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.