Partitioning the effects of plant diversity on ecosystem functions at different trophic levels

Abstract

Biodiversity effects on ecosystem functioning can be partitioned into complementarity effects, driven by many species, and selection effects, driven by few. Selection effects occur through interspecific abundance shifts (dominance) and intraspecific shifts in functioning. Complementarity and selection effects are often calculated for biomass, but very rarely for secondary productivity, that is, energy transfer to higher trophic levels. We calculated diversity effects for three functions: aboveground biomass, insect herbivory and pathogen infection, the latter two as proxies for energy transfer to higher trophic levels, in a grassland experiment (PaNDiv) manipulating species richness, functional composition, nitrogen enrichment, and fungicide treatment. Complementarity effects were, on average, positive and selection effects negative for biomass production and pathogen infection and multiple species contributed to diversity effects in mixtures. Diversity effects were, on average, less pronounced for herbivory. Diversity effects for the three functions were not correlated, because different species drove the different effects. Benefits (and costs) from growing in diverse communities, be it reduced herbivore or pathogen damage or increased productivity either due to abundance increases or increased productivity per area were distributed across different plant species, leading to highly variable contributions of single species to effects of diversity on different functions. These results show that different underlying ecological mechanisms can result in similar overall diversity effects across functions.

Nitrogen enrichment and foliar fungal pathogens affect the mechanisms of multispecies plant coexistence

“…For instance, T. officinale could coexist in most combinations under N addition because its growth rate was reduced in comparison with control conditions, as previously observed (Murray et al ., 1983). Also, C. jacea could not coexist under pathogen suppression perhaps because it was one of the species that most strongly increased its pathogen infection in mixed communities, presumably due to spillovers from other species (Cappelli et al ., 2022). Finally, D. glomerata under N addition and P. media under pathogen suppression did not coexist in species pairs but could coexist in multispecies assemblages, indicating that the compositional consequences of N addition, pathogen suppression and their combination are also dependent on the number of interacting species.…”

Nitrogen availability and plant functional composition modify biodiversity-multifunctionality relationships

“…Instead, species richness increased belowground biomass and carbon storage regardless of community SLA, and phosphatase activity peaked in plots dominated by slow species, regardless of their richness. Diversity therefore did increase several individual functions within slow species communities, presumably because the slow species were complementary in their effects on these individual functions (Cappelli et al, 2022), but this complementarity was not realised when combining multiple functions.…”

Using root economics traits to predict biotic plant soil-feedbacks

“…In addition, functional traits can be linked to biodiversity effects on production (selection and complementarity; Loreau and Hector 2001; see eg. Jing et al 2015;Cadotte 2017;Bakker et al 2019;Cappelli et al 2022). Linking root traits to biodiversity effects could be a promising way to test mechanisms by which root trait functional diversity might enhance plant productivity and ecosystem functioning.…”