Wind erosion forces and wind direction distribution for assessing the efficiency of shelterbelts in northern China

The prevailing wind erosion direction (PWED) and wind direction distribution (WDD) exert a significant impact on the protection efficiency of shelterbelts in regions affected by soil wind erosion. In this paper, wind erosion forces, the PWED, the preponderance of wind erosion forces (Rm) in the PWED, and the contrast of wind erosion forces between the PWED and the opposite direction (λ) were calculated based on wind data recorded at 204 weather stations in northern China from 1980 to 2016. The dominance of the PWED, reflected by the combination of Rm and λ, was defined as the WDD. The WDD was divided into four structural patterns: strong dominance of the PWED (Pattern I), strong dominance of both the PWED and its opposite direction (Pattern II), medium dominance of the PWED (Pattern III) and weak dominance of the PWED (Pattern IV). The western region mostly belongs to Pattern I, and in this area, primary shelterbelts perpendicular to the PWED should be strengthened. Local areas in the mountain passes in the northwest Junggar Basin, north Qaidam Basin, northwest Hexi Corridor, and southern part of the plains area in Northeast China belong to Pattern II, and multirow shelterbelts with orientations perpendicular to the PWED must be set up in this region. The east region mainly belongs to Pattern III or Pattern IV; different levels of shelterbelts must be set up, and both primary and secondary shelterbelt construction must be strengthened in this region.