and the soil is alkaline calcareous soil with the color of black-brown-yellow. Based on the soil grain size fraction of the three profiles, it shows that the components are mainly distributed in the range from 1μm～50μm, which are consisted of the coarse clay, silt and coarse silt. Other components especially located in the range of coarse silt, which particle size range of 10μm～50μm, and almost all of the soil samples in this part within the scope of volume percentage of higher than 50%. The soil texture is silty clay loam. Overall, there are no big differences in compose of clay, silt and sand soil in the three calcareous soil profiles, indicating that they developed from the same parent rock and under the same conditions. However, there is an obvious difference in the particle size distribution characteristic for the same level of different soil profiles or the same soil profile of different levels, based on the influence of soil physical and chemical conditions, weathering degree and hydrogeology conditions. It is also found that the SOC content range is between 1% and 11%, with high variability, and decrease rapidly with increasing deep of soil profile. It’s content mainly concentrated in the surface soil layer. Vegetation, soil physical and chemical properties and profile evolution have important effect on SOC. As shown by our results, significant and negative correlations were found between SOC and parameters of soil bulk density and pH value (R2=0.62, 0.21, n=32). On the contrary, SOC has a very significant linear positive correlation with soil organic nitrogen (R2=0.98, n=32). Besides, SOC has weak correlation with different particle size composition, and relatively maximum negative correlation with soil clay. As obviously manifested by these results, SPCP can affects the content of SOC in a great extent, in turn, the change of SOC can adjust the SPCP. The two factors contact each other, mutual coupling, and restrict the evolution of karst ecosystem.
Key words: Soil physical-chemical property; Particle size distribution; Soil organic carbon; Correlation analysis
EARTH AND ENVIRONMENT Vol.45, No.3, Tot No.317, 2017, Page 267-276
