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.