Interpreting the effects of plant species diversity and genotypic diversity within a dominant species on above- and belowground overyielding

Biodiversity loss, either intraspecific or interspecific level, could alter community processes and ecosystem function-ing. Exploring the mechanisms by which biodiversity at different levels influences ecosystem functioning is a major challenge in the field of ecology. In this study, by constructing plant communities with different diversity levels of both dominant species (Stipa grandis) genotype and common species in a mesocosm experiment, we analyzed the relative importance of dominant genotype diversity and common species diversity on biomass production through Fox's tripartite partition, and the relationships between community functional diversity and biomass pro-duction. For common species mixtures (G0S5), a significant positive net diversity effect on belowground biomass was found, and the net effect was contributed by a significant positive dominance effect and a significant negative trait-independent complementarity effect. For genotype mixtures of S. grandis (G5S0), a significant positive net di-versity effect on aboveground biomass and a non-significant positive net diversity effect on belowground biomass were found, and both the effects were driven by positive trait-independent complementarity effects. The increases in both dominant genotype and common species diversity (G5S5) led to remarkable positive net diversity effects, with a significant positive trait-independent complementarity effect on belowground biomass and all the three bio-diversity effect components on aboveground biomass being significantly positive. Only a small proportion (3/22) of relationships between community functional diversity and biomass were linear by a first order polynomial estima-tion. The significant positive trait-independent complementarity effect in G5S0 and trait-dependent complementar-ity effect in G5S5 could not be explained by the smaller intraspecific trait variation. These findings highlight the underestimated and overlooked roles of dominant genotypic diversity for ecosystem functioning, and are very im-portant for grassland protection and management, especially in the semi-arid typical steppe . (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

Biodiversity loss can affect community processes and ecosystem functioning. This study explored the impact of different levels of biodiversity on biomass production in plant communities, finding that dominant genotypic diversity plays an important role in aboveground biomass production. The relationships between community functional diversity and biomass were mostly nonlinear.