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Institute
In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.
Biodiversity-multifunctionality relationships depend on identity and number of measured functions
(2017)
Biodiversity ensures ecosystem functioning and provisioning of ecosystem services, but it remains unclear how biodiversity-ecosystem multifunctionality relationships depend on the identity and number of functions considered. Here, we demonstrate that ecosystem multifunctionality, based on 82 indicator variables of ecosystem functions in a grassland biodiversity experiment, increases strongly with increasing biodiversity. Analysing subsets of functions showed that the effects of biodiversity on multifunctionality were stronger when more functions were included and that the strength of the biodiversity effects depended on the identity of the functions included. Limits to multifunctionality arose from negative correlations among functions and functions that were not correlated with biodiversity. Our findings underline that the management of ecosystems for the protection of biodiversity cannot be replaced by managing for particular ecosystem functions or services and emphasize the need for specific management to protect biodiversity. More plant species from the experimental pool of 60 species contributed to functioning when more functions were considered. An individual contribution to multifunctionality could be demonstrated for only a fraction of the species.
Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment
(2010)
The growth form along the continuum from compact phalanx plants to more loosely packed guerilla plants is an important life-history trait in clonal plants. Prerequisite for its evolution is heritable genetic variation. Starting with 102 genotypes of the stoloniferous herb Ranunculus reptans, we performed one selection experiment on spatial spread per rosette as measure of guerillaness (broad-sense heritability 0.198) and another on plasticity in this trait in response to competition (broad-sense heritability 0.067). After two generations, spatial spread was 36.9% higher in the high line than in the low line (realized heritability +/- SE 0.149 +/- 0.039). Moreover, compared with the low line genotypes of the high line had fewer rosettes, a lower proportion of flowering rosettes, a higher proportion of rooted rosettes, more branches per rosette, longer internodes and longer leaves. In the second experiment, we found no significant direct response to selection for high and low plasticity in spatial spread (realized heritability +/- SE - 0.029 +/- 0.063), despite a significant correlated response in plasticity in the length of the first three stolon internodes. Our study indicates a high potential for further evolution of the clonal growth form in R. reptans, but not for its plasticity, and it demonstrates that the clonal growth form does not evolve independently of other clonal life- history characteristics
Insurance effects of biodiversity can stabilize the functioning of multispecies ecosystems against environmental variability when differential species' responses lead to asynchronous population dynamics. When responses are not perfectly positively correlated, declines in some populations are compensated by increases in others, smoothing variability in ecosystem productivity. This variance reduction effect of biodiversity is analogous to the risk- spreading benefits of diverse investment portfolios in financial markets. We use data from the BIODEPTH network of grassland biodiversity experiments to perform a general test for stabilizing effects of plant diversity on the temporal variability of individual species, functional groups, and aggregate communities. We tested three potential mechanisms: reduction of temporal variability through population asynchrony; enhancement of long-term average performance through positive selection effects; and increases in the temporal mean due to overyielding. Our results support a stabilizing effect of diversity on the temporal variability of grassland aboveground annual net primary production through two mechanisms. Two-species communities with greater population asynchrony were more stable in their average production over time due to compensatory fluctuations. Overyielding also stabilized productivity by increasing levels of average biomass production relative to temporal variability. However, there was no evidence for a performance-enhancing effect on the temporal mean through positive selection effects. In combination with previous work, our results suggest that stabilizing effects of diversity on community productivity through population asynchrony and overyielding appear to be general in grassland ecosystems.
The ability of some plant species to dominate communities in new biogeographical ranges has been attributed to an innate higher competitive ability and release from co-evolved specialist enemies. Specifically, invasive success in the new range might be explained by release from biotic negative soil-feedbacks, which control potentially dominant species in their native range. To test this hypothesis, we grew individuals from sixteen phylogenetically paired European grassland species that became either invasive or naturalized in new ranges, in either sterilized soil or in sterilized soil with unsterilized soil inoculum from their native home range. We found that although the native members of invasive species generally performed better than those of naturalized species, these native members of invasive species also responded more negatively to native soil inoculum than did the native members of naturalized species. This supports our hypothesis that potentially invasive species in their native range are held in check by negative soil-feedbacks. However, contrary to expectation, negative soil-feedbacks in potentially invasive species were not much increased by interspecific competition. There was no significant variation among families between invasive and naturalized species regarding their feedback response (negative vs. neutral). Therefore, we conclude that the observed negative soil feedbacks in potentially invasive species may be quite widespread in European families of typical grassland species.
Modelling the competitiveness of clonal plants by complementary analytical and simulation approaches
(1999)
Rapid decay of diversity-productivity relationships after invasion of experimental plant communities
(2004)
We tested whether neighborhood density affects the clonal life history of the stoloniferous plant Ranunculus reptans through selection and genetic drift. After three generations of sexual reproduction of 16 low- and 16 high- density lines, we studied traits related to growth form and reproduction in a common competition free environment. A 7.7% lower branching frequency and slightly longer internodes indicated an evolutionary shift towards a less compact growth form under high neighborhood density, but because stolons grew also more vertically, horizontal spread per ramet was slightly decreased. Neighborhood density had no directional effects on the evolution of allocation to sexual and vegetative reproduction in R. reptans. Variation among replicated high-density lines was significantly lower than among replicated low-density lines in both growth form and reproductive characteristics, indicating less pronounced genetic drift under high neighborhood density. This study demonstrates that a clonal plant can respond to selection imposed by neighborhood density. Moreover, it shows that the effect of random genetic drift increases with decreasing neighborhood density. In a declining species, such as R. reptans in central Europe, this may lower the potential for adaptive evolutionary change and increase extinction risk