Response of soil erosion to vegetation and terrace changes in a small watershed on the Loess Plateau over the past 85 years

Land use on the Chinese Loess Plateau has undergone dramatic changes over the past few decades. The implementation of a series of soil and water conservation measures has significantly altered the soil erosion, transportation, and deposition processes on the Loess Plateau. To effectively address and mitigate soil erosion, it is crucial to accurately quantify the soil loss rate and analyze the contributions of soil and water conservation measures over the past several decades. In this study, the Zhifanggou watershed, located in the hilly area of the Chinese Loess Plateau, is utilized as an illustrative example. Using historical data, remote sensing imagery, and on-site data of soil, vegetation, and soil conservation measures, we assessed the soil loss rates from 1938 to 2022 based on long-term land use changes, utilizing the Chinese Soil Loss Equation (CSLE) model. Furthermore, we employed a quantitative evaluation to assess the impacts of vegetation change and terrace construction on soil erosion. The findings of our study reveal significant transformations in land use. Farmland experienced an initial increase followed by a subsequent decline, while the opposite pattern was observed for forest land. The simulated soil loss rate for the entire watershed exhibited an upward trend, rising from 34.86 t·ha−1·yr−1 in 1938 to 104.11 t·ha−1·yr−1 in 1958, before declining to 56.98 t·ha−1·yr−1 in 1999 and reaching 5.87 t·ha−1·yr−1 in 2022. Attribution analysis showed that vegetation change exerted a dominant influence on recent soil erosion dynamics, accounting for 86.10 % of the total contribution in 2022, while terraces contributed 13.90 %. These findings clarify long-term soil erosion mechanisms and provide guidance for watershed soil and water conservation management.