Effects of Wind Velocity and Aggregate Size on Wind Erosion Characteristics of Loose Subsoil From the Mollisols Region of China: A Wind Tunnel Assessment

ABSTRACT: Soil erosion is a severe form of land degradation that threatens food production, especially in Northeast China, where fertile Mollisols dominate the agricultural landscape. Most previous studies have quantified soil erosion by water, while wind erosion of severely water-eroded areas with exposed loose subsoil remains rarely explored. Here, we present a wind tunnel experiment (75 measurements) with different wind velocities and aggregate size classes (<53, 53-250, 250-850, and 850-2000 μm) to assess the wind erosion behavior of loose subsoil. Free-stream wind velocities of 10, 12, 14, and 16ms^-1 resulted in shear velocities ranging from 0.15 to 0.75 ms^-1. The variation of shear velocity depended on the interaction between free-stream wind velocity and the surface roughness as influenced by aggregate size (R² = 0.40). The maximum aggregate size was also a good predictor of threshold velocity (R² = 0.84). Moreover, mass flux at higher elevations increased with wind velocity for both the 53-250 and 250-850 μm groups, whereas near-bed behavior varied by aggregate size. The second-finest fraction (53-250 μm) always exhibited an obvious peak in mass flux with height. The peak height increased slightly from 3 to 5 cm with increasing wind velocity. The second-coarsest fraction (250-850 μm) developed a pronounced peak height only at the highest wind velocity (16 ms^-1). These wind tunnel experiments on sieved loose subsurface soil materials indicate potential wind-driven transport. They also demonstrate that sever water erosion may additionally increase wind erosion and should be avoided to safeguard soil resources and food security.