where \(W_{f}\) is the total wind factor (\(m^{3}/s^{3}\)); \(\rho\) is
the air density (\(kg/m\)); \(g\) is the acceleration due to gravity
(\(m/s\)); SW is soil wetness (dimensionless); SDis the snow cover factor; Sa is the sand content
(5.5%–93.6%); Si is the silt content (0.5%–69.5%);\(Sa/Cl\) is the sand to clay ratio (1.2%–53.0%); OM is
organic matter (0.18%–4.79%); \(\text{CaCO}_{3}\) is calcium
carbonate
(0.0%–25.2%); Cl is clay content (0.32%–4.74%);\(\text{SLR}_{f}\) is the flat residues; \(\text{SLR}_{s}\) is the
standing residues; and \(\text{SLR}_{c}\) is the crop canopy. In this
study, the crop seedlings that provide partial canopy cover and protect
the soil were calculated as the effects of vegetation cover on wind
erosion.
2.3 Statistical methods
2.3.1 Trend analysis
Sen’s slope analysis method was used to calculate the soil wind erosion
trend between 1991 and 2015. This method is a non-parametric test that
only requires the independence of sample data and does not need to fit
the normal distribution (Gilbert, 1987). The trend degree, \(\beta,\) is
defined as follows: