Detecting the role of individual species for overyielding in experimental grassland communities composed of potentially dominant species |
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Authors: | Christiane Roscher Jens Schumacher Wolfgang W Weisser Bernhard Schmid Ernst-Detlef Schulze |
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Institution: | (1) Institute of Ecology, University of Jena, Dornburger Strasse 159, 07743 Jena, Germany;(2) Max Planck Institute for Biogeochemistry, P.O.Box 100164, 07701 Jena, Germany;(3) Institute of Stochastics, University of Jena, Ernst-Abbe-Platz 2, 07743 Jena, Germany;(4) Institute of Environmental Sciences, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland |
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Abstract: | Several studies have shown that the contribution of individual species to the positive relationship between species richness
and community biomass production cannot be easily predicted from species monocultures. Here, we used a biodiversity experiment
with a pool of nine potentially dominant grassland species to relate the species richness–productivity relationship to responses
in density, size and aboveground allocation patterns of individual species. Aboveground community biomass increased strongly
with the transition from monocultures to two-species mixtures but only slightly with the transition from two- to nine-species
mixtures. Tripartite partitioning showed that the strong increase shown by the former was due to trait-independent complementarity
effects, while the slight increase shown by the latter was due to dominance effects. Trait-dependent complementarity effects
depended on species composition. Relative yield total (RYT) was greater than 1 (RYT > 1) in mixtures but did not increase
with species richness, which is consistent with the constant complementarity effect. The relative yield (RY) of only one species,
Arrhenatherum elatius, continually increased with species richness, while those of the other species studied decreased with species richness or
varied among different species compositions within richness levels. High observed/expected RYs (RYo/RYe > 1) of individual
species were mainly due to increased module densities, whereas low observed/expected RYs (RYo/RYe < 1) were due to more pronounced
decreases in module density (species with stoloniferous or creeping growth) or module size (species with clearly-defined plant
individuals). The trade-off between module density and size, typical for plant populations under the law of constant final
yield, was compensated among species. The positive trait-independent complementarity effect could be explained by an increase
in community module density, which reached a maximum at low species richness. In contrast, the increasing dominance effect
was attributable to the species-specific ability, in particular that of A. elatius, to increase module size, while intrinsic growth limitations led to a suppression of the remaining species in many mixtures.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Complementarity effect Constant final yield Density Dominance effect Relative yield |
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