Management legacies and forest attributes shape soil organic carbon dynamics in Quercus ilex open woodlands

Résumé fourni par la source

Mediterranean open woodlands are increasingly affected by management change and climatic drying, yet the long-term consequences for soil carbon storage and stand condition remain poorly understood. We reconstructed soil organic carbon (SOC) trajectories in Iberian Quercus ilex dehesas by integrating CHELSA climate data, Spanish National Forest Inventory vegetation data, and regional soil observations from a European forest-monitoring network within the RothC model. Simulations covered the upper 20 cm soil layer from 1991 to 2017 and interpreted as model-based reconstructions of relative SOC trajectories. We compared three management trajectories inferred from shrub-cover dynamics: traditional management (TM), land-use abandonment (LA) and shrub clearance (SC). RothC simulations and additive mixed models indicated divergent modelled SOC trajectories associated with contrasting management legacies. LA plots showed the largest net SOC gain (5.12 Mg ha⁻¹) but also the highest tree mortality and shrub encroachment; SC plots showed net SOC losses (-0.43 Mg ha⁻¹) despite improved stand structure; and TM plots showed small net SOC gains (1.93 Mg ha⁻¹). These results suggest a management trade-off: pathways associated with higher modelled SOC accumulation may coincide with structural and demographic degradation that could compromise open-woodland persistence. Within TM plots, mixed‑effects models indicated that adult tree density was positively associated with SOC balance, whereas mortality became negatively associated during the later period; regeneration and shrub cover also showed positive later-period associations. We conclude that adaptive traditional management supporting tree continuity, regeneration, and controlled understory retention may contribute to maintaining both SOC stocks and dehesa functioning under increasing climatic stress.