Nitrogen addition does not reduce the role of spatial asynchrony in stabilising grassland communities

Abstract

While nitrogen (N) amendment is known to affect the stability of ecological communities, whether this effect is scale-dependent remains an open question. By conducting a field experiment in a temperate grassland, we found that both plant richness and temporal stability of community biomass increased with spatial scale, but N enrichment reduced richness and stability at the two scales considered. Reduced local-scale stability under N enrichment arose from N-induced reduction in population stability, which was partly attributable to the decline in local species richness, as well as reduction in asynchronous local population dynamics across species. Importantly, N enrichment did not alter spatial asynchrony among local communities, which provided similar spatial insurance effects at the larger scale, regardless of N enrichment levels. These results suggest that spatial variability among local communities, in addition to local diversity, may help stabilise ecosystems at larger spatial scales even in the face of anthropogenic environmental changes.

General destabilizing effects of eutrophication on grassland productivity at multiple spatial scales

“…6 ). Our results extend previous evidence of the negative impact of fertilization on the diversity–stability relationship obtained within local plots and over shorter experimental periods 4 , 6 , 26 . Importantly, they show that these negative effects propagate from within to among communities.…”

“…Analyses of variance revealed the negative effects of nutrient inputs on biodiversity and stability at the two scales investigated, consistent with recent findings from a single site 26 . Fertilization consistently reduced species richness, alpha, and gamma stability, but had no effect on beta diversity (Supplementary Fig.…”

“…To our knowledge, only one recent study has assessed the effect of nutrient enrichment on stability within and among interconnected communities in a temperate grassland 26 . By adding different nitrogen treatments to communities in ten blocks spread out within a single site, that study found that 5 years of chronic nitrogen addition reduced alpha stability through a decline in species asynchrony, but had no effect on spatial asynchrony.…”

Local species diversity, β-diversity and climate influence the regional stability of bird biomass across North America

“…Our study provides some of the first evidence to suggest that at macroscales, biomass is stabilized more by spatial variation in biomass fluctuations and species composition than average local stability or species diversity. Moreover, our results suggest recent theory on scaling biodiversity-stability relationships [25,29] (which has mostly been tested with sessile organisms like plants [26,46,47,71]) can be generalized to more mobile consumers like birds.…”

“…However, most prior tests of the importance of β-diversity and spatial asynchrony come from studies of plant communities at relatively small scalesmetacommunities less than 1 ha in size (median 0.5 ha) and/ or single grasslands [26,46,47]-which may not contain the abiotic heterogeneity or variation in species composition necessary to drive spatial asynchrony. Consistent with these expectations, these studies typically found local stability was more important than plant β-diversity or spatial asynchrony for stabilizing biomass at larger scales [26,47]. The lack of studies across heterogeneous ecosystems or outside of plant communities limits our understanding of how and why biodiversity contributes to ecosystem stability at large, regional scales.…”