Understorey biodiversity supports multiple ecosystem services in mature Mediterranean forests

Overstorey biodiversity is known to drive multiple ecosystem functions in mature forests. However, the role of understorey biodiversity in regulating the soil microbiome and ecosystem multiservices of these ecosystems is virtually unknown. Here, we collected vegetation and soil data from mature plantation Mediterranean pine forests (100 years old) with different combinations of tree and understorey plant species to explore the contribution of overstorey and understorey biodiversity for explaining soil microbiomes and ecosystem multiservices. We found that while overstorey diversity is important for supporting soil-borne pathogen control, forest understorey biodiversity is critical for explaining soil nutrient availability, tree production, and soil-plant mutualistic relationships. Our results highlight the importance of understorey biodiversity for maintaining ecosystem multiservices in mature forests, which should be considered in forest management programs.