Neighbourhood interactions drive overyielding in mixed-species tree communities

Abstract

Theory suggests that plant interactions at the neighbourhood scale play a fundamental role in regulating biodiversity–productivity relationships (BPRs) in tree communities. However, empirical evidence of this prediction is rare, as little is known about how neighbourhood interactions scale up to influence community BPRs. Here, using a biodiversity–ecosystem functioning experiment, we provide insights into processes underlying BPRs by demonstrating that diversity-mediated interactions among local neighbours are a strong regulator of productivity in species mixtures. Our results show that local neighbourhood interactions explain over half of the variation in observed community productivity along a diversity gradient. Overall, individual tree growth increased with neighbourhood species richness, leading to a positive BPR at the community scale. The importance of local-scale neighbourhood effects for regulating community productivity, however, distinctly increased with increasing community species richness. Preserving tree species diversity at the local neighbourhood scale, thus seems to be a promising way for promoting forest productivity.

Neighbour species richness and local structural variability modulate aboveground allocation patterns and crown morphology of individual trees

“…At all levels we observed significant neighbourhood diversity effects, which supported our third hypothesis. For the BEF‐China experiment it has been found that tree species richness increased productivity both at the individual‐tree (Fichtner et al , ) and at the stand‐level (Huang et al ). Our analysis indicates that both main aboveground woody compartments, i.e.…”

Diversity and forest productivity in a changing climate

“…() found that focal trees exposed to intraspecific competition grew less well than trees in interspecific surroundings. These studies indicate that downscaling to the individual tree level may elucidate the interactions underlying the diversity–productivity relationship at the stand level (Chen et al ., ; Riofrío et al ., ; Fichtner et al ., ). However, this approach requires equal neighbourhood density, and contrasting results have also been reported.…”

Tree performance in a biodiversity enrichment experiment in an oil palm landscape

“…Plot‐level analyses are considered useful to assess overyielding (and underyielding), a widely used concept in BEF research to compare productivity across stands (Ammer, ). However, local neighbourhoods predominantly drive the response of tree productivity to diversity and can inform about the BEF relationship at plot level (Chen et al, ; Fichtner et al, ; Potvin & Dutilleul, ). Here, we suggest that evaluating the effect of tree diversity over time, accounting for changing competitive pressures in local neighbourhoods, is needed for a comprehensive understanding of BEF relationships in tree diversity experiments.…”

“…In contrast to grassland experiments, however, tree‐based BEF‐experiments are still scarce, particularly in the tropics (Paquette et al, ). Results from these tree diversity experiments suggest that tree diversity often positively affects tree growth (Fichtner et al, ; Grossman et al, ; Huang et al, ; Paquette & Messier, ; Potvin & Gotelli, ; Van der Peer, Verheyen, Ponette, Setiawan, & Muys, ), and temporal stability of primary productivity (Hutchison, Gravel, Guichard, & Potvin, ; Morin, Fahse, Mazancourt, Scherer‐Lorenzen, & Bugmann, ). Such BEF‐effects have been linked to mechanisms such as niche differentiation, increased resource use efficiency due to interactions between species (“complementarity effects”) or selection and dominance of species with particular traits in mixtures (“selection effects”; Loreau & Hector, ).…”