Multiple facets of diversity effects on plant productivity: Species richness, functional diversity, species identity and intraspecific competition

Abstract

221. Deciphering the mechanisms that drive variation in biomass production across plant 23 communities of contrasting species composition and diversity is a main challenge of 24 biodiversity-ecosystem functioning research. Niche complementarity and selection effect have 25 been widely investigated to address biodiversity-productivity relationships. However, the 26 overlooking of the specific role played by key species have limited so far our capacity to 27 comprehensively assess the relative importance of other potential drivers of biodiversity effects. 28 2. Here, we conducted a grassland diversity-productivity experiment to test how four potential 29 facets of biodiversity effects, namely species richness, functional diversity, species identity and 30 the relaxation of intraspecific competition, account for variations in above and root biomass 31 production. 32 3. We grew six plant species in monoculture, as well as in every combinations of two, three and 33 six species. Plant density was kept constant across the richness gradient but we additionally 34 grew each species in half-density monoculture to estimate the strength of intraspecific 35 competition for each studied species. We characterized eight functional traits, including root 36 traits, related to nutrient and light acquisition and computed both the functional dissimilarity 37 and the community weighted mean (CWM) of each trait. We further partitioned aboveground 38 biodiversity effect into complementarity and selection effects. 39 4. We observed strong positive biodiversity effects on both aboveground and root biomass as 40 well as strong positive complementarity effect. These arose largely from the presence of a 41 particular species (Plantago lanceolata) and from CWM trait values more than from a higher 42 functional dissimilarity in plant mixtures. P. lanceolata displayed the highest intraspecific 43 competition, which was strongly relaxed in species mixtures. By contrast, the presence of 44 Sanguisorba minor negatively affected the productivity of plant mixtures, this species suffering 45 more from interspecific than intraspecific competition. 46 5. This study provides strong evidences that the search for key species is critical to understand 47 the role of species diversity on ecosystem functioning and demonstrates the major role that the 48 balance between intraspecific and interspecific competition plays in biodiversity-ecosystem 49 functioning relationships. Developing more integrative approaches in community and 50 ecosystem ecology can offer opportunities to better understand the role that species diversity 51 plays on ecosystem functioning. 52 53 Key words: biodiversity-ecosystem functioning, complementarity effect, functional trait, 54 functional distinctiveness, niche difference, roots, selection effect, species coexistence 55 56 57 58 59 60 61 62 63 64 65 Because ecological niches are theoretically linked to a suite of functional traits (Violle 91 & Jiang 2009), functional traits appear to be a promising tool for understanding diversity...

Bioactive properties of Sanguisorba minor L. cultivated in central Greece under different fertilization regimes

“…In a recent study, Karkanis et al (2019) reported that the type of growth substrate (different ratios of peat and perlite) had a significant effect on leaves and stems biomass of S. minor plants with the highest values being recorded for plants grown in sole peat substrate in comparison to plants grown in peat and perlite mixtures. Moreover, considering that the existing reports refer to genetic material from wild ecotypes with great diversity among them, the effect of genotype on agronomic performance has to be considered since complementarity and intra-or inter-specific competition in diversified wild ecosystems may affect plant productivity and selection process in natural environments (Mahaut, Fort, Violle, & Freschet, 2019).…”

Intraspecific trait changes have large impacts on community functional composition but do not affect ecosystem function

“…These leaf economics spectrum traits predict responses to soil fertility, with increases in mean SLA and decreases in mean LDMC of communities in high nitrogen conditions (Lavorel & Grigulis, 2012;Allan et al, 2015). Leaf economics spectrum traits also predict effects on a number of ecosystem functions, as slow growing communities (with low SLA and high LDMC) typically produce less aboveground biomass and have slow biogeochemical cycling, but may allocate more resources belowground (see Freschet, Swart, & Cornelissen, 2015;Mahaut, Fort, Violle, & Freschet, 2019). Understanding the ways in which community trait values change in response to the environment and affect ecosystem functioning is critical to a mechanistic understanding of global change effects on plant communities and their functioning.…”

Effects of functional traits of perennial ryegrass cultivars on forage quality in mixtures and pure stands

“…Cultivar and/or species mixtures optimized with respect to functional trait diversity have been discussed recently as being highly important for securing grassland productivity (Mahaut et al ., 2019; Lowry et al ., 2020). One principal question of the current study was whether cultivars of perennial ryegrass representing important functional traits affect forage quality in (i) pure stands and (ii) in mixtures with white clover or white clover and forbs.…”