Community biomass is driven by dominants and their characteristics –the insight from a field biodiversity experiment with realistic species loss scenario

1. Revealing the role of biodiversity in ecosystem functioning (BEF) has
been a major focus of ecological research over recent decades. In general,
results from artificially assembled communities point to the important
role of biodiversity showing that the loss of species has a negative
effect on various ecosystem functions (mostly assessed by aboveground peak
biomass). However, the evidence from manipulations of natural communities
is scarce and results are often contradictory between these two
approaches. In particular, the importance of species dominance for
ecosystem functioning remains poorly understood. 2. We created a gradient
of plant species richness in a meadow community following a realistic
species loss scenario (removal of less abundant species) to test the
effect of diversity on community biomass and assess the importance of
subordinate species compared to dominants in a five-year experiment. 3.
Contrasting with the results of BEF experiments with artificial assembly,
we did not find any relationship between plant species diversity and
aboveground biomass across the timeframe of the experiment. We provide
evidence that dominant species’ identity and traits are the main drivers
of community biomass, because dominant species were able to maintain
biomass production after substantial species loss. Further, dominants
prevented community biomass from declining and biomass was indirectly
influenced not by species richness but through differences in functional
diversity. Our results support the mass ratio hypothesis, showing a much
bigger effect of dominant species on community biomass production and
hints at the rather minor importance of the complementarity effect between
species. We emphasize that BEF research should more focus on the role of
dominant species in maintaining various ecosystem functions. 4. Synthesis.
Species diversity is a poor predictor of community aboveground biomass
production and dominant species can effectively compensate the total
production after substantial loss of other species in a grassland
community.