Nitrogen availability and plant functional composition modify biodiversity-multifunctionality relationships

Abstract

The ability of an ecosystem to deliver multiple functions at high levels (multifunctionality) typically increases with biodiversity but there is substantial variation in the strength and direction of biodiversity effects, suggesting context-dependency. However, the drivers of this context dependency have not been identified and understood in comparative meta-analyses or experimental studies. To determine how different factors modulate the effect of diversity on multifunctionality, we conducted a large grassland experiment with 216 communities, crossing a manipulation of plant species richness (1-20 species) with manipulations of resource availability (nitrogen enrichment), plant functional composition (gradient in mean specific leaf area [SLA] to manipulate abundances of fast vs. slow species), plant functional diversity (variance in SLA) and enemy abundance (fungal pathogen removal). We measured ten functions, above and belowground, related to productivity, nutrient cycling and energy transfer between trophic levels, and calculated multifunctionality. Plant species richness and functional diversity both increased multifunctionality, but their effects were context dependent. Species richness increased multifunctionality, but only when communities were assembled with fast growing (high SLA) species. This was because slow species were more redundant in their functional effects, whereas fast species tended to promote different functions. Functional diversity also increased multifunctionality but this effect was dampened by nitrogen enrichment, however, unfertilised, functionally diverse communities still delivered more functions than low diversity, fertilised communities. Our study suggests that a shift towards exploitative communities will not only alter ecosystem functioning but also the strength of biodiversity-functioning relationships, which highlights the potentially complex effects of global change on multifunctionality.

Multiple dimensions of biodiversity mediate effects of temperature on invertebrate herbivory in a montane grassland

“…For example, along this same elevational gradient, low elevation, warmer sites, tended to be dominated by species with fast‐paced life history strategies, while high elevation, cooler sites were dominated by species with slow‐paced life history strategies, with impacts on plant disease severity (Halliday et al 2021). Plant life history strategies can be important drivers of invertebrate herbivory (Coley et al 1985, Herms and Mattson 1992, Stamp 2003, Loranger et al 2012, Züst and Agrawal 2017), yet understanding how plant life‐history and plant diversity interact to influence herbivory remains a frontier in ecology (Cappelli et al 2022, Pichon et al 2022).…”

Plant attributes interact with fungal pathogens and nitrogen addition to drive soil enzymatic activities and their temporal variation

“…To maintain species compositions, the plots were weeded three times a year in April, July and September, and mown twice annually in June and August, which corresponds to relatively extensive management in lowland grasslands. Further details about the site characteristics and experimental setup of the PaNDiv Experiment are shown in Figure S1 and in (Pichon, Cappelli, Soliveres, Hölzel, et al, 2020; Pichon, Cappelli, Soliveres, Mannall, et al, 2020). The field work did not require any special permits.…”

“…The study was carried out in the PaNDiV grassland experiment (47°1′18.3″N, 7°27′1.3″ E) in Münchenbuchsee, near Bern, Switzerland (Pichon, Cappelli, Soliveres, Hölzel, et al, 2020; Pichon, Cappelli, Soliveres, Mannall, et al, 2020). The grassland was previously extensively managed for sheep grazing and forage production (Cappelli et al, 2020).…”

“…We then calculated a CWM SLA value for each plot by multiplying each species' relative abundance by the mean SLA value of the species in monoculture, in the respective treatment, to account for intraspecific trait variation due to the N and fungicide addition. To obtain a measure of functional diversity, we calculated the mean pairwise distance (MPD) in SLA between species within communities in each plot (Pichon, Cappelli, Soliveres, Hölzel, et al, 2020; Pichon, Cappelli, Soliveres, Mannall, et al, 2020). We used unweighted MPD, based on the presence/ absence of fast and slow species in each plot, as this is least correlated with CWM SLA and the other treatments.…”

Geologically younger ecosystems are more dependent on soil biodiversity for supporting function

“…3). We hypothesized that soil age, together with other important factors affecting pedogenesis such as climatic and biotic (including plant and microbial) attributes, may influence BEF relationships directly or indirectly by influencing edaphic variables and microbial biomass production 7,25,46 . The chi-squared test (χ 2 , the model has a good fit when χ 2 was low and the P-value > 0.05) and the root-mean-square error of approximation (RSMEA, the model has a good fit when 0 ≤ RMSEA ≤ 0.05) were conducted to test the overall goodness of SEM 47,48 .…”