Soil erosion and deposition processes act as key drivers of soil resources distribution across landscapes, affecting soil quality and functionality. However, the impacts of long-term soil erosion on soil quality and degradation in the black soil region remain unclear. Here, we assessed soil quality and degradation as a consequence of historical erosion and soil redistribution in an agricultural catchment in Northeast China. Soil quality indices (SQI) were calculated using both linear and non-linear scoring function methods, along with soil indicator selection approaches, including Total Data Set (TDS) and Minimum Data Set (MDS). Soil degradation indices (SDI), resistance indices (SRI), and the change of SQI (CSQI) were computed and compared. The mean SDI for bulk density (BD) and sand was greater than 0. When BD and sand were excluded, the mean SDI and SRI for the 0–10 cm and 10–20 cm soil layers were −29.8% and −21.9%, and 0.57 and 0.65, respectively. Surface soil (0–10 cm) organic matter (SOM), available potassium (AK), structure stability index (SSI), and total nitrogen (TN) in eroding sites, as well as AK, SSI, SOM, TN, and available phosphorus (AP) in depositional sites, are particularly sensitive to long-term erosion. Field capacity, sand, AK, and SSI were selected to develop the SQI, with the non-linear method utilizing MDS outperforming other SQIs. Most SQIs in eroding sites were lower than those in depositional sites and increased with higher soil redistribution rates. The assessment of soil degradation using SDI, SRI, and CSQI revealed that long-term erosion markedly diminished soil quality, although deposition somewhat alleviated this impact. The lower SQI in the 10–20 cm compared to the 0–10 cm soil layer was primarily attributed to decreased FC, while long-term erosion degraded soil quality by negatively affecting AK and sand content. These findings enhance our comprehension of soil degradation caused by erosion in the Mollisol region of Northeast China.
Liu et al. (Thu,) studied this question.