The hypothesis of the present study was that microbial communities would
differentiate under Eucalyptus camaldulensis and that this influence
will modify microbial functional diversity. A further hypothesis was
that an enhancement of arbuscular mycorrhizal (AM) density (through
controlled fungal inoculation) would minimize this exotic plant species
effect through a well-developed mycelium network. Treatments consisted
of control plants, pre-planting fertiliser application and AM
inoculation. After 4 months of culture in autoclaved soil, E.
camaldulensis seedlings were either harvested for growth measurement or
transferred into containers filled with the same soil but not
sterilized. Other containers were kept without E. camaldulensis
seedlings. After 12 months, effects of fertilizer amendment and AM
inoculation were measured on the growth of Eucalyptus seedlings and on
soil microflora. The results clearly show that this plant species
significantly modified soil microbial community. Both the community
structure (assessed by DGGE profiles) and function (assessed by SIR
responses including soil catabolic evenness) were significantly
affected. The changes in the microbial structure and function were
accompanied by disturbances in the composition of the herbaceous plant
species layer. Hence, these results highlight the role of AM symbiosis
in the processes involved in soil bio-functioning and plant coexistence.