摘要
根据成土年龄、土壤中植物孢粉鉴定、腐殖质组成、碳酸钙含量、粘土矿物类型、土壤微形态,土壤剖面形态和其它特征,分析了黑垆土的形成环境。研究表明,黑垆土是一种古土壤,它的许多特征是古生物气候条件的产物。
Base on the determination of soil age, spore-pollen in soil, composition of humus, soil micromorphology, X-ray diffraction, soil profile morphological character, soil physical and chemical properties, the genetic environment of dark loessial soil are discussed. The results show that dark loessial soil is a palesol. Many characteristics of dark loessial soil are the result of paleontology climatic conditions.^(14)C soil age. The genesis of dark loessial soil includes three year ranges: 8100—8500, 4600—7400, and 2000—3000 years B. P. , which were cold in the climate.Spore-pollen appraisal. According to the appraisal of spore-pollen in Xian, Luochuan, Ansai, Longxi and Xifeng, a conclusion can be drawn that the herb is predominant and the environment is cold and damp in the genetic period of dark loessial soil.Humus. The humus horizon of dark loessial soil is more than sixty to 100 centimetres, in which shows moist climate and luxuriant plants in the period of soil formation. The HA is as high as 40% of total carbon and HA/FA>2 in the dark loessial soil of the northeastern part of China, being quite different from other soils which have a HA/FA ratio of about 0.5 in the loess plateau.Content of calcium carbonate. Richment of calcium carbonate is a basic feature of loess in China (the CaCO_2 content is about 10%). According to the data obtained in the fifteen profiles of dark loessial soil in all parts of loess platean, 40 per cent have a CaCO_2 content of<1%, 35 per cent 2—3% and the rest profiles 5—10%, but the CaCO_3 content is 30—50% lower than that of loess. The leaching out of calcium carbonate has proved that there is much water moving along the profile during the formation of dark loessial soil.Chemical composition and molecular ratio. The molecular ratio of CaO to MgO (0.6—0.7) and CaO+K_2O+Na_2O/Al_2O_3(0.8—0.9) of dark loessial soil is smaller than those of loessial soil (2.5—2.7 and 1.7—1.9 respectively), but the K_2O/Na_2O ratio of dark loessial soil is greater than that of loessial soil (0.6—0.78). By contrast with loessial soil, the Fe_2O_3 content of dark loessial soil is slightly lower, the activity of Fe_2O_3 and the quantity of free oxides are higher but the CaO content is much lower. The aforementioned facts show that dark loessial soil^- is higher in humidity and intense in the leaching and forming processes, being of signifacance in indicating environment.Clay minerals. It is a sign of weakly developed soil that there is chlorite in soil. The chlorite content of dark loessial soil is lower than that of loessial soil, indicating relatively intense forming proess of dark loessial soil. Another feature of dark loessial soil is free of smectite, which is also a sign of better water regime in the soil. Soil micromorphology. There are more fine-grained matter and iron minerals but less calcite and carbonate capsule in dark loessial soil. These are related to the relatively intense weathering and greater leaching loss of carbonates.Other characteristics. There is a higher content of clay in dark loessial soil. The physical clay may reach 40 per cent in some of the soils, as a result of the deposition of clay carried in water movement.The profile of dark loessial soil is generally covered by a layer of loess which is the latest deposit and differs greatly from the dark loessial soil in color and physico-chemical properties. The existence of the overlaying horizon of loess clearly reflects the change of the environment in the formation of dark loessial soil.
出处
《土壤学报》
CAS
CSCD
北大核心
1992年第2期113-125,共13页
Acta Pedologica Sinica
关键词
黑垆土
环境
Dark Loessial Soil, Environment
