关键词: 摩擦速度, 土壤类型, 土壤水分, 植被覆盖度, 有效粒度分布, 风蚀沙流通量

Abstract: In this paper a sensitivity test has been done to test each important impacting factor in Shao Yaping’s wind erosion model. Results indicate that this model can reasonably describe real natural wind erosion processes. The main modeling conclusions are as follows: ①With the wind increasing more stronger, much more sand particles within an enlarged particle size range can be initiated into saltation, and much more bigger dust particles can emit and suspend into the air with the stronger bombardments of saltating sands. But with the soil water content and the vegetation cover increasing, the particle size range of the saltating sand grains will become narrower and little bigger particles can be released into the air. ② The variations of the sand streamwise saltation flux with sand particle size Q(d) and the vertical dust emission rate with dust particle size F(d) are just similarly in phase with the available surface soil particle size distribution Ps(d) upon the surface of each soil type, which indicates that it is reasonable for former researchers to substitute the surface soil particle size distribution with the particle size distribution of the airborne sediments nearly over the surface under wind erosion conditions. ③If it is believed that wind erosion events take place only when the total sand saltation flux is raised to larger than 0.5 g·m^-1·s^-1, the threshold friction velocity (u*t) for each soil type of sand, sandy loam, loam, clay and silty clay to encounter wind erosion is approximately 0.3 m s-1 upon the dry, bare surface. With friction velocity (u*) equal to 0.6 m s-1, and soil water content (w) equal to zero, and discarding the total sand saltation flux less than 0.1 g\5m-1\5s-1, the vegetation cover (cf) must rise to 0.35, 0.45, 0.45, 0.55 and 0.55 respectively to hold back wind erosion events upon the 5 soil types of sand, sandy loam, loam, clay and silty clay. If the surface is bare and u*=0.6 m·s^-1, the soil water content (w) can’t hold back wind erosion events until it is up to 0.15, 0.18, 0.3, 0.36 or 0.33 for the soil type of sand, sandy loam, loam, clay or silty clay. ④Usually sand soil is most unready to release dust, and the dust emission rate of any dust particle size for sand soil is much less than that for other soil types even by 3~5 orders approximately. Silty clay soil is most ready to release dust and the mean size of the released dust is much smaller, so silty clay soil contributes much to dust transportation. ⑤The variation of the total dust emission rate (F) with wind and soil surface conditions is usually in phase with that of the total sand saltation flux (Q), that is, F is increasing with Q. ⑥Usually, with the friction velocity (u*) rising or the vegetation cover (cf) and the soil water content (w) dropping, the total dust emission rate (F) is increasing. But with the soil drag coefficient (sx) and its vertical elastic pressure (pye) enlarged, which indicates that the soil surface is seriously crusted, the dust emission rate F will be reduced greatly. ⑦Under usual wind erosion conditions, the dust emission rate (Fc) caused by the breaking up of aggregates and its sensitivity to various wind erosion conditions are both most large upon the surfaces of silty clay and sandy loam soils. But they are both most weak upon the sand soil surface.

Key words: friction velocity, soil type, soil water content, vegetation cover, available particle size distribution, sand saltation flux