On the relative importance of land use, landscape characteristics, bird and plant assemblages as drivers of Mediterranean ecosystem functioning

Context Mediterranean landscapes are undergoing severe transformations (land-use change and homogenization) that threatens biodiversity and the services these ecosystems provide. These effects can differ amongst biodiversity facets (plants vs. birds, taxonomic vs. functional) and ecosystem functions (e.g., seed dispersal, forest regeneration, pest control), although these are still poorly understood in Mediterranean landscapes. Objectives Our study aims at understanding how Mediterranean landscape characteristics and land use (tree croplands, shrublands and pine, oak and mixed forest) affect the diversity of birds and plants, and how these changes in biodiversity could affect ecosystem functioning. Methods In 2020–2021, we sampled 49 (5 × 5 m) plots in South-eastern Spain and from five different land uses: tree croplands, shrublands, and pine, oak and mixed forests. We measured land use, habitat diversity and size, together with birds and plant diversity. We assessed both direct and indirect (via bird and plant diversity) effects of landscape characteristics on 6 different ecosystem functions related to forest regeneration, predation, herbivory or aboveground biomass, which imply interactions between birds, plants and their environment. Results Plant communities responded mainly to local features (land use), whereas birds did so to habitat size and landscape diversity (within 500 m radius). Seed and caterpillar predation were more affected by bird’s diversity, whereas regeneration capacity of woody species was driven by both plants and birds. Land use was amongst the most important drivers of all measured functions, with generally higher functioning levels in oak and mixed forests than in the rest of land uses. Conclusions Our results emphasize the complementary information obtained when considering multiple biodiversity facets in studying the consequences of landscape transformation. We also show that these multiple biodiversity changes can be as important as those of land-use or landscape characteristics for ecosystem functioning.