Plant and soil biodiversity is essential for supporting highly multifunctional forests during Mediterranean rewilding

The multidimensional dynamics of biodiversity and ecosystem function during the rewilding of Mediterranean forests remain poorly understood, limiting our capacity to predict how future restoration efforts may help mitigating climate change. Here, we investigated the changes in multiple dimensions of biodiversity and ecosystem services in a 120-year forest succession after harvest to identify potential trade-offs in multiple dimensions of ecosystem function, and further assess the link between above and belowground biodiversity and function. We found a positive influence of successional age on multiple dimensions of biodiversity and function, but also some important trade-offs. Two ecosystem axes of function explained nearly 75.4% functional variation during ecosystem rewilding. However, while the first axis increased with successional age promoting plant productivity and element stocks, the second axis followed a hump-shaped relationship with age supporting important reductions in nutrient availability and pathogen control in old forests. Our study further revealed that a significant positive relationship between plant and soil biodiversity with multiple elements of multifunctionality as forests develop. Moreover, the influence of plant and soil biodiversity were especially important to support a high number of function working at high levels of functioning. Our work provides new insights on the patterns and functional trade-offs in the multidimensional rewilding of forests, and further highlight the importance of biodiversity for long-term Mediterranean rewilding.