Relationships between the rock and soil chemical element contents and rocky desertification difference in karst rocky desertification process：A case study on the Zhenfeng-Guanling Huajiang area of Guizhou Province

The Zhenfeng-Guanling-Huajiang rock desertification demonstration area is a typical karst canyon in Guizhou, where the water and soil losses are serious and many places have suffered from intense rocky desertification. In order to study the intensity and diversity of rocky desertification in the area, 11 rock and soil samples from the 11 quadrats in the demonstration were collected and their chemical compositions were analysed. The results show that, (1) When the ratio of CaO/MgO in rock is larger and ratio of Rb/Sr is lower, the level of rocky desertification is higher. It means the strength of rocky desertification increases with the ratio of CaO/MgO increasing, and reduces with the ratio of Rb/Sr increases. (2) In the process of carbonate rock dissolution and weathering into the soil, Ca and Mg ions in rocks are taken away. As a result,their contentsin the rock are accordingly reduces, while the content of Mg ion in soil increases in intense rocky desertification areas. (3) The degree of chemical element loss and concentration has slightly differences in different rocky desertification areas. Generally the content instrong and potential rocky desertification area are higher than the mild and moderate rocky desertification area. (4) The ratio of Rb/Sr in the soil is higher, the degree of rocky desertification is more intense, that is the ratio of Rb/Sr increases with the intensity of growing rocky desertification. According to the different chemical elements in different rock desertification areas, this work studies the mechanism of water and soil loss in this area, which provides theoretical and practical basis for research of the water and soil loss and rocky desertification control in the demonstration area.