Abstract
The transport of eroded soil to rivers changes the nutrient cycles of river ecosystems and has significant impacts on the regional eco-environment and human health. The Loess Plateau, a leading vegetation restoration region in China and the world, has experienced severe soil erosion and nutrient loss, however, the extent to which vegetation restoration prevents soil erosion export (to rivers) and it caused nutrient loss is unknown. To evaluate the effects of the first stage of the Grain for Green Project (GFGP) on the Loess Plateau (started in 1999 and ended in 2013), we analyzed the vegetation change trends and quantified the effects of GFGP on soil erosion export (to rivers) and it caused nutrient loss by considering soil erosion processes. The results were as follows: (1) in the first half of study period (from 1982 to 1998), the vegetation cover changed little, but after the implementation of the first stage of the GFGP (from 1999 to 2013), the vegetation cover of 75.0% of the study area showed a significant increase; (2) The proportion of eroded areas decreased from 41.8 to 26.7% as a result of the GFGP, and the erosion intensity lessened in most regions; the implementation significantly reduce the soil nutrient loss; (3) at the county level, soil erosion export could be avoided significantly by the increasing of vegetation greenness in the study area (R = −0.49). These results illustrate the relationships among changes in vegetation cover, soil erosion and nutrient export, which could provide a reference for local government for making ecology-relative policies.
Highlights
Soil erosion export is the part of eroded soil that transported to rivers
We evaluated the soil nutrient loss before and after the Grain for Green Project (GFGP) at the county level by using a general model as follows: the GFGP (1990s), the soil erosion export and nutrient loss were calculated by the national survey of soil erosion at the county level during 1995–1996 (Yue et al, 2016); the vegetation changes were calculated by remote sensing data during 1982– 1998 with the methods described in section “Detecting Changes in Vegetation and Their Drivers.”
Where Econtent is the nutrient content in the soil unit, which was extracted from the Harmonized World Soil Database (HWSD) (Nachtergaele et al, 2009) and averaged by 0–30 cm at the county level
Summary
Soil erosion export is the part of eroded soil that transported to rivers. It is commonly calculated as the difference between the removal of eroded soil and the deposition of new soil (Yue et al, 2016). Vegetation Restorations Reduce Soil Erosion depth, nutrient availability and water holding capacity in the root zone (Yang et al, 2003; Du et al, 2019). Few retrospective assessments have been made to measure the amount of the retained soil especially the subsequently reduced soil nutrients losses by vegetation restoration for a whole period at the catchment scale. Accurately assessing the processes of nutrient exchange is critical for tracking nutrient migration and for studying its effects on other systems (Bouwman et al, 2013)
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