Abstract
The maintenance of biodiversity is crucial for ecosystem processes such as plant biomass production, as higher species richness is associated with increased biomass production in plant communities. However, the effects of evenness and functional diversity on biomass production are understudied. We manipulated the composition of an experimental grassland by sowing various seed mixtures and examined the effects of diversity and evenness on biomass production after three years. We found that biomass production increased with greater species and functional richness but decreased with greater species and functional evenness. Standing biomass increased but species number and functional richness decreased with increasing proportion of perennial grasses. Our findings emphasise the importance of productive dominant species, as the proportion of perennial grasses had a positive effect on standing biomass, while species and functional evenness had a negative effect on it. Thus, our findings support the theory that, besides diversity, dominance effects and the so-called mass ratio hypothesis may also play a key role in explaining primary biomass production.
Highlights
Habitat fragmentation, degradation, overexploitation and biological invasions are causing a global decline in biodiversity[1]
Energy enters into terrestrial ecosystems mostly by means of plant biomass production; the impact of global biodiversity loss on plant production indirectly affects all ecosystem processes and associated services provided to humanity[5,6]
Roscher et al.[72] found a significant relationship between total biomass production and total species richness both in weeded and non-weeded plots, but the relationship disappeared in the non-weeded plots when only the sown species were taken into account
Summary
Degradation, overexploitation and biological invasions are causing a global decline in biodiversity[1]. In initial observational studies of mature natural communities[11,12] results usually showed a unimodal (hump-shaped) relationship between biomass production and diversity[9]. More recent studies have presented primary production as the dependent rather than the independent variable[6,17], usually by demonstrating that biomass production generally increases with plant diversity in newly established experimental communities[18,19]. Complementarity effects occur when differences in species resource acquisition in space and time allow a more complete utilization of resources, resulting in the increased biomass production of more diverse communities[22]. Further investigations of the interrelations of species and functional diversity, community structure and biomass production are necessary to advance understanding of biodiversity effects and the underlying processes[33]. As environmental and habitat conditions likely drive functional diversity, the effects of variation in functional diversity should be studied in a given vegetation type to provide meaningful comparisons
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