Spatial heterogeneity of wind-eroded soil particles around Nitraria tangutorum nebkhas in the Ulan Buh Desert

Variation in grain-size characteristics of simulated shrubs as a novel sand-barrier in a wind tunnel experiment

Sand transport is the main manifestation of sand damage in the arid and semiarid regions globally. It is a huge challenge to stabilize mobile sandy and change them into stable productive ecosystems. The establishment of simulated shrubs is one of the most effective measures to solve the above difficulties as a novel sand-barrier. To clarify simulated shrubs' role in the process of ecological restoration. It will be greatly helpful to incorporate the shelter device proposed in the present work into landscape models for aeolian soil transport, to optimize the parameters associated with the sand-barrier characteristics for aeolian soil stabilization at the field scale. A series of wind tunnel experiments were conducted to analyze the variations of soil grain-size of simulated shrubs with different spatial configurations, row spaces, and net wind speeds. Further, the soil grain-size parameters were calculated by the classic method proposed by Folk and Ward to clarify the change of soil particles resulted from the blocking effects. The average grain-size content of simulated shrubs with different spatial configurations, row spaces, and net wind speeds was dominated by medium sand and fine sand, and the total percentage was more than 90%. Moreover, the sand deposition of simulated shrubs with different spatial configurations increased with the improvement of wind speeds. The average sand deposition of spindle-shaped simulated shrubs in 17.5 × 17.5 cm and broom-shaped simulated shrubs in 17.5 × 26.25 cm under different net wind speeds was the least. The effects of row spaces on average grain-size parameters increased with the improvement of net wind speeds. By calculating the correct characteristics of specific shelter devices proposed in the present work, all of these findings suggest that the application of simulated shrubs will be an important component to further extend ecological engineering projects in arid and semiarid regions.

Effects of Compound Sand Barrier for Habitat Restoration on Sediment Grain-size Distribution in Ulan Buh Desert

Wind erosion is a huge challenge for ecologists to stabilize sand dunes and to change them into stable productive ecosystems. In order to better understand its role in the process of ecological restoration, the sediment grain-size characteristics of compound sand barrier were evaluated through field experimental observation. The results indicated that the compound sand barrier was mainly composed of extremely fine sand and fine sand, and the fine sand and extremely fine sand in the inner side were higher than the east and west sides of the compound sand barrier. Due to the blocking effect of compound sand barrier, the Sorting Coefficient became better, the Skewness belonged to the positive deviation and the Kurtosis presented leptokurtosis distribution. Moreover, while the cumulative frequency distribution curve in the inner side became steeper, the slope increased and reached the top of the curve ahead of time. The effect of wind environment and vegetation coverage on the surface sediments showed that the average annual wind velocity and vegetation coverage was negatively correlated with the average grain-size, but positively correlated with the Sorting Coefficient. There was a significant correlation among the annual wind speed, vegetation coverage, average grain-size and Sorting Coefficient, which indicated that vegetation coverage and wind environment was the key factor leading to the difference of surface sediments in this area. Collectively, the establishment of compound sand barrier is one of the most effective methods of sand-fixing with engineering measure in the arid desert regions. Therefore, given the complexities of agricultural systems, stubble retention and black film covered during harvesting and incorporation of the stubble into soil in the next spring appears to be the best choice in the dry northern China where farmlands suffer serious wind erosion.