Identifying the tree species compositions that maximize ecosystem functioning in European forests

Inglés. peer reviewed

Inglés. 1. Forest ecosystem functioning generally benefits from higher tree species richness, but within richness levels variation is typically large, mostly due to the contrasting performances of communities with different compositions. Evidence-based understanding of composition effects on forest productivity as well as on multiple other functions has large practical relevance, because forest managers are more likely to be concerned with the selection of species that maximize functioning rather than with diversity per se. 2. Here we used a dataset of thirty ecosystem functions measured in stands with different species richness and composition in six European forest types. First, we quantified whether the compositions that maximize annual aboveground wood production (productivity) generally also fulfill the multiple other ecosystem functions (multifunctionality). Then, we quantified the species identify effects and strength of interspecific interactions, to identify the “best” and “worst” species composition for multifunctionality. Finally, we evaluated the real-world frequency of occurrence of best and worst mixtures, using harmonized data from multiple national forest inventories. 3. The most productive tree species combinations also tended to express relatively high multifunctionality, although we found a relatively wide range of compositions with high or low average multifunctionality for the same level of productivity. Monocultures were distributed among the highest as well as the lowest performing compositions. The variation in functioning between compositions was generally driven by differences in the performance of the component species and, to a lesser extent, by particular interspecific interactions. Finally, we found that the most frequent species compositions in inventory data were monospecific stands and that the most common compositions showed below-average multifunctionality and productivity. 4. Synthesis and applications. While a management focus on productivity does not necessarily trade-off against other ecosystem functions, it matters considerably which particular tree species and combinations are promoted. These identity and composition effects are essential in thecontext of developing high-performing production systems, for instance in forestry and agriculture, and deserve much more attention in the analysis and design of functional biodiversity studies if the aim is to inform ecosystem management.