Changed surface roughness by wind erosion accelerates water erosion

Wind and water erosion are two dominant types of erosion that lead to losses of soil and water; understanding their interactions is important for estimating soil quality and environmental impacts in regions where both types of erosion occur. This study was devoted to investigate the characteristics of the surface roughness, runoff, and erosion rates under a one-way wind erosion-rain erosion sequence. The experimental setup included a wind tunnel and a rain simulator. Soil samples were collected from a sloped wasteland in Wuqi County, northern Shaanxi province, China. This experiment was conducted with wind erosion firstly and water erosion thereafter, with three wind speeds (0 [control], 11, and 14 m s(-1)) and rain intensities (60, 80, and 100 mm h(-1)). The physical properties of top soil samples (0-1 cm) were analyzed after each wind erosion test. The soil surface roughness (mm), runoff (mm h(-1)), and erosion (g m(-2) h(-1)) rates were calculated after wind and water erosion. Linear regression analysis was used to estimate the relationships between surface roughness, runoff rate, erosion rate, and erosion factors. Wind erosion increased the sand content in the top 1 cm of soil in simulation area by 6.51-6.74 % and decreased clay and silt contents by 7.65-9.15 and 17.94-18.15 %, respectively, relative to the original surface soil. Compared with the control, the wind erosion treatments increased the surface roughness, runoff, and erosion rates by 8.12-78.06, 4.5-21.69, and 7.25-38.97 %, respectively, at wind speeds of 11 and 14 m s(-1). The relationship between runoff and rain duration under different rain intensities after wind erosion were described well by a logarithmic function, whereas a large degree of variation was observed in erosion rate. The increased values of runoff and erosion rates in the different treatments, however, became weaker with increasing rain intensity, probably due to the much higher energy of the rain at the highest intensity, which decreased the proportional influence of wind erosion on the microtopography of the soil. Linear regression showed that surface roughness, runoff, and erosion rates were positively associated with wind speed and rain intensity (P < 0.01). Wind erosion clearly has the capacity to intensify water erosion. Results demonstrate the need for controlling of wind erosion to reduce water erosion in regions where both types of erosion occur. Moreover, a consideration of the impact of wind erosion on water erosion is required for effective erosion prediction in these regions.