Influence of management and stand composition on ecosystem multifunctionality of Mediterranean tree forests

Key message: The multiple functions of Mediterranean forest ecosystems primarily decrease with management operations, and secondarily with tree composition. This finding emphasizes the importance of a suitable management for maintaining ecosystem functioning in Mediterranean forests. Abstract: In semi-arid ecosystems, forests are critical sites for supporting multifunctionality, which are endangered by multiple environmental stresses. In this regard, understanding how ecosystem multifunctionality (EMF) develops in semi-arid forests is important to set up actions preserving these delicate environments. Changes in species composition and management operations can have heavy effects on the Mediterranean forest ecosystem. To better understand the influence of these drivers on EMF of Mediterranean forests, this study compares ecosystem structure, properties and functions as well as the resulting EMF in four types of forests in Central-Eastern Spain: (1) a pure and unmanaged stand of Spanish black pine, assumed as control; (2) a pure, but managed stand of Spanish black pine; (3) two mixed and unmanaged stands of Spanish black pine and (3.a) Spanish juniper and (3.b) holm oak. Regarding the ecosystem structure, both forest management and stand composition altered plant diversity, but not soil covers (except for vegetation). About the ecosystem properties, soil characteristics significantly changed between pairs of stands (especially texture, pH and bulk density). Concerning the ecosystem functions, forest stand structure was a significant driver of waste decomposition, but not of wood production, while its effect on nutrient cycling, belowground carbon stocks and water cycle was different according to the specific tree species. The impacts of forest management on the ecosystem functions were in general significant compared to the unmanaged stand in terms of wood production, belowground carbon stocks and nutrient cycling, but not of water cycle and waste decomposition. Overall, this study demonstrates that the average EMF is primarily affected by forest management (with a decrease in EMF in managed stands compared to the unmanaged forest), and by stand composition only in the case of one mixed stand. As such, the forest management actions must be carefully adopted, to avoid EMF degradation.