2.1 Study area
The area targeted by this research is the Zhangbei County in the Hebei
Province, China (Figure 1; 40°03′ to 41°27′N, 114°20′ to 114°58′E). The
study area has a mid-temperate continental monsoon climate, with an
altitude ranging between 1600 m and 1800 m, an annual average
temperature of 3.2 °C, and an annual precipitation of approximately 300
mm. Relatively dry conditions have caused vegetation degradation in this
area (Sun et al., 2019). The study area has good wind resources and is
the main route through which the northwest monsoon goes south in winter
and spring. The annual average wind speed is approximately 6 m/s. In
average, there are 30 days in a year with wind speeds exceeding the Near
Gale (from international wind scale). The Zhangbei County belongs to the
typical agro-pastoral transition zone. The soil conservation measures of
the farmland are not perfect, which lead to soil wind erosion
occasionally.
Figure.1 Location of the study area. The
gray is the Hebei Province; the
purple region is Zhangbei County; and the red star is Beijing.