策勒沙漠-绿洲过渡带不同下垫面的输沙通量及粒度差异特征

Differences of sand transportation flux and sand grain size characteristics in different underlying surfaces on desert-oasis ecotone in Cele

沙漠-绿洲过渡带天然植被具有良好的防风阻沙效益,对绿洲内部农田起到重要保护作用。在策勒4个不同下垫面风动力条件研究基础上,结合地表和BSNE积沙仪沙样粒度进行分析,探讨不同下垫面水平输沙通量差异及沙物质粒度特征及形成原因。结果表明:平均风速及地表输沙率从流沙前沿经半固定沙地、固定沙地、进入绿洲后大幅度减少。沿主风向随着与流沙前沿距离的增加和搬运高度的增加,地表裸平沙地和输沙沙粒平均粒径都有变细的趋势,流沙前沿和绿洲边缘地表沙粒平均粒径相差30μm,BSNE跃移输沙沙粒粒级分布范围比过渡带平沙地地表沙粒粒级分布范围较窄。

Natural vegetation in desert-oasis desert plays important role in preventing against wind and intercepting active sand,which can protect effectively farmland in oasis as important function.Based on researching on wind power in different underlying land in oasis-desert ecotone in Cele and combined with analysis of sand particles on surface and sand transportation in sand trapping collectors,we analyzed the difference of sand transportation flux and grain size characteristics in different underlying surfaces and probed the causes.The outcome showed that the mean velocity and sand transportation amount decreased significantly from mobile sandy land to oasis along prevailing wind direction.Mean sand grain of bare sandy land surfaces and sand samples of traps showed trend to be finer with the distance increase from front mobile sandy land and height increase for BSNE traps,the mean sand diameter difference between mobile sandy land and fixed sandy land near oasis was 30μm.This explains that leaped sand transportation particles are concentrated in narrower granite size range compared with comparatively wider granite size of flat bare sandy land surface on ecotone.