Minimising the relative regret of future forest landscape compositions: The role of close-to-nature stand types

Increasingly uncertain decision outcomes prevail in forest management and hamper choosing a single optimal management alternative. Confronting all management alternatives with multiple future scenarios and selecting an alternative minimising the regret under the worst scenario may provide suitable guidance under such uncertainty. Here, we search for future forested landscape compositions using regret minimisation for different objectives. We consider even-aged and uneven-aged stand types (called close-to-nature stand types) as management alternatives. Close-to-nature forest stand types supported the minimisation of regret for all objectives (represented by financial return, volume increment, C-storage, and two biodiversity indicators). However, close-to-nature stand types covered 18 % to 43 % of the future forest landscape in our study, which shows that even-aged stands are also necessary. For example, supporting biodiversity or multiple objectives simultaneously required large proportions of light-demanding and climate-change-tolerant Oak stands (even aged). Such Oak stands are difficult to achieve under shady conditions with limited canopy openings, which is typical for uneven-aged systems. Building on robust Pareto frontiers, we show a substantial trade-off between supporting biodiversity and maximising financial return but only a moderate trade-off between supporting biodiversity and maximising the C storage in a forest landscape. We suggest that such landscape-level trade-offs be quantified and discussed more intensively.