Evenness drives consistent diversity effects in intensive grassland systems across 28 European sites

Abstract

Summary1 Ecological and agronomic research suggests that increased crop diversity in speciespoor intensive systems may improve their provision of ecosystem services. Such general predictions can have critical importance for worldwide food production and agricultural practice but are largely untested at higher levels of diversity. 2 We propose new methodology for the design and analysis of experiments to quantify diversity-function relationships. Our methodology can quantify the relative strength of inter-specific interactions that contribute to a functional response, and can disentangle the separate contributions of species richness and relative abundance. 3 Applying our methodology to data from a common experiment at 28 European sites, we show that the above-ground biomass of four-species mixtures (two legumes and two grasses) in intensive grassland systems was consistently greater than that expected from monoculture performance, even at high productivity levels. The magnitude of this effect generally resulted in transgressive overyielding. 4 A combined analysis of first-year results across sites showed that the additional performance of mixtures was driven by the number and strength of pairwise inter-specific interactions and the evenness of the community. In general, all pairwise interactions contributed equally to the additional performance of mixtures; the grass-grass and legume-legume interactions were as strong as those between grasses and legumes. 5 The combined analysis across geographical and temporal scales in our study provides a generality of interpretation of our results that would not have been possible from individual site analyses or experimentation at a single site. 6 Our four-species agricultural grassland communities have proved a simple yet relevant model system for experimentation and development of methodology in diversity-function research. Our study establishes that principles derived from biodiversity research in extensive, semi-natural grassland systems are applicable in intensively managed grasslands with agricultural plant species.

Integrated Analysis of Productivity and Biodiversity in a Southern Alberta Prairie

“…Recent studies have shown that both species richness and evenness have positive effects on the diversity-productivity relationship in ecosystems [59][60][61]. In accordance with another recent study [35], our measure of optical diversity showed a better correlation with the Shannon index than richness per se, suggesting that vegetation evenness (or heterogeneity) influences both optical diversity and the productivity patterns detected by NDVI.…”

Effect of four plant species on soil 15N-access and herbage yield in temporary agricultural grasslands

“…Increasing herbage yields with increasing plant species richness (positive plant diversity effects) were also shown in other studies on agricultural grassland mixtures (Frankow-Lindberg et al 2009;Kirwan et al 2007;Nyfeler et al 2009;Picasso et al 2008). The same was not the case for lucerne in pure stand, but growth conditions must have been optimal for lucerne, as herbage yields were high in both years and the proportion of lucerne in the mixture increased from the first to the second year.…”

“…Positive plant diversity-productivity relationships have been reported for experimental semi-natural grasslands (Cardinale et al 2006;Hector et al 1999;Tilman et al 1996) as well as temporary agricultural grasslands (Frankow-Lindberg et al 2009;Kirwan et al 2007;Nyfeler et al 2009;Picasso et al 2008). Generally, these relationships are explained, on the one hand, by niche differentiation and facilitation (Hector et al 2002;Tilman et al 2002) and, on the other hand, by greater probability of including a highly productive plant species in high diversity plots (Huston 1997).…”

An ecological economic assessment of risk-reducing effects of species diversity in managed grasslands

“…Tilman et al, 2006) and intensively managed grasslands across Europe (e.g. Kirwan et al, 2007), and thus applies to many different species compositions, environmental settings and management intensities. Increasing yields with increasing species diversity are typically explained by the niche complementarity concept (see section 2 for details).…”