Résumé
In many tropical regions, such as New Caledonia, soil erosion from anthropogenic activities and subsequent ecological restoration are major issues. Revegetation would be an efficient way to mitigate soil degradation. Some plant and mycorrhizal species are more useful than others for stabilizing soil aggregates and thus reducing erodibility. However, the utility of inoculating plants with mycorrhizas in tropical regions is not clear in terms of the effects on aggregate stability. We examined if plant inoculation with arbuscular (AMF) and ectomycorrhizal (ECM) fungi could improve aggregate stability of ultramafic Ferralsols. To this purpose, we carried out inoculations with local AMF and ECM on three endemic plant species of New Caledonia grown in a glasshouse: the sedge Costularia arundinacea (Sol. Ex Vahl) Kük., an AMF host, the shrub Tristaniopsis glauca Brongn. & Gris and the tree Arillastrum gummiferum (Pancher ex Brongn. & Gris) Baill., both are ECM hosts. The experiment consisted of three treatments for each plant species: untreated ultramafic topsoil (control), plants only and inoculated plants. Inoculation of C. arundinacea was carried out by adding a suspension of spores and T. glauca and A. gummiferum were inoculated with Pisolithus microcarpus.After 9-10 months, aggregate stability, soil organic carbon (SOC), above- and below-ground dry biomass and root traits were measured and compared to the controls. We showed that, on ultramafic topsoil, AMF and ECM inoculation significantly increased plant growth, modified root traits (especially root length density) and consequently enhanced aggregate stability. Out of the non-inoculated plant species, C. arundinacea had the greatest positive effect on aggregate stability. The association of T. glauca and P. microcarpus was also found to significantly increase aggregate stability. Our results show that the inoculation of native plant species with carefully selected mycorrhizal fungi could be an efficient technique to aid in the recolonisation of bare slopes