Scale Effect Analysis of the Influence of Land Use Types and Environmental Factors On Soil Nutrients: A Case Study in Loess Areas in Northern Shaanxi, China.

Soil nutrient levels are important indicators of soil fertility, and various land uses and environmental factors can affect the spatial variation of soil nutrients. Soil properties vary with spatial and temporal continuity and soil possesses spatial heterogeneity when observed on either a small or large scale. This spatial variability has a direct influence on the productivity of soil as well as on the requirements and methods of ecological restoration. The spatial heterogeneity of soil is influenced by many factors, such as the parent material, climate, vegetation, topography, and human aspects. Many studies have suggested that the main factors that influence the spatial heterogeneity of soil exhibit significant differences on various scales Studies that focus on the differences in the spatial distribution of soil nutrients and the relationship between land use and environmental factors are valuable for the investigation of ecosystem processes. Typical small watershed and catchment areas in the loess hill and gully region of China were used as a case study. On the basis of experimental sampling in the field, we applied classical statistics and a canonical correspondence analysis (CCA) to study the relationship of the distribution of soil nutrients with land use and environmental factors at two different scales. The results indicate that the content of organic matter and NPK (i.e., nitrogen, phosphate, and potassium) is relatively high in wild grassland, woodland, and shrub land areas. The relationship of land use and environment factors to soil nutrient levels varies at different scales. In the Muyu small watershed area, the importance of the influence of land use and environmental factors on soil nutrients was ranked as follows: land use type>vegetation coverage>slope position>slope>relative elevation>aspect. In the Ansai catchment area, the importance was as follows: land use type>slope>vegetation coverage>aspect>relatively elevation>slope position.