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說到世界上最輕的木材,那就不得不提到生長在美洲熱帶森林里的輕木,也叫巴沙木。這種樹四季常青,樹干高大。葉子像梧桐,五片黃白色的花瓣像芙蓉花,果實裂開像棉花。它非常地輕,比用來做軟木塞的栓皮櫟還要輕兩倍,我們做火柴捧用的白楊還要比它重三倍多。
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Due to interference of vegetation by experiment in wind tunnel and observation in field,the boundary layer is divided into 2 sublayers approximately at the vegetation height.As for the vertical wind gradient,it changes disorderly in rough sublayer of the lower and changes regularly in inertial sublayer of the upper varying with vegetation characteristics.Erosion rate increases exponentially with vegetation coverage reduction.The establishment of shrub shelterbelt along Tarim Desert Highway made obvious effects not only on wind preventing and sand binding,but also on microclimate.Compared with mobile dune,air temperature is higher in summer and lower in autumn,while relative moisture is higher,and evaporation and soil temperature lower in the shrub shelterbelt.