Trade-off Between Soil Water Maintenance and Carbon Sequestration During the Implementation of Ecological Restoration Programs in the Semi-Arid Loess Plateau

The conversion of degraded ecosystems to perennial vegetation in water-limited regions creates conflicting demands for soil water maintenance and carbon sequestration. However, current understanding of these competing demands is limited. In this study, to quantify the trade-off resulting from land-use conversion (converting cropland into forest, shrub, and grassland) in the Loess Plateau, 2775 observations of soil organic carbon (SOC) stocks (to a depth of 100 cm) and 2654 observations of soil water storage (SWS) (to a depth of 500 cm) from peer-reviewed papers and measured data were synthesized. The results showed that (1) land-use conversion greatly influenced the trade-off, and in general, converting cropland into natural grassland and evergreen trees performed relatively better in carbon sequestration and soil water maintenance; (2) in rainfall zones less than 550 mm, natural grassland exhibited higher advantages in increasing SOC stock but maintained a lower SWS depletion, while forest was a better choice for rainfall greater than 550 mm; and (3) with increasing restoration age, SOC stock and SWS depletion both increased significantly; nevertheless, natural grassland appeared to be sustainable and stable to achieve a win–win result. Moreover, with increasing age, an accumulation of 0.7 Mg ha−1 SOC stock in the upper 100 cm was associated with an approximately 5.14 mm SWS decrease in the 0–500 cm soil layers. Overall, this study provides practical insights for land and water managers on how to achieve win–win results for soil- and water-related ecosystem services during ecological restoration in water-limited regions.