沙面结皮形成与微环境变化

Crust formation on sand surface and microenvironmental change

研究结果表明沙坡头地区的大气年降尘(d<O.063mm)厚度平均为0.144mm.降尘中的悬浮盐粒、碳酸钙、微量元素以及低等植物、微生物和植物残体所提供的有机质可促进微环境的物理、化学和生物的综合作用,降雨量及其频率对结皮形成与成土过程影响较大.在粒径为0.250—0.125mm的沙丘中,降雨渗透率为1:7—1:10。结皮形成可改变近地层的水热状况,以致沙层含水量下降到2％以下,在一定程度上抑制了植物固沙的功能。

Investigation shows that in Shapotou region,the annual mean thickness of fallen dust(d<0. 063mm) is 0. 144ram. Its suspended sal particles,calcium carbonates,trace elements and organic matters originated from lower plants,microbes and plant residues can promote the physical, chemical and biological changes of microenvironment. The amount and frequency of precipitation strongly affect the crust formation on sand surface and soil forming process. In sand dune with grain size of 0. 250-0. 125 mm,the permeating rate of precipitation is 1:7-1:10. Crust formation on sand surface can induce the change of moisture and heat status near earth surface,and hence, decrease the moisture content of sand layer to 2％ or below,which limits the function of vegetations in sand stabilization to certain extents.