SUMMARY
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30 Increasing interest has been given to the role of mycorrhizal symbiosis on plant diversity and
31 ecosystem productivity. However much remains unknown about how the diversity of
32 ectomycorrhizal fungi affect plant growth and rhizobial symbiosis. The purpose of this study,
33 undertaken with an Australian Acacia, Acacia mangium, was to investigate the influence of
34 ectomycorrhizal diversity on plant growth, root nodulation with one strain of Bradyrhizobium
35 sp. (Aust 13C strain) and nutrient uptake by creating a gradient of mycorrhizal diversity
36 (ranged from one to six fungal isolates) on A. mangium seedlings in controlled conditions
37 using a P deficient soil. The results clearly show that (i) A. mangium growth is greatly
38 enhanced after ectomycorrhizal fungal inoculation, (ii) there were significant effects of
39 increasing the amount of soil ectomycorrhizal propagules and diversity on whole plant
40 biomass and plant nutrient acquisition and (iii) this ectomycorrhizal promoting effect on this
41 fast-growing leguminous tree is dependent to the functioning of the biological nitrogen-fixing
42 symbiosis. These results emphasize the need to manage soil ectomycorrhizal potential
43 (abundance and diversity of ectomycorrhizal propagules) in forest management practices in
44 order to promote N2 fixation and seedling growth to optimize outplanting performances with
45 fast-growing tree legumes on various reafforestation sites, more particularly in tropical and
46 Mediterranean areas.
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48 Key words: Ectomycorrhizal fungal diversity, nitrogen fixation, tree growth
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