1. Subordinate plant species and Mycorrhizal Fungi:
Preferential symbiosis association?
P. Mariotte, C. Meugnier, C. Vandenberghe, E. Mitchell, A. Buttler
7ème SER European Conference on Ecological Restoration – 26 August – Avignon

2. Landscape of woody-pastures: Semi-natural ecosystem with high biodiversity but a fragile equilibrium
Commentaires vérifiés le
Biodiversité – C. Vandenberghe

3. Introduction Subordinate species: co-occur with dominants1
Subordinate and dominant species selection for a sample of herbaceous vegetation (Field site of Amburnex, CH)
Subordinate species:
co-occur with dominants
important for biodiversity
high frequency
low relative cover
greater risk of extinction
According to:
J. P. GRIME, Benefits of plant diversity to ecosystems: immediate, filter and founder effects, Journal of Ecology, 1998.

4. Introduction Arbuscular Mycorrhizal Fungi (AMF) :2
Arbuscular Mycorrhizal Fungi (AMF) :
80% of plant species are colonised by AMF
Parasitism and/or symbiosis
Increase surface exchange of roots with soil and enhance N and P acquisition of plant
Increase resistance to stress (drought, pathogens)
Influence the structure, productivity and diversity of plant communities
Subordinate species seems to be more mycorrhizal dependent and profit from AMF

5. Introduction Preliminary results of a field experiment: 15 plots3
Dominants (65,3 to 85,3) and subordinate species (2,8 to 16) in percents per plot
x value = 29% p = 0,018
y value= 3.6%
Preliminary results of a field experiment:
15 plots
Vegetation relevees
AMF community profiles by T-RFLP analysis (DNA)
AMF communities are differentiated by percentage of subordinate and dominant species

6. Methods Site: Swiss Jura Species-rich pasture Species selection:4
Site:
Swiss Jura
Species-rich pasture
Species selection:
7 Subordinates
7 Dominants
Previous competition experiment:
3 subordinate species
5 dominant species
Prunella vulgaris / Achillea millefolium
Agrostis capillaris / Taraxacum officinale
Are subordinate species more competitive in presence of AMF?

7. Methods 5
GREENHOUSE EXPERIMENT collaborations : D. Johnson and M. Van der Heijden
Competition + AMF treatments
11 plant interactions x 2 AMF treatments in 6 blocks (132 pots)
Sterilized sandy soil
+ AMF inoculum
Sterilized sandy soil
11 plant interactions:
4 monocultures
6 mixculture of 2 species
1 mixculture of 4 species
AMF inoculum:
Glomus intraradices
Obligate symbiont

8. Methods Pots design 6 Sterilized seeds in bleach 5% 3 months
Spe 1
Spe 2
Sterilized seeds
in bleach 5%
3 months
Germination on sterilized Agar-agar 1,6 %
2 individuals by species
Transplantation and assembly

9. Methods Measures AMF effect 7 - Above-ground biomass
- Root biomass (collected by washing)
 Dried at 60°C for 72h and weighted
AMF effect
Biomass i growing with j with AMF
Biomass i growing with j without AMF
AMF effect = 0 : no effects of fungi
AMF effect > 0 : Increasing biomass with fungi
AMF effect < 0 : Decreasing biomass with fungi
AMF effect ij = ln

10. Methods Competitive effect 8 Relative Yield per Plant (RYP)
Biomass of species i in mixculture
Biomass of species i in monoculture
Competitive effect = Mean RYPi with each neighbour
RYPi =
Good competitor = high competitive effect / Mean RYP > 1(i.e dominants)
Bad competitor = low competitive effect / Mean RYP < 1 (i.e subordinates)

11. Results 9
Mixculture of 4 species - 2 Dominant and 2 subordinate species
Negative effect on dominant species
No effects on subordinate species
Dominants: decrease of CE
Subordinates : increase of CE
Parasitism on dominants

12. Results 10 AMF effect in subordinates and/or dominants interactions
Negative effects on all species in each combination
More parasitism than symbiosis
Subordinates less affected in subordinate/dominant interactions
Beginning of symbiosis with subordinate ?

13. Results 11
Competitive effect in subordinates and/or dominants interactions
Without AMF
Dominants
Good competitors
Subordinates
Bad competitors
Dominants
Decrease of CE
Loss of competitiveness
Subordinates
Increasing of CE
Grow as in monoculture
With AMF
Without root competition (NRC)

14. Conclusion 12 Arbuscular Mycorrhizal Fungi : Preliminary results
Lead a differential response of subordinate and dominant species
in mixculture of each species and in pairwise interactions between them
Null/low effects on subordinates and very negative on dominants in term of biomass
Reduce competitiveness of dominants species removing negative effects
on subordinates which increase their competitive effect
Promote the competitiveness of subordinate against dominant species
Might be a important factor for persistence of subordinates in plant communities
maintaining high plant diversity

15. Perspectives for new research13
Perspectives for new research
Longer experiment to favour symbiosis instead of parasitism
More dominant and subordinate species involved in polyculture
Different species of arbuscular mycorrhizal fungi
Acknowledgements
Claire Meugnier (University of Neuchâtel, Switzerland)
David Johnson (University of Aberdeen, UK)
Marcel Van der Heijden (Agroscope Reckenholz-Tänikon ART, Switzerland

17. Total biomass in mg Prunella vulgaris Achillea millefolium Taraxacum
officinale
Agrostis
capillaris