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

Abstract

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 (Ks), 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, Ks, 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.