Ectomycorrhizal fungal biomass in roots and uptake of P from apatite by Pinus sylvestris seedlings growing in forest soil with and without wood ash amendment

Forest soil from an experimental Norway spruce forest with four levels of wood ash addition (0, 1, 3 and 6 tonnes ha^–1) was used to inoculate pine (Pinus sylvestris) seedlings with indigenous ectomycorrhizal (EM) fungi. Uptake of ³²P and ⁸⁶Rb in a root bioassay was used to estimate the demand for P and K by seedlings grown in the different soils. Utilisation of P from apatite was tested in a laboratory system where uptake by the ectomycorrhizal mycelium was separated from uptake by roots. The demand for P and K in the seedlings was similar regardless of the ash treatment. Variation in EM levels, estimated as fungal biomass (ergosterol) in roots, was large in the different soils, but not related to ash addition. Uptake of P from apatite was, on average, 23% of total seedling P and was not related to EM levels. It was concluded that the improved P uptake from apatite by EM fungi found in earlier studies is probably not a general phenomenon among EM fungi. The small effect of ash addition on EM levels and P uptake suggests that addition of granulated wood ash is a forest management treatment that will have only minor influence on ectomycorrhizal symbiosis.