Spatial Contribution of Environmental Factors to Soil Aggregate Stability in a Small Catchment of the Loess Plateau, China

Abstract

Soil aggregate stability and erodibility are the influential factors governing soil resistance to water erosion. The interactions among aggregate stability, erodibility, and their influencing factors have not been fully explored. We collected soil samples from 0–10 cm and 10–20 cm layers in the Zhifanggou watershed. Then, the major contributors to aggregate stability and erodibility and how soil properties, environmental factors and land use contributed to them were explored by using partial least-squares regression and path analysis, respectively. The results showed that the major contributors included the slope, soil organic carbon (SOC), elevation, the percentage of landscape area of farmland (PLAND_F) and grassland (PLAND_G), the land surface temperature difference between seasons (ΔLST), topographic wetness index (TWI), pH, amorphous iron (poorly ordered forms of iron, Feo), and calcium carbonate (CaCO3). In which, the slope, SOC, and elevation were the most important contributors to the mean weight diameter (MWD) and the percentage of water-stable aggregates greater than 0.25 mm (WSA>0.25) and had a direct contribution to MWD, WSA>0.25, and K factors. The PLAND_F and PLAND_G had a significant and indirect contribution to those three indices by affecting slope. Meanwhile, the effects of pH, Feo, and CaCO3 on WSA>0.25 should also not be underestimated. For MWD and WSA>0.25, there was a significantly higher effect of the land use types and composition than hydrothermal conditions. For K factors, PLAND’s contribution was still higher than ΔLST and TWI, but they were all significant. The other soil properties, including pH, CaCO3, and Feo, indirectly affected them by influencing SOC. However, the direct contributions of soil properties increased as the soil layer deepened.