乌兰布和沙漠天然灌丛防风阻沙效益研究

对乌兰布和沙漠封沙育草带内的天然灌丛周围风速及输沙量的野外观测结果表明,天然白刺灌丛沙堆对风沙流具有阻滞作用,风沙流在迎风面受阻堆积,在背风面风速下降40.3~42.1%,并形成低速区,引起沙粒堆积;沙蒿灌丛对2m高处风速没有影响,但可引起灌丛背风面近地表0.5m处风速下降20.5%。灌丛的迎风面存在一个减速区,灌丛顶部及两侧为加速区,灌丛背风面存在一个静风区和一个尾流区。灌丛侧面的输沙量最大,背风面输沙量最小,迎风面2H处输沙量大于1H处,这与各点的风速变化是一致的。对不同盖度沙地的输沙量进行的观测表明,输沙能力随植被盖度的增加而减小,流动沙地输沙量最大,在5.6~9.4m/s风速范围内输沙量为2.25~21.75g,半固定沙地的输沙量次之,为0.32~13.58g,固定沙地最小,为0.06~2.29g。

Study on Wind-sand Defending Effect of Natural Shrubs in Ulan Buh Dsert

Wind velocity and sand -transporting quantity around natural single shrub were measured in Ulan Buh desert. Results showed that natural Nitraria fangutorum shrubs have the function of blocking wind - sand flow. On the leeward side, wind velocity declined 40.3 - 42.1%, and lead to accumulating sand. Artemisia sphaerocephala shrub cannot influence the wind velocity on the height of 2m, but it can make the wind velocity on the height of 0.5m reduced by 20.5%. There is a slowdown area on the windward side of shrub, and velocity on the top and two sides of shrub are accelerated, while on the leeward side there are calm region and wake region. On the side of the shrubs, sand - transporting quantity is the most, while, on the leeward side, it is the least, and on the windward side, the one on 2H is more than the one on 1H. In addition, sand transport capacity decreases with vegetation coverage. The sand transporting quantity in shifting sandy dune is the most, which is 2.25 - 21. 75g during wind velocity of 5.6 - 9.4m/s, in sem - fixed sandy dune it is 0.32 - 13.58g, and the one in fixed sandy dune is the least, which is 0.06 - 2.29g.