试论中国淋溶土的成土过程与基本特性

淋溶土是我国的一类重要土壤，总面积约１２．５万ｋｍ＾２。在我国现行的土壤分类系统中，有几个土类－暗棕壤、棕壤、酸性棕壤、白浆土以及部分褐土可归属于淋溶土＾１）。这些土壤大都是温带针阔叶混交林下的森林土壤，生物地球化学循环别具特征。据３０个剖面的统计分析，其Ｂ／Ａ层粘粒含量比值，从暗中壤－棕壤－黄棕壤，为１．４７－１．８８－２．５３，经统计土壤发育过程中粘粒的生成量（或损失量）相差七倍。上述几种土壤

PEDOGENIC PROCESSES AND CHARACTERISTICS OF ALFISOLS IN CHINA

Alfisols are important soils in China. They occupy about 1.25 million km² or about 13% of the land area. Dark brown forest soils, burozems, yellow-brown earths, and drab soils in temperate China are identified as four major great soil groups. According to the criteria given by soil Taxonomy, these soils should belong to Alfisols. Additionally, Baijiang soil is identified as a special kind of Alfisols, probably Albaqualfs. These are mostly forested soils with a return of organic matter, estimated at 5-13t/ha/yr, to the soils from a mixed temperate forest. In terms of elemental bio-cycling Ca is prominent.In a comparison of 30 profiles, the average rate of clay (B/A) was 1.47 for cryoboralfs and Eutroboralfs: 1.88 for Hapludalfs and 2.53 for Paleudalfs. From Eutroboralfs to Paleudalfs there was a difference of 7 times in the average gain (or loss) in clay during soil development. Hapludalfs, Cryoboralf and associated Cryaquepts differ considerably in the moisture regimes, but the amount of water is always enough to cause a significant leaching. During the weathering and pedogenetic processes-TiO₂, Mgo and Fe₂O₃ are accumulated, respectively, in both A and Bt horizons; But SiO₂ and Al₂O₃, tend to be leached from the solum.