Spatial distributions of soil nutrients affected by land use, topography and their interactions, in the Loess Plateau of China

Soil nutrient availability and their spatial distributions are strongly related to land use and landscape morphology. This study aims to address the knowledge gap regarding the interaction between these factors and the underlying mechanisms. We selected five land uses (grassland with Artemisia gmelinii, woodland with Robinia pseudoacacia, shrubland with Caragana korshinskii and Hippophae rhamnoides, and apple orchard with Malus pumila) and nine slope positions across hillslopes in the Loess Plateau, China, to investigate their combined effects on the contents and stocks of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP). Parametric and non-parametric statistical tests were conducted to determine the significant differences in the means or the medians of the soil nutrient variables. Results showed that the SOC and TN contents of shrubland with Caragana korshinskii were statistically significantly greater than those of the grassland (p < 0.05). SOC and TN contents generally decreased from the upper slope to the middle slope, and to the foot slope for the grassland, woodland and shrublands, and on the contrary, an increasing trend from the upper slope, to the middle slope, and to the foot slope was identified for the apple orchard. This study highlights that land use, slope position and their interaction have significant effects on the spatial distributions of soil nutrients. It provides essential empirical evidence for the identification of the optimal vegetation type and slope positions in land management and vegetation restoration activities.