Assessment of the recovery of functional diversity of ectomycorrhizal fungal communities in metal polluted soils

Abstract

Ectomycorrhizal (ECM) fungi associate with plants to conform one of the most important symbioses in terrestrial ecosystems, with important incidence in the provision of some ecosystem services. In 1998, a mine tailing spill affected an extensive area in the Guadiamar valley (Seville, Spain), causing a severe pollution by trace elements (TE). Remediation measures included top soil removal and amendments addition, followed by native tree species afforestation. Since then, monitoring activities have recorded several aspects of the biotic and abiotic conditions during the recovery of this degraded land, however, information about the soil organisms and their functional diversity is scarce. ECM fungal communities associated to planted holm oaks (Quercus ilex) were characterized both functional and taxonomically. We recorded 55 operational taxonomic units and found no differences in diversity between polluted and non-polluted plots. However the ECM fungal community composition was found to be dependent on soil characteristics such as pH, Ca and K content and to trace element concentrations. Functionally, a key trait for ecosystem functioning of ECM communities, the hyphal exploration type, was found to be dependent on the TE concentration in soil. This result points out the relevance of functional approaches when studying ecosystem restoration processes.