中国变性土的分布、特性和分类

DISTRIBUTION, CHARACTERISTICS AND TAXONOMIC CLASSIFICATION OF VERTISOLS IN CHINA

本文研究了我国主要变性土的区域分布、某些发生学特性和分类问题。研究结果表明:我国变性土及变性土型土壤有广泛分布,从热带、亚热带到暖温带。其共同的成土条件是:有一定干湿交替的气候、低平的地势、富含盐基的母质和粘重的质地。据估计,此类土壤约占全国总土地面积的1%左右。变性土是在特殊的地球化学环境和干湿交替的条件下形成的,深受地域性因素的影响,其成土年龄古老而发育程度较弱。一般变性土带有某些水成土的特征,而钙质变性土兼有水成土和钙层土但又不完全与它们相同的成土地球化学特点。所研究的11个剖面中,有8个属于中国土壤系统分类(首次方案)中的变性土土纲,其余3个则属于潮湿土土纲。

The paper deals with distribution, some genetic characteristics and taxonomic classifica- tion of main Vertisols in China. Eleven profiles from main areas of Vertisols in China were. studied. The research content included: (1) morphological features, physical and chemical properties, abundances of macro-elements and trace-elements, iron and manganese oxides and clay minerals of main soil genetic horizons; (2) chemical and mineralogical composition of iron-manganese concretions and calcareous concretions etc.The results show that Vertisols and Vertisol-type soils in China are distributed widely from tropical zone, subtropical zone to warm temperate zone, which could be roughly divided into three areas: (Ⅰ) tropical Udic Vertisol area, including two pell clay soil regions in depressed lowlands of basalt tablelands of the northern Hainan Island and Leizhou Peninsula; (Ⅱ) subtropical Udic Vertisols area, including three pellic and chromic clay soil regions in lowlands, basins and river terraces of souhern China, Yunnan-Guizhou Pleteau and Sichuan basin; and (Ⅲ) warm temperate zone Aquic Vertisol area, including three black clay soil regions in lowlands of Huaibei Plain, Shandong Peninsula Plain and Nanyang Basin. Their soil-forming factors are characterized by the alternation of wet and dry climate, low and flat terrain, parent material with abundant bases and heavy texture. The area of the soils was estimated at about one percent of the total land area of China.Vertisols are formed under conditions of special geochemical environment and alternation of wet and dry climate, being greatly affected by local soil-forming farctors. Once the soils formed, Vertisols always tend to 'self-perpetuating' and show some 'pedogenic inertia', which often results in the longer soil-forming time but weaker development degree of the soils. Gernerally speaking, Vertisols have some characteristics of Aquosols. In the soil-forming process, some variable valence dements, such as Fe, Mn, Co and Ni, thanslocate actively and for various iron-manganese concretions, nodules, rust streak, rust spot and so on. On the calcareous parent materials, meanwhile, Ca and Sr also translocate actively and form various carbonate concentrations, calcareous concretions or duripans. Therefore, calcareous Vertisols have some characteristics of both aquosols and Pedocals.Eight of all studied profiles belong to Vertisol order in CSTC (1st PROJECT) and also correspond with the criteria of Vertisols in 'Soil Taxonomy' (USDA, 1975) and 'Soil Map of the World' (FAO/UNESCO, 1988). Among all the profiles, two from tropical area (profile Ⅰ-1 from Qiongshan, Hainan and profile Ⅰ-2 from Xuwen Guangdong) belong to pellic clay soil group in Udic Vertisol suborder, two from subtropical area (profile Ⅱ-1 from Tiandong and profile Ⅱ-2 from Baise, Guangxi) belong to chromic clay soil group in Udic Vertisol suborder, four of seven profiles from warm temperate zone Shajiang black soil area belong to black clay soil group in Aquic Vertisol suborder, while the other three profiles belong to Shajiang black soil group in orthic Aquosol suborder under Aquosol order. One profile (profile Ⅲ-1-2 from Guoyang, Anhui) has Vertic features and belongs to Vertic shajiang black soil subgroup, while the other two profiles (profile Ⅲ-2-3 from Ningyang, profile Ⅲ-2-5 from Zibo, Shandong) do not have evident vertic features.