Review : roles of mycorrhizal symbioses and associated soil microbiomes in ecological restoration

Christine Lethielleux-Juge ^1,2*

• ¹ Laval University, Quebec, Canada
• ² Université du Québec en Abitibi Témiscamingue, Rouyn-Noranda, Quebec, Canada

The ecological roles of AMF are diverse, providing essential nutrients to host plants, tolerance to stress and regulation of metabolic pathways, greatly involved in soil C dynamics, unlocking minerals and promoting reactive Fe minerals. Although spores dispersal modes are still not clearly understood, a strong positive relationship exists between intra- and extra-radical mycelium at ecosystem level.AMF are essential in ecosystem restoration by improving soil attributes, above and belowground biodiversity, seedlings survival, growth and establishment on stressed soils, driving plant succession and preventing plant invasion. AMF inoculants from native and early seral instead of exotics and late seral, consortia instead of few or single species, are more efficient.Plant and AMF communities evolve together after revegetation, fine fescues being among the most resilient species, specially Festuca rubra, which fungal strategies have been recently finely studied. Distinct AMF communities associate with functionnally different plants, related to differences in P and C transportomes and genetic variations within the AMF symbiont. Ligneous species react differently to forest soil inoculations according to their AM or EM status and in dual-mycorrhizal plants, costs and benefits are context dependent, mycorrhizal switch occuring under various abiotic or biotic factors and resource availability.In mine restoration, root colonization is generally very low during the first year post-reclamation, then increased rapidly before stabilizing. Parallely to plant successions, increased soil parameters and decrease of contaminants, AMF diversity increased and changed, affiliated Glomus genera with small spores being completed by Acaulospora or Gigaspora larger spores under southern climates. Similar recovery period was observed for fungal communities in forest restoration, where EMF species dominate and diversity increased with time post-revegetation, influenced by edaphic variables and tree species. Under HM contamination, microorganisms classes, enzymes and AMF efficiency vary with time, soil parameters, restoration treatments, plant species and levels of soil contamination, Proteobacteria and Actinobacteria being often predominant. Dual applications of specific microbial and AMF species induced synergistic effects on plant growth and soil resilience. Under other contaminants, several AMF and microbial consortia proved to favorize plant growth and nutrient availability and decrease soil toxicity. New quality indicators to compare rehabilitation studies are proposed.