Assessing impacts of ecological restoration project on water retention function in the Taihang Mountain area, China

Abstract

The ecological restoration (ER) project significantly affects the water retention function in the Taihang Mountain area. However, a comprehensive understanding of the water retention effects in different ER project areas still needs to be improved. In this study, we employed the integrated valuation of ecosystem services and trade-offs (InVEST) model to evaluate the differences in water retention among different ER project areas. Additionally, we used the structural equation model to explore the influence of various factors on water retention. The results showed the following: (1) The total amount of water retention in the Taihang Mountain area increased yearly from 2000 to 2020, with an 85.25% increase in 21 years. The water retention function showed a trend of transferring to a higher level. (2) The forest land restoration project showed the highest average water retention capacity, followed by the grassland restoration project, which together provided 61.12% of the water retention capacity in the ER areas. Forest land restoration project was found to have the most potential in improving water retention, while grassland restoration was more efficient. The water retention capacity of a 21-year-old artificial forest could only reach 70.92% of the natural forest. Cropland restoration mode increased the water retention by 22.85% compared with non-ecological engineering areas. (3) The enhancement of water retention function in the study area resulted from multiple factors, among which precipitation and root depth were the most critical variables. (4) According to the structural equation model, the impact of natural factors on water retention accounted for 74.33%, and ecological engineering had a greater impact on water retention in the hilly zone. The ER project significantly increased water retention capacity. The results provide scientific support for improving water retention function and optimizing ER projects in semi-arid areas of China.