2.1 Study area
The study area is located in the Zhifanggou watershed (36°48’ N, 109°15’
E) in the loess hilly and gully region of northern Shaanxi Province,
China (Fig. 1). This area belongs to a typical forest-grass zone with
complex terrain, ravine and crisscross, and an elevation ranging from
997~1731 m. The region is mainly affected by the
semiarid continental climate in the warm temperate zone, with an average
annual temperature of 8.8 ℃ and an annual rainfall of 500-600 mm. The
natural vegetation of the area has been almost completely destroyed, and
the restored plantations are composed of Robinia pseudoacacia ,Populus simonyi , Caragana korshinskii, and Hippophae
rhamnoides . The abandoned slope is mainly composed of herbs at
different stages of succession, such as Artemisia gmelinii ,Artemisia Giraldi , Stipa bungeana , and Bothriochloa
ischaemum . The soil type is loessal soil, of which silt accounts for
over 64%. In this area, the soil is loose with poor soil resistance,
which leads to serious soil and water erosion.
In the watershed, typical land cover (forest, shrub, grass, crop, and
bare land) was selected (Table 1). The same slope gradient site was
chosen as the experimental plot (22°~25°), which was a
5×20 m standard experimental plot. In the forest plot, the major tree
species was Robinia pseudoacacia . Many herbaceous plants grow
here, such as Stipa bungeana , Setaria viridis , andLeymus secalinus . In the shrub plot, the main planted species wasCaragana korshinskii , with many undergrowth vegetation types,
such as Artemisia gmelinii , Bothriochloa ischaemum , andHeteropappus altaicus . In the grass plot, the dominant grass
species were Lespedeza daurica , Bothriochloa ischaemum ,Stipa bungeana , Artemisia gmelinii , andLeymus secalinus . In the crop plot, the major crop species wasSyringa oblata . The bare land plot did not have any plant growth
and was weeded once a month.