Résumé
The multifunctionality of Central European mountain forests has long been acknowledged, as they host numerous emblematic species, supply timber, provide important protection against natural hazards as well as aesthetic and recreational functions. These forests have a long tradition of management under the selection system, which is considered to be favorable to this multifunctionality. However, the explicit consideration of ecosystem service (ES) provision in management planning is a recent issue that requires a better understanding of their response to silvicultural practices. Decision support systems are thus of great interest, but they often rely on the comparison of contrasted management practices and only rarely on adjustments within a given silvicultural system. Our objectives were therefore (i) to study the impacts of variations within uneven-aged management practices on timber production, biodiversity conservation and protection against natural hazards; and (ii) to detect and study trade-offs between these ES. We conducted a simulation study coupling an uneven-aged management algorithm with Samsara2, an individual-based, spatially explicit forest model designed for uneven-aged spruce-fir mountain forests. Sensitivity analysis techniques enabled influential silvicultural factors to be detected, like gap size, harvesting diameter, harvesting and thinning intensity. A meta-modelling approach enabled the response surfaces of the different ES indicators to be established and analyzed, revealing interactions effects and/or potential compensating effects between some factors. This especially highlighted the importance of large tree retention to compensate for the negative impact of harvesting intensity on tree size diversity. Trade-offs between production, protection and biodiversity indicators were then identified and studied using Pareto frontier techniques, and efficient management prescriptions resulting from the simulation study were discussed with forest managers and compared to current practices.