Experimental study on the effect of four single shrubs on aeolian erosion in a wind tunnel

Abstract

Local plants are the most effective elements to control aeolian erosion but their effectiveness requires evaluation. A series of wind tunnel experiments were conducted to monitor the effectiveness of four single shrubs, Nitraria tangutorum, Haloxylon ammodendron, Calligonum mongolicum, and Hedysarum mongolicum, in reducing wind speed and sediment transport. Sediment flux was measured at x/h = 1 (h is the height of plant) and wind speeds were monitored at x/h = -2, −1, 1, 2, 3, and 5 in wind speeds of 6, 8, and 10 m s−1. An area of 1 m2 was scanned with and without plants to obtain bed microtopography change before and after wind application. The results showed that a sheltered zone of 5 h was observed downwind of the plants. N. tangutorum, H. ammodendron, C. mongolicum, and H. mongolicum decreased wind speed by 40%, 25%, 30%, and 40%, and blown sediment about 60%, 40%, 35%, and 30% respectively. The greatest sediment erosion (–33 mm) and lowest sediment deposition (11 mm) occurred with H. mongolicum. The lowest sediment erosion (-11 mm) and greatest sediment deposition (36 mm) were observed with N. tangutorum. The plants presented similar effectiveness in reducing wind speed in low wind speed (6 m s−1) but the difference between the plants became apparent in moderate (8 m s−1) and high (10 m s−1) wind speeds which were attributable to their different morphology. N. tangutorum had the greatest effectiveness in reducing wind speed and sediment transport especially close to the ground surface, associated with its optimum porosity (20%) and morphology.