Résumé
Ecological restoration in severely disturbed environments can fail because of lack of knowledge of the functioning of the original ecosystem. Nevertheless, facilitating establishment between plant species can help accelerate ecological succession, especially in stressful environments. Mycorrhizal symbiosis plays a key role in plant growth, particularly in harsh environments, and could also play a role in facilitation between plants, as mycorrhizal fungi can form a mycelial network that simultaneously interacts with the root systems of several plant species. In a high-elevation Malagasy tropical rainforest on acidic and iron-rich soil surrounding an active mining site, four genera of ectomycorrhizal plants are locally abundant: Leptolaena, Sarcolaena, Uapaca and Asteropeia. A floristic survey showed that only Asteropeia seedlings can grow on bare soil. Molecular analysis of ectomycorrhizal fungi ITS rDNA enabled us to describe ectomycorrhizal communities and their distribution among these four plant genera. Russulaceae, Boletales, Cortinariaceae and Thelephoraceae are abundant in these forests. There is extensive sharing between ectomycorrhizal communities associated with Asteropeia mcphersonii and other ectomycorrhizal plants. There are also many mycorrhizal fungi species which are common to ectomycorrhizal communities of seedlings and adult trees. This abundance of generalist fungi allows us to envisage the use of A. mcphersonii in the ecological restoration of the mine site. Planting ectomycorrhizal fungi in the bare soil at the beginning of ecological restoration could allow them to grow, thereby establishing a source of inoculum to colonize other ectomycorrhizal plants and consequently facilitate their establishment.