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

Citation

Mahaut, Lucie; Fort, Florian; Cyrille, Violle; Freschet, Grégoire T. (2019), Data from: Multiple facets of diversity effects on plant productivity: species richness, functional diversity, species identity and intraspecific competition, Dryad, Dataset, https://doi.org/10.5061/dryad.1jwstqjqh

Abstract

1. Deciphering the mechanisms that drive variation in biomass production across plant communities of contrasting species composition and diversity is a main challenge of biodiversity-ecosystem functioning research. Niche complementarity and selection effect have been widely investigated to address biodiversity-productivity relationships. However, the overlooking of the specific role played by key species have limited so far our capacity to comprehensively assess the relative importance of other potential drivers of biodiversity effects.

2. Here, we conducted a grassland diversity-productivity experiment to test how four potential facets of biodiversity effects, namely species richness, functional diversity, species identity and the relaxation of intraspecific competition, account for variations in above and root biomass production.

3. We grew six plant species in monoculture, as well as in every combinations of two, three and six species. Plant density was kept constant across the richness gradient but we additionally grew each species in half-density monoculture to estimate the strength of intraspecific competition for each studied species. We characterized eight functional traits, including root traits, related to nutrient and light acquisition and computed both the functional dissimilarity and the community weighted mean (CWM) of each trait. We further partitioned aboveground biodiversity effect into complementarity and selection effects.

4. We observed strong positive biodiversity effects on both aboveground and root biomass as well as strong positive complementarity effect. These arose largely from the presence of a particular species (Plantago lanceolata) and from CWM trait values more than from a higher functional dissimilarity in plant mixtures. P. lanceolata displayed the highest intraspecific competition, which was strongly relaxed in species mixtures. By contrast, the presence of Sanguisorba minor negatively affected the productivity of plant mixtures, this species suffering more from interspecific than intraspecific competition.

5. This study provides strong evidences that the search for key species is critical to understand the role of species diversity on ecosystem functioning and demonstrates the major role that the balance between intraspecific and interspecific competition plays in biodiversity-ecosystem functioning relationships. Developing more integrative approaches in community and ecosystem ecology can offer opportunities to better understand the role that species diversity plays on ecosystem functioning.

Methods

We conducted an experiment at the Center for Functional and Evolutionary Ecology, Montpellier, France. We grew six plant species in monoculture (6 combinations), as well as in every combinations of two (15 combinations), three (20 combinations) and six species (1 combination) in a greenhouse with three replicate pots for the monoculture, two and three species combinations and six replicates for the six species combination. Plant species were common European herbaceous species: two grasses (Bromus erectus Huds., Dactylis glomerata L.), two forbs (Plantago lanceolata L., Sanguisorba minor Scop.) and two legumes (Lotus corniculatus L., Trifolium repens L).

After all species had shown first signs of flowering, we cut aboveground parts of plants at the base and separated the six plant individuals to measure aboveground biomass of each individual plant. We evaluated root biomass of each pot. We measured eight functional traits: 1) light-saturated leaf photosynthetic rate per area (Amax, µmolCO2 m-2 s-1); 2) maximum height (cm); 3)Specific leaf area (SLA, m².kg-1); 4) Root inter-branch distance (RID, cm); 5) Specific root length (SRL, m.g-1); 6) Root hair length (RHL, cm); 7) specific root nitrogen absorption rate (Nabs µg 15N m-1 h-1) and 8) deep root fraction.

For each trait, we computed both community weighted mean (CWM) and functional dissimilarity (Fdis) of each plant mixture.

Funding

European Research Council, Award: Grant-ERC-StG-2014-639706-CONSTRAINTS

EC2CO Multivers