Importance of ectomycorrhizal fungi in ecological restoration of mining sites in New Caledonia, Koniambo Massif

The Koniambo Massif located in the north west of New Caledonia, is mainly composed of peridotite and serpentinite. It constitutes a large nickel deposit (NiO 0,1 to 5%) currently prospected by two mining companies (Falconbridge S.A. and SMSP). The main purpose of this study is to identify native plant/fungus couples adapted to ecological restoration issues. The study consists in a toposequencial analysis of the plant formations, formed of endemic species, and the associated ectomycorrhizal fungi, along a gradient. Four plant formations (1 to 4) were identified along the sequence from a talweg (700m) to a plateau (900m). Formation 1 is characterised by a humid dense forest dominated by Nothofagus (Fagaceae) with a high plant and ectomycorrhizal fungus diversity. Formation 2 is characterised by a shrubby maquis dominated by Tristaniopsis calobuxus and T. guillainii (Myrtaceae). For the first time, these species are described as ectomycorrhizal. Moreover, in this maquis the fungal mycelium forms the matrix for the loose iron nodules (1 to 5 mm) forming the soil. Formation 3 is characterised by a sparse herbaceous maquis dominated by Costularia spp. (Cyperaceae) and Codia montan (Cunoniaceae). (Texte intégral)