海南砖红壤的微形态特征以及南方网纹红土与砖红壤环境意义的差异

MICROMORPHOLOGY OF LATOSOLS IN HAINAN AND DIFFERENCES BETWEEN VEMICULATED RED SOILS AND LATOSOLS IN ENVIRONMENTAL SIGNIFICANCE IN SOUTH CHINA

主要运用土壤微形态学、粘土矿物学和土壤化学方法,对海南岛三个不同母质的砖红壤剖面的微形态特征和成壤过程进行研究,并将网纹红土和砖红壤进行比较。结果表明,砖红壤典型的微形态特征为易风化矿物颗粒和粘粒胶膜的缺失、均质状的b-垒结以及风化成因铁锰质结核的出现;典型的成壤过程为强烈的化学风化、红化、均质化、淋溶以及显著的脱硅富铝化过程。随着成土母质和土壤排水条件的变化,砖红壤的微形态特征亦有所差异。而我国南方的网纹红土的发育程度低于砖红壤,不宜被划分为砖红壤或氧化土,而更趋向归入老成土,在我国土壤发生学分类中大致相当于红壤。

Tropical soils with unique pedogenic processes influenced by warm humid climate are investigated worldwidely. Latosols 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, micromor- phological 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 Uhisols 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.