黄土高原土壤干燥化问题探源

ESSENTIAL EXPLORATION OF SOIL ARIDIZATION IN LOESS PLATEAU

以黄土沉积环境的旱化和黄土形成的三种风化类型为切入点 ,通过古今类比分析 ,探究了黄土高原土壤干燥化的黄土地质渊源。其次 ,讨论了土壤干燥化的土壤物理学成因。土壤水分物理特性 ,因受黄土粒度组成的制约而呈现出明显的方向性变化 ,即从西北向东南 ,土壤持水性能渐次增高 ,土壤蒸发性能渐趋降低 ,以田间持水量作为参照状态 ,则会发现黄土高原土壤经常处于水分亏缺状态。土壤干层的形成是干扰和破坏植物演替序列及其土壤水分生态基础造成的后果 ,从而引起土壤干燥化的趋强化发展 ,最后 ,从气侯变化入手 。

Soil aridization has turned in to an important restric ted facto r on ecological construction in Loess Plateau. It is believed that loess in China is an indicator of the arid and semiarid climate. The development of loess deposition is a symbol existing the general tendency of climate aridization in North China from the Early to the Late Pleistocene. Loess as the parent material of mod ern loess soil has a significant influence on soil development and its propertie s can be reflected in modern loess soils. Taking environment aridization with lo ess deposition and three weathering type of loess formation as a starting point, loess geologic origin of soil aridization in Loess Plateau was explored through comparative analysis between the old and present time. Soil physical cause of s oil aridization is discussed in the paper. Soil aridization in Loess Plateau is the result of common influence of transient and immanent condition. Soil water p hysical properties, including water retention property and evaporation property, show an obvious regional directional change dealing with loess grain size compo sition, It means that soil water retention property gradually increases and soil evaporation property gradually drops from northwest to southeast. If the field capacity is taken as an index, and then soil water deficiency is discovered freq uently in Loess Plateau. Arid soil layer is the ecological aftermath of strengt h ened soil aridization resulted from the disturbing and breaking alignment of pla nt succession and ecological foundation of soil water. Based on analysis of clim ate change, prediction of soil aridization tendency in Loess Plateau is presente d in the paper.