Compared Effects on Metrosideros laurifolia of Arbuscular Mycorrhizal Fungal Communities From Restored Laterite and Reference Ultramafic Soil

Abstract

The rehabilitation of mine-impacted areas through ecological restoration can ensure long-term ecosystem resilience by reestablishing at least part of the original biodiversity and ecosystem functions. In New Caledonia, extensive areas of nickel laterite mined land need to be restored. Arbuscular mycorrhizal fungi (AMF) are abundant in New Caledonian serpentine (ultramafic) ecosystems and play important roles in plant development and adaptation to environmental stresses. In a greenhouse experiment using Metrosideros laurifolia, a shrub endemic to New Caledonia, we compared the functional effects of an AMF community extracted from a disturbed soil restored 20 years ago with those of an AMF community from an adjacent undisturbed soil. In the Restored soil, which had extreme chemical conditions, neither AMF communities improved plant growth, unlike in the Reference soil, where a strong mycorrhizal growth response was observed. Additionally, in the Reference soil, plant nutrient uptake was stimulated more by the AMF community from the same soil than by that from the Restored soil. Plant tissue metal concentrations were lower in plants inoculated with the AMF community from the Reference soil. In the Restored soil, total microbial activity was higher in the presence of the AMF community from the Reference soil than in the presence of the AMF community from the Restored soil. Collectively, these results suggest that the AMF community assembled in the Restored soil was less effective at promoting plant productivity than that in the Reference soil.