Trade-off between soil carbon and water following revegetation across climatic gradients on the Loess Plateau

Abstract

Vegetation restoration effectively combats land degradation and mitigates climate change by enhancing soil carbon sequestration. However, it often depletes soil water storage (SWS), potentially threatening ecosystem sustainability in arid and semi-arid regions. Although evidence shows that climate and vegetation type profoundly shape soil carbon–water interactions, the underlying mechanisms remain poorly understood. This study analyzed data from 174 observations to assess soil organic carbon storage (SOCS) and SWS (0–500 cm), their trade-offs, and the coupling coordination level (0–100 cm) across vegetation types, including grassland, shrubland, and forestland (Robinia pseudoacacia and economic forests) on the Loess Plateau. The findings revealed an optimal trade-off between SOCS and SWS in forestland, with economic forests slightly outperforming Robinia pseudoacacia. Grassland and shrubland exhibited less favorable outcomes. Within the 0–500 cm soil layers, economic forests demonstrated the highest levels of both SOCS (20.20 kg m⁻²) and SWS (857.95 mm), whereas Robinia pseudoacacia had higher SOCS (19.36 kg m⁻²) but lower SWS (574.64 mm). Grassland had lower SOCS (13.00 kg m⁻²) and higher SWS (634.65 mm), while shrubland had the lowest levels of both SOCS (12.55 kg m⁻²) and SWS (480.17 mm). The effect of precipitation and temperature on the carbon–water relationship was non-linear. Based on these results, the revegetation recommendations included grassland for areas with a mean annual precipitation (MAP) > 450 mm, and mean annual temperature (MAT) < 9 °C; shrubland for MAP between 450 and 500 mm, and MAT < 9 °C; Robinia pseudoacacia for MAP > 530 mm, and MAT between 9 °C and 10 °C; and economic forests for MAP between 450 and 530 mm, and MAT > 10 °C. These findings underscore the pivotal role of vegetation type and climate in regulating soil carbon–water dynamics and help identify optimal climatic zones for different vegetation types on the Loess Plateau.