Micromorphology of Latosols in Hainan and environmental significance differences between vemiculated red soils in south China and Latosols

Abstract

Tropical soils with unique pedogenic processes influenced by warm humid climate are investigated worldwidely. 1atosols are zonal soils in tropical areas of China and have been the subject for scientists studying mineralogical and geochemical characteristics. However studies on micromorphological characteristics of the soil are still far and rare. In this study, micromorphological features and pedogenic processes of three Latosol profiles derioedfrom different parent materials from Hainan Island are studied with soil micromorphological, clay mineralogical and chemical methods. Vermiculated red soils in South China, which were formed in the mid-Pleistocene, are called Latosols in some studies. To provide evidence for the study of palaeoenvironment and archaeology, vermiculated red soils are compared with Latosols in this study. The results indicate that Latosols mainly have two typical micromorphological features. One is the absence of unweatherable minerals and illuvial clay, and the other is the presence of nodules of iron and manganese oxides resulting from weathering and isotropic b-fabric in good drainage conditions. The typical pedogenic processes of latosols are strong weathering, rubification, homogenization, eluviation and remarkable desilication. In poor drainage conditions, some pseudogley features are formed. Resulting from strong chemical weathering under the tropical climate, Latosols are strongly developed. Compared with Latosols, vermiculated red soils are less developed. They cannot be classified as latosols and Oxisols, but tend to be classified as Ultisols in the American Soil Taxonomy, corresponding to red earths in the Chinese Soil Genetic Classification. This indicates wet, warm climate and indeciduous, latifoliate vegetation in the vast areas south of the Yangtze River during the forming period of vermiculated red soils