Temporal variation in soil erodibility indices for five typical land use types on the Loess Plateau of China

Near soil surface characteristics of different land use types changed greatly during a growing season and thus likely affect soil erodibility index in arid and semi-arid regions. However, few studies have been conducted to quantify the temporal variations in soil erodibility indices under different land use types at small watershed scale. This study was carried out to detect the seasonal variations in soil erodibility indices reflected by soil cohesion (Coh), saturated conductivity (K,), the number of drop impact (NDI), the mean weight diameter of soil aggregates (MWD), soil penetration resistance (PR), soil erodibility K factor and a comprehensive soil erodibility index (CSEI) from different standpoints under five typical land use types (cropland, orchard, grassland, shrubland and woodland) on the Loess Plateau. The results showed that Coh, K-s, NDI, MWD, PR and K increased generally during one growing season for most of land use types. While, K was almost stable or decreased slightly under all five tested land use types. On average, CSEI decreased by 15.4%, 20.0%, 17.8%, 17.9%, 17.4%, 23.2% and 17.8% during one growing season for cropland, orchards of Juglans regia L. and Malus pumila Mill., grasslands of Bothriochloa ischaemum (L.) Keng, and Artemisia sacrorum Ledeb., shrubland and woodland. The variations in soil erodibility indices over time were attributed to the temporal changes in biological soil crust thickness, plant litter density, root mass density, soil organic matter content and soil bulk density during one growing season. The results demonstrate that the seasonal variation in soil erodibility need to be considered when soil loss is predicted in small watershed scale.

Automated summary

Seasonal variations in soil erodibility indices were detected in different land use types on the Loess Plateau, with soil cohesion, saturated conductivity, drop impact, soil aggregate size, penetration resistance, and erodibility index generally increasing, while erodibility K factor decreasing. These changes were attributed to variations in biological soil crust thickness, plant litter density, root mass density, soil organic matter content, and soil bulk density over the course of one growing season.