Climate-driven soil dynamics over 30 years: insights from biological indicators across mediterranean shrubland recovery following agricultural abandonment

Soil biota plays a key role in pedogenesis, influencing nutrient cycling, organic matter transformation, and soil structure, while its composition depends on edaphic properties and pedological origin. In Mediterranean ecosystems, semi-arid conditions and historical land use have altered soil and vegetation dynamics, making natural recovery after land abandonment slow and uncertain. We assessed soil quality more than three decades after agricultural and pastoral abandonment on Pianosa Island a very representative territory of Mediterranean environment, characterized to be a limestone plateau of about 10km2, approximately 20-25 m above sea level. The island has been a penal agricultural colony for more than one century, intensively exploiting almost the entire surface. The agricultural fields have been abandoned at the beginning of the 90's and the natural vegetation is now expanding, with different degree along the island. For its peculiar history and nature, Pianosa represents an extrapordinary on-field natural laboratory. An integrated approach was used to assess soil quality, combining vegetation surveys and chemical, physical, and biological soil analyses. Five environmental groups were identified, reflecting different regeneration stages: ex-managed areas with low Mediterranean shrub recovery degree, consistent with a higher contribution of pioneer and sub-mature shrub species; ex-managed areas with high Mediterranean shrub recovery, with a greater presence of mature shrub species and a more developed shrub structure; Mediterranean shrublands; coniferous forests; and coniferous forests largely colonized by Mediterranean shrubs. Results indicate that, even without human disturbance, recovery of soil biological attributes is extremely slow. Intrinsic soil properties and historical vegetation legacies strongly influence biotic reassembly and ecosystem functioning. These findings underscore the need to integrate pedological constraints and biological indicators in restoration strategies to sustain ecosystem services in Mediterranean landscapes.