Soil Erodibility Characteristics of Gullies With Typical Plant Communities on the Loess Plateau of China

Gully is widely developed over the world and becomes the major sediment source in small watersheds. With vegetation restoration, not only do the erosion type and intensity of the gully change and the morphology tend to be stable, but also the soil erodibility characteristics of the gully likely change considerably, attributed to the alternations in near soil surface characteristics of plant communities. However, few studies have focused on the variation in soil erodibility characteristics of gullies with different plant communities in semiarid regions. This study was carried out to determine the soil erodibility characteristics of gullies with typical plant communities and identify their dominant influencing factors on the Loess Plateau. Eight soil erodibility indicators (K factor (K), mean weight of diameter (MWD), mean number of drop impact (NDI), soil disintegration rate (SDR), soil cohesion (Coh), soil penetration resistance (PR), saturated hydraulic conductivity (Ks), and soil structural stability index (SSI)) were measured or computed to quantify the soil erodibility of the topsoil layer (0–5 cm). A comprehensive soil erodibility index (CSEI) calculated from eight erodibility indicators was applied to systematically reflect the soil erodibility characteristics. The results revealed that the soil erodibility indicators of the gully changed significantly with plant communities. From grass to shrub and forest community, the K factor and SDR of the gully increased, while MWD, NDI, Coh, PR, Ks, and SSI decreased. The gully with Robinia pseudoacacia Linn. (RP) community had the maximum CSEI. Compared to the forest community, the CSEI of the gully with grass and shrub communities decreased by 31.2%–60.4%. Soil capillary porosity (SCP), soil organic matter content (SOM), and root mass density (RD) were the dominant factors affecting the soil erodibility of gullies. CSEI decreased linearly with increasing SCP, SOM, and RD. The grass community is the most effective in reducing the soil erodibility of gullies, owing to the crucial function of root systems in this process. The results revealed the impacts of plant communities on soil erosion in gullies, helping optimize vegetation restoration modes of gullies in semiarid regions.