高级检索+

乌兰布和荒漠绿洲风沙特性及防护林防护效应

Wind-sand characteristics and prevention effect of shelterbelt in Ulan Buh desert oasis

  • 摘要: 农田防护林在保持水土及土壤风蚀防控方面发挥着重要作用。为了探究真实大气环境下绿洲防护林体系的防风阻沙效益,以乌兰布和荒漠绿洲防护林为研究对象,利用位于荒漠绿洲过渡带和绿洲的近地面沙尘观测塔监测的2019—2020年不同高度处的风速、风向和沙尘数据,分析荒漠绿洲过渡带和绿洲的风沙分布统计特性。结果表明:荒漠绿洲过渡带和绿洲主导风向为东北和西南方向,2区域内平均风速均随观测高度增加逐渐增大;从荒漠绿洲过渡带至绿洲,受防护林体系的影响, 平均风速整体减弱,≥4~8 m/s的中风速和≥8 m/s的高风速样本比例平均减少约8.8%和7.8%;荒漠绿洲过渡带和绿洲月最大平均风速多出现在夏秋2季以及春季末,且月最大平均风速与平均风速均值呈线性关系;2区域沙通量随着高度的增加逐渐减少,受防护林带影响同观测高度水平沙通量和垂直沙通量分别减少65%和36%;输沙方向整体朝东和东南偏东方向,该方向在绿洲受观测高度影响较小,在荒漠绿洲过渡带不同高度输沙方向会产生差异,输沙势从荒漠绿洲过渡带至绿洲总体降低。防护林体系对区域范围内的风沙活动影响明显,能够减轻风蚀所带来的水土流失,对绿洲可持续发展具有重要价值。

     

    Abstract:
    Background Farmland shelterbelt plays an important role in keeping soil and water and controlling wind erosion. In recent years, with the development of technology, the research of effectiveness on shelterbelts for prevention wind and resistance sand has gradually been various. Although a large number of researches have been investigated, the research of wind-sand characteristic on field measurement in a region area is necessary, due to the different structure of shelterbelts and topography in other regions.
    Methods Based on the data of wind speed, wind direction and sand monitored by two towers located in desert-oasis transition zone and inside oasis in Ulan Buh desert from 2019 to 2020, the characteristics of wind field and sand movement was analyzed through using statistical methods. Combined the wind speed and sand transportation at 9 different measurement heights and times, the relationship of wind-sand and height, time and space were explored.
    Results 1) The wind direction is dominated by northeast and southwest directions with frequency percentage of 14% and 13% in the desert-oasis transition zone, and with the percent of 12% and 11% in the oasis, respectively. 2) The mean wind speed gradually increased with measurement height in both of desert-oasis transition zone and inner area of oasis. Prevented by shelterbelts, the mean wind speed decreased from the desert-oasis transition zone to inner area of oasis. The records of wind speed decreased about 8.8% and 7.8% when the wind speed in ≥4-8 m/s and ≥8 m/s, respectively. 3) The monthly maximum mean wind speeds in desert-oasis transition zone and inner area of oasis reached peaks in summer, autumn and the end of spring. From the desert-oasis transition zone to oasis, the proportion of summer wind speed in the northeast (NE) direction decreased from 20% to 15%, and the proportion of winter wind speed in the southwest (SW) direction decreased from 20% to 16%. Meanwhile, the monthly maximum mean wind speed showed a linear relationship with the mean value of wind speeds. 4) The sediment fluxes in both regions had the decreasing tendency with the increase of observation height. Affected by the shelterbelt, the decreases of horizontal sand flux and vertical sand flux in the same observation height were 65% and 36%, respectively. The sand transportation was dominated by east and east-southeast directions in both regions. This tendency was less affected by observation height in oasis, but may be changed in different heights in desert oasis transition zone. Drift potential decreased from desert-oasis transition zone to oasis.
    Conclusions Shelterbelts systems in desert oasis has obvious influence on the wind and sand activities in the regional scale, and can reduce the soil and water loss caused by wind erosion. This result may provide a scientific basis for the optimization and adjustment of the shelterbelt effectiveness. It has great value to maintain the sustainable development in oasis.

     

/

返回文章
返回