Soil carbon-water trade-offs during vegetation restoration on the Loess Plateau: a meta-analysis.

Vegetation restoration can enhance soil carbon sequestration but may deplete soil water in drylands. We synthesized 1045 soil organic carbon (SOC) and 875 soil moisture content (SMC) observations from 77 publications on cropland restoration across the Loess Plateau to identify where and when carbon gains coincide with water costs. Overall, restoration increased SOC by 39.2% but reduced SMC by 10.7%. Woody restoration produced larger carbon gains but greater soil-water losses than meadow restoration. SOC accumulation was concentrated in surface soils, whereas marked SMC depletion occurred below 300 cm under forests and shrubs. The imbalance was most evident during the 10-25 yr restoration stage. Nonlinear precipitation responses further showed that greater rainfall did not consistently alleviate soil-water costs. Species-level responses ranged from high-carbon-high-water-cost patterns to more balanced SOC-SMC responses. These findings identify the vertical, temporal, and biological contexts of restoration-induced carbon-water imbalance and provide a risk-based basis for carbon-water-balanced restoration.