Management of marginal landscapes in the Mediterranean mountains: Driving soil regulatory functions towards Global Change adaptation.

Mediterranean mountain regions provide essential ecosystem services and resources to surrounding urban areas. Since the mid-20th century, however, rural depopulation has led to widespread land abandonment, triggering natural revegetation and consequent shrub encroachment. These changes have been associated with increased wildfire risk, reduced agro-pastoral resources, and altered hydrological functioning. Soil, a non-renewable resource on human timescales, plays a key role in ecosystem resilience due to its influence on biogeochemical cycles and carbon accumulation, making it a potential tool in Climate Change adaptation strategies.

This study, grounded in the MANMOUNT project (PID2019-105983RB-I00) investigates post-abandonment land management strategies in marginal Mediterranean mountain areas, focusing on their effects on soil quality and soil organic carbon (SOC) storage. The Leza Valley (Iberian System, Spain) was selected as the study area due to its representativeness of the historical and ecological context of Mediterranean mountains. Three management strategies were evaluated: passive management through secondary succession; forest management through conifer afforestation and dehesa systems; and shrub clearing to establish pastures for extensive grazing. Analyses considered soil environment (acid or alkaline), soil depth (0–40 cm), time since management implementation, and the presence of active management practices (e.g., thinning, selective cutting).

A total of 453 soil composite samples were collected and analysed to assess physicochemical properties and SOC stocks. Carbon stabilization mechanisms were examined using aggregate stability tests and fractionation techniques. Future SOC dynamics were projected under different Climate Change scenarios using the CarboSOIL predictive model, while integrated soil–water balance was evaluated with the RHESSys model.

Results revealed significant effects of post-abandonment management on soil quality and SOC storage. All management strategies increased carbon stocks compared to the initial unmanaged shrubland. Forest systems accumulated higher total SOC, whereas pasture systems promoted greater mineral-associated carbon, indicating enhanced long-term stability. Soil environment was a major driver of SOC responses, with marked differences between acid and alkaline soils. Model projections highlight the importance of sustained active management to maintain soil functions in abandoned areas under future climatic conditions.

These findings provide valuable insights for land managers and policymakers, underlining the potential of post-abandonment management in marginal Mediterranean mountain landscapes as an important tool for Climate Change adaptation. The promotion of mosaic landscapes is proposed as an effective strategy to achieve both ecological resilience and socio-economic sustainability.

Acknowledgement: This research project was supported by the MANMOUNT (PID2019-105983RB-100/AEI/ 10.13039/501100011033) project funded by the MICINN-FEDER, and the SOLPYR (POCTEFA 2021-2027 (EFA045/01)) project funded by Interreg Poctefa and European Union.

Keywords: Mediterranean mountains; carbon sequestration; natural revegetation; extensive grazing; forest practices.