A STUDY ON RECENT PEDOGENIC PROCESS AND ITS DEVELOPING AGE OF RED SOILS IN CHINA
Zhao Qiguo (Nanjing Institute of Soil Science, Chinese Academy of Sciences)
In order to further expound recent pedogenic process and developing age of red soils in China, a long-term stationary investigation on the basis of the past work has been conducted since 1984 by using parameters and computer simulation methods to carry out in depth dynamic and quantitative study on the effect of various vegetations and parent materials on the development of red soils. Preliminary results have been obtained as follows: 1. The pedogenic process of red soils in China is the result of interactions between desilicification-allitization process and biological enrichment process. The former is the base of red soil pedogenesis and in close relation to the formation of the ancient weathering crust of red soils, while the latter is the process of recent biological enrichment affecting the development of red soils. The influences of these two processes on red soll pedogenesis are mutually integrated and inseparable. 2. The long-term stationary investigation revealed that though red soils in China have undergone prolonged ancient weathering process, the current bioclimatic conditions display significant impact on its formation and reflect the characteristics of the recent pedogenic process of red soils in China, which suggests that under the current bioclimatic conditions, red soil desilicification-allitization and biological enrichment are still in process. The finding is of important theoretical and practical significance in further clarifying the substance of red soil formation and utilizing reasonably the red soil resources. 3. Calculation of the element migration conceptual model based on Si concentration in soil solution has preliminarily attained the absolute and relative ages of red soils derived from 4 different parent material in South China. If the geological age of the red soil (also termed as latosol) derived from basalt is taken for comparison with the past findings of geologists, completion of desilicification process in this soil takes 1.5 Ma, which equals roughly to the geological period of late Lower Pleistocene. This result is fairly in conformity with the conclusion of similar studies in the past.