Seasonal dynamics of soil rill erodibility under wheatgrass and switchgrass vegetation in the hilly-gully region of Loess Plateau

In order to evaluate soil and water conservation status in the restored grasslands in “Grain for Green” history in the hilly-gully region of Loess Plateau, wheatgrass and switchgrass plots were studied. The scouring experiments were carried out in a laboratory to simulate soil detachment by concentrated flow under six slopes (S=17.36%~42.26%) and discharges (Q=1.0~2.5 L·s-1). Soil rill erodibility (Kr) was estimated by WEPP model. The seasonal dynamics of soil rill erodibility under wheatgrass and switchgrass vegetation were studied during the growing season. Soil rill erodibility under wheatgrass in the hilly-gully region of Loess Plateau varied significantly with season (P<0.05), revealing a significant decline during the growing season. In contrast, soil rill erodibility under switchgrass cover had no clear seasonal dynamics during the growing season (P>0.05). Kr values in wheatgrass plots varied from 0.002 1 to 0.022 4 s·m-1. Soil rill erodibility in switchgrass displayed a pattern of seasonal dynamics, including an initial increase, followed by decline. Kr values in switchgrass plots varied from 0.003 2 to 0.021 9 s·m-1. The seasonal dynamics of soil rill erodibility of wheatgrass and switchgrass were affected by seasonal changes in soil cohesion, water-stable aggregate content, and grass root density. Significant negative correlation between soil rill erodibility and soil cohesion, water-stable aggregate content, and grass root density were found. In addition, the dynamics of change in soil rill erodibility of wheatgrass and switchgrass plots could be predicted based on with soil cohesion and grass root density. The growth of grass root system and the seasonal change in soil cohesion emerged as the main factors affecting the dynamics of soil rill erodibility of the restored grasslands in the hilly-gully region of Loess Plateau. Soil rill erodibility of the two types of grasslands showed significant negative correlation with soil cohesion and water-stable aggregate content, which are important parameters for simulating the dynamics of soil rill erodibility of the restored grasslands in this region.