 Hydnellum peckii can <unk> the heavy metal caesium . In one Swedish field study , as much as 9 % of the total caesium of the topmost 10 cm ( 3 @.@ 9 in ) of soil was found in the fungal mycelium . In general , ectomycorrhizal fungi , which grow most <unk> in the upper organic <unk> of the soil or at the interface between the organic and mineral layers , are involved in the retention and cycling of caesium @-@ 137 in organic @-@ rich forest soils . 
