Fly ash-aided phytostabilisation of highly trace element polluted topsoils improves the telluric fungal biomass: A long-term field experiment

•A long term field trial on aided phytostabilisation of TE polluted soil was done.•A positive effect of fly ash amendments on fungal biomass was observed.•Aided phytostabilisation increased AMF biodiversity in the polluted forest soil.•Fly ash amendments enhanced AMF colonization of forest tree roots.

Ten years after fly ash (FA) amendments and tree mix plantation (black locust, black alder, sycamore maple, pedunculate oak and white willow), the viability of the telluric microorganisms in a highly trace element (TE) polluted topsoil was studied. Previous to tree plantation, three experimental plots were set up in the field: a non-amended plot (R), an amended plot with silico-aluminous fly ash (F1) and an amended plot with sulfo-calcic fly ash (F2). The arbuscular mycorrhizal fungi (AMF), saprophytic fungal and bacterial biomasses were quantified by the measure of specific lipid markers (phospholipid fatty acids (PLFA) and ergosterol). The highest AMF root colonization was of 18% in the sub-plot of the plot (F1). The highest PLFA C16:1ω5 amount (2 nmol g−1 soil), reported as a marker of the AMF biomass, was recorded in the fly ash amended topsoil compared to the control (R). This result was in accordance with the highest number of AMF spores isolated from the sub-plot of the plot F1. Saprophytic and ectomycorrhizal fungal biomasses were estimated by measuring the PLFA C18:2ω6,9 and ergosterol amounts in the topsoil. Similarly to the PLFA C16:1ω5 amounts, the highest PLFA C18:2ω6,9 amounts (4.7 nmol g−1 soil) were observed in the fly ash amended topsoil compared to the control. However, no significant effect of fly ash amendments was observed on both Gram-positive and Gram-negative specific PLFA. This study demonstrated the usefulness of FA amendments in the assisted phytostabilisation of TE polluted topsoil through the enhancement of fungal population viability.