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Does arbuscular and ectomycorrhizal fungal inoculation improve soil aggregate stability? A case study on three tropical species growing in ultramafic Ferralsols

Demenois J., Rey F., Stokes A., Carriconde F.. 2017. Pedobiologia, 64 : p. 8-14.

DOI: 10.1016/j.pedobi.2017.08.003

In many tropical regions, 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 with regard to the effects on soil aggregate stability. We investigated how plant inoculation with arbuscular (AMF) and ectomycorrhizal (ECM) fungi could improve aggregate stability of ultramafic Ferralsols in New Caledonia. We performed inoculations with local AMF and ECM on three endemic plant species 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., the latter species are both ECM hosts. We carried out three treatments for each plant species growing in an ultramafic topsoil, (i) control soil with no plants, (ii) non-inoculated plants and (iii) inoculated plants. Inoculation of C. arundinacea was carried out by adding to the topsoil a suspension of mixed AMF spores. T. glauca and A. gummiferum were inoculated with the ECM fungus Pisolithus microcarpus. After 9¿10 months, aggregate stability, soil organic carbon, above- and below-ground dry biomass and root traits were measured. Results showed that on ultramafic topsoil, AMF and ECM inoculations significantly increased plant growth, modified roots (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. Thus, the inoculation of native plant species with carefully selected mycorrhizal fungi could be an efficient technique to aid in the revegetation of bare slopes.

Mots-clés : nouvelle-calédonie; france

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