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

Abstract

1. Forest ecosystem functioning generally benefits from higher tree species richness, but variation within richness levels is typically large. This is mostly due to the contrasting performances of communities with different compositions. Evidencebased understanding of composition effects on forest productivity, as well as on multiple other functions will enable forest managers to focus on the selection of species that maximize functioning, rather than on diversity per se.2. We used a dataset of 30 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 above-ground wood production (productivity) generally also fulfil the multiple other ecosystem functions (multifunctionality). Then, we quantified the species identity 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. Species identity and composition effects are essential to the development of high-performing production systems, for instance in forestry and agriculture. They therefore deserve great attention in the analysis and design of functional biodiversity studies if the aim is to inform ecosystem management. A management focus on tree productivity does not necessarily trade-off against other ecosystem functions; high productivity and multifunctionality can be combined with an informed selection of tree species and species combinations.

Transferring biodiversity-ecosystem function research to the management of ‘real-world’ ecosystems

“…An additional benefit of BEF experiments is that they often provide information on a wider range of ecosystem services than many agricultural experiments and agronomic analyses, which tend to focus on yield and its sustainability, e.g., weed control and nutrient cycling (Meyer et al, 2018). Mixtures that promote the supply of multiple ecosystem services simultaneously may therefore be identified from BEF studies (Baeten et al, 2019;Storkey et al, 2015). Further evidence of existing BEF transfer comes from grassland studies, which indicate that there are multiple benefits of diversifying agroecosystems in terms of grass yield and reduced weed abundance (Finn et al, 2013).…”

Above‐ and below‐ground biodiversity jointly regulate temperate forest multifunctionality along a local‐scale environmental gradient

“…soil macroscopic animals and microbial diversity such as bacteria, fungi and nematodes; Townshend, 1963;Wagg, Bender, Widmer, & Heijden, 2014). Existing studies have mainly focused on biodiversity within a single trophic group (Delgado-Baquerizo et al, 2016;Felipe-Lucia et al, 2018), neglecting the fact that ecosystem functioning depends strongly on complex interactions between trophic levels and between above-and below-ground biodiversity (Baeten et al, 2018;Schuldt et al, 2018;Soliveres et al, 2016). Further studies are needed to explore the relative effects of above-and below-ground biodiversity on forest multifunctionality (FM) while considering the direct and indirect effects of environmental conditions (see Figure 1a).…”

“…In addition, ecosystem multifunctionality may be driven by different individual functions that respond strongly to diversity or environmental conditions or by all functions increasing together (Zirbel, Grman, Bassett, & Brudvig, 2019). Thus, identifying how different ecosystem functions respond to biodiversity and environmental conditions, as well as their relative contributions to multifunctionality, is critical to formulating sustainable management and conservation policies (Baeten et al, 2018;Felipe-Lucia et al, 2018; van der Plas, 2019).…”

How do trees respond to species mixing in experimental compared to observational studies?

“…In theory, any positive effect of species diversity could stem from either positive interactions between the co-occurring species (complementarity effects, Loreau & Hector, 2001) or from the admixing of one or few exceptionally productive or dominating species (selection effects, Loreau & Hector, 2001). Depending on the forest ecosystem, species-specific growth responses to increasing tree diversity can be consistently positive (Chamagne et al, 2017;Liang et al, 2016) or variable, depending on the species and context (Baeten et al, 2019;Jucker, Bouriaud, Avacaritei, Dănilă, et al, 2014;Ratcliffe, Holzwarth, Nadrowski, Levick, & Wirth, 2015;del Río et al, 2017;Tobner et al, 2016). It is unclear to what extent these differences in species responses to tree diversity are caused by differences in species-specific characteristics (Fichtner et al, 2017;Williams, Paquette, Cavender-Bares, Messier, & Reich, 2017) or differences in study design.…”