The role of plant functional traits and trait variation for community assembly and productivity in semi-natural and experimentally manipulated grasslands
Final Report Abstract
This project had the objective to address the apparent conflict between contrasting results on diversity-productivity relationships obtained in observational and experimental biodiversity studies in temperate grasslands. We studied species compositions, aboveground biomass production and plant functional traits (1) in subplots of different species richness in twelve semi-natural grasslands in the surroundings of a large grassland biodiversity experiment (Jena Experiment) and 10-year old experimental communities of the Jena Experiment either spontaneously assembled or initially sown with 60 species, and (2) in a species removalenrichment experiment established on six semi-natural grasslands and the experimentally established grasslands of the Jena Experiment. We found that species richness, biomass production and species-level trait expression did not differ largely between semi-natural grasslands and the 10-year old experimentally established grasslands of the Jena Experiment. The most striking differences between the experimental grasslands and the semi-natural grasslands were smaller proportions of grasses and larger proportions of non-legume forbs and legumes in the experimental grasslands sown with 60 species, which also increased their diversity in traits related to nitrogen acquisition (leaf nitrogen concentrations, leaf greenness) and their functional evenness. The spontaneously assembled experimental grasslands had intermediate characteristics. Trait differences between dominant and subordinate species did not vary between semi-natural and experimental grasslands. Dominant species generally grew taller, while subordinate species had larger values of specific leaf area and lower shoot carbon concentrations and leaf greenness suggesting a carbon limitation in spite of their adjustment to canopy shade. The species removal-enrichment experiment resulted in a slight increase in species richness and functional richness after seed addition suggesting a dispersal limitation in the studied grasslands. Species richness and aboveground biomass production did not show significant relationships neither in our comparative studies in semi-natural and different experimentally established grasslands nor in the species removal-enrichment experiment. However, in both experiments trait combinations suggesting an efficient acquisition of light (high community means and low diversity in plant height and large community means in specific leaf area) were positively related with community biomass production. In both experiments, we also found that intraspecific trait variation was similarly important than different species compositions for differences in community trait composition between grasslands. In summary, our results suggest that (1) it is particularly important to account for differences in the functional composition of plant communities when transferring results obtained in biodiversity experiments to natural ecosystems, and (2) that intraspecific trait variation is an important component contributing to site differences in community trait composition and should therefore be considered in analyses of the relationship between trait composition and processes at the community level.
Publications
- (2015) Flooding disturbances increase resource availability and productivity, but reduce stability in diverse plant communities. Nature Communications 6: 6092
Wright AJ, Ebeling A, de Kroon H, Roscher C, Weigelt A, Buchmann N, Buchmann T, Fischer C, Hacker N, Hildebrandt A, Leimer S, Mommer L, Oelmann Y, Scheu S, Steinauer K, Strecker T, Weisser WW, Wilcke W, Eisenhauer N
(See online at https://doi.org/10.1038/ncomms7092)
