Effect of forest management on the ecosystem services supply and multifunctionality in the Urdaibai Biosphere Reserve

• Unmanaged forests and abandoned pines show higher ES supply than managed stands. • Soil pH, slope, and vertical heterogeneity drive ES supply and multifunctionality. • Abandoned pine stands regenerate naturally, providing ES like native forests. • Adopting ‘closer-to-nature’ forestry may enhance ES supply and multifunctionality. Forest ecosystems provide a wide range of ecosystem services (ES) that are essential for human well-being. Nevertheless, conventional forest management practices that prioritise timber production often reduce the capacity of forests to provide a balanced set of other ES, thereby diminishing their overall multifunctionality. The aim of this study is to develop a field-based multi-indicator methodological approach to assess how different forest management types influence the multifunctionality value based on the supply of thirteen ES (two provisioning, nine regulating and two cultural), and to identify the forest attributes (location, structure and maturity, and soil properties) that influence the provision of each ES. The research was conducted in the Urdaibai Biosphere Reserve, a relevant protected area of the Basque Country (Spain). The forest management types selected for the study were as follows: i) No managed native forests, ii) Abandoned pine plantations, iii) Pine managed plantations, and iv) Eucalyptus managed plantations, with 10 stands sampled for each management type. The findings indicated that No managed and Abandoned exhibited higher multifunctionality value and greater values in regulating and cultural ES in comparison to managed plantations, which supplied higher timber provision, yet exhibited suboptimal performance in other ES. The application of generalised linear mixed models has revealed a positive correlation between forest attributes, including soil pH and vertical heterogeneity, and the provision of multiple ES. However, it has also been observed that slope has a negative effect on certain regulating ES. These findings underscore the significance of forest management practices that preserve both the structural complexity of the forest and landscape, whilst simultaneously enhancing soil conditions to ensure multifunctionality. Furthermore, abandoned pine plantations have the potential to demonstrate ecological restoration, thereby supporting natural regeneration and improving the delivery of regulating and cultural ES.