Introduction
Soil erosion, a serious environmental problem of global concern, leads
to land degradation, which seriously affects sustainable agricultural
development. The total area of the Loess Plateau suffers from serious
soil erosion, with about 472,000 km2 of its 640,000
km2 erosion-prone and about 80% of the cropland area
suffers from moderate to severe erosion (Meliho et al., 2019). The Loess
Plateau is also a key area for soil and water conservation and
ecological security construction in China (Huang, 2021; Zhang, 2016).
Soil erosion restricts the sustainable development of the regional
economy and society and determines the evolution of the Yellow River and
its downstream safety (Fan et al., 2012). Soil erosion causes
irreversible soil degradation, leading to topsoil losses and the
migration of sediments (and associated nutrients) to water bodies,
decreasing the available farmland area (Molina et al., 2012). Excessive
sediments and pollutants lead to river siltation and ecosystem
degradation, endangering regional food security and ecological
environment quality. Thus, there is a need to understand the soil
erosion status of the watershed through soil erosion assessments and
mapping and determine the key areas for controlling soil erosion on the
Loess Plateau. The general loss equation of soil erosion can calculate
and analyze the distribution of soil erosion in watersheds. Various
studies have used more than 30 soil erosion models to assess soil
erosion rates on the Loess Plateau, with the common models usually
divided into empirical models [MUSLE (Luo et al., 2015), RUSLE (Feng
et al., 2010)] and physical models [WEPP (Han et al., 2016; Shen et
al., 2009), SWAT (Shen et al., 2009), WATEM/SEDEM (Feng et al., 2010),
Yang’s model (Yang et al., 2011)].
The soil erosion models mentioned above are generally not suitable for
the Loess Plateau because: (1) some are based on the revised general
soil loss equation, RUSLE, which is not suitable for the unique terrain
of the Loess Plateau with vertical and horizontal ravines and ignores
the impact of important soil and water conservation engineering measures
on erosion (MUSLE); (2) the function model obtained from experimental
data in a certain area can not be used in other areas (Yang’s model);
(3) physical models require high-quality parameters and verification
data, which is difficult to obtain in areas where little or poor quality
data is available (WEPP, SWAT). Liu et al. (2002) considered the
characteristics of soil erosion terrain on the Loess Plateau and
proposed an LS(Slope length and slope factor) algorithm suitable for the
region. Combined with the influence of human activities, they proposed
incorporating biological measures (B factor), soil and water
conservation engineering measures (E factor), and soil and water
conservation tillage measures (T factor) to improve the applicability of
the CSLE model on the Loess Plateau. This model is used widely in the
region due to its relatively simple structure, high accuracy, and easy
access to parameter factors, enabling rapid and comprehensive soil
erosion assessments at different temporal and spatial scales. Shi et al.
(2018) modified the CSLE model using runoff data from three different
watersheds on the Loess Plateau over three different periods
(1956–1959, 1973–1980, 2010–2013) to predict soil losses accurately
at the farmland scale. Duan et al. (2020) used the CSLE model and 0.5 m
Worldview satellite images, combined with soil and water conservation
engineering practices to estimate soil looses in China and the erosion
modulus and soil erosion intensity in Yunnan Province, a mountainous
area in southwest China. Liu and Liu (2020) used satellite remote
sensing image interpretation to understand land use changes in a small
watershed in southern China from 1989 to 2015 and the CSLE model to
calculate the contribution rate of soil erosion change and gully erosion
to sediment yield.
Since the 1970s, numerous soil and water conservation projects have been
undertaken on the Loess Plateau, such as the Converting Farmland to
Forest Project (1999–2010), the construction of check dams, and
improvements to sloping land (Fang et al., 1993). The continuous
development of soil and water conservation and governance has
significantly improved soil erosion and the ecological environment on
the Loess Plateau, changing the spatial pattern of land use (Zhao et
al., 2022). Land use and management affect runoff and sediment transport
by changing the surface morphology, the dominant factor associated with
soil erosion (Fu et al., 2020). The hilly and gully area of the Loess
Plateau is the most severely eroded area. Extreme rainfall events and
changes in land use patterns in recent years have setback the soil
erosion improvements (Li et al., 2022). Using soil erosion models to
assess soil erosion changes under the LULCC will help understand the
governance effects of previous engineering measures and the evolution
process of soil erosion to formulate future spatial pertinence and
sustainable land management and restoration strategies. However, few
studies have assessed soil erosion in the background of LULCC using CSLE
in the hilly and gully area of the Loess Plateau. Therefore, considering
the superiority of the CSLE model and changes in land use in the recent
ten years (2010–2020), we evaluated: (1) temporal and spatial changes
in soil erosion factors in the CSLE model for the Jiuyuangou watershed,
a typical watershed in the hilly and gully
region of the Loess Plateau, from
2010 to 2020; (2) temporal and spatial dynamic evolution of soil erosion
under land use change in the study area from 2010 to 2020; (3) the
spatial correlations between the soil erosion change and LULCC. our
study will provide a scientific reference for land use management and
ecological restoration projects in the basin.