Ectomycorrhizal functional traits mediate plant-soil feedback processes in trace element contaminated soils

The role of ectomycorrhizal (ECM) fungi in the interface between plant and soil environment is key in explaining ecosystem processes and functions, in particular in the recovery of ecosystem services in degraded environments. Using a trait-based approach, we aimed to study how the effects of soil contamination by trace elements on individual trees were mediated by changes in the community composition and functional traits of ECM symbionts. Soil abiotic properties and ECM patterns of colonization were characterised on holm oak trees (Quercus ilex subsp. ballota) in areas with different levels of contamination in the Guadiamar Green Corridor, in SW Spain. A variety of morphological traits were characterised for both the trees and their associated ECM fungal species, as well as the molecular characterisation of ECM fungal communities. ECM communities’ composition was found to be dependent on soil pH, nutrients and contamination levels. The two most abundant ECM fungal taxa, Hebeloma cavipes and Thelephora terrestris, had contrasting distributions: H. cavipes was found in non-contaminated soils while T. terrestris was associated with acidic soils. Among the studied fungal traits, frequency of emanating hyphae was found to be clustered among species in the communities in contaminated soils. The reduction of emanating hyphae in contaminated soils had an effect on the associated trees by reducing their phosphorous uptake. In conclusion, soil contamination acted as an environmental filter to ECM fungal communities which decreased their functional diversity posing a negative effect on holm oaks performance.

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