Solubilisation and colonisation of wood ash by ectomycorrhizal fungi isolated from a wood ash fertilised spruce forest

In Sweden application of granulated wood ash has been suggested as a method to supplement nutrient loss resulting from harvesting of forest residues f or bioenergy production. Mycelia of two ectomycorrhizal fungi Piloderma sp. I and Ha-96-3. were commonly found to colonise ash granules in a wood ash f ertilised spruce forest. Thirty-eight fungal isolates were selected from 10 taxa to investigate the possible role of different ectomycorrhizal Fungi i n nutrient mobilisation from ash. The taxa were Cenococcum geophilum Fr,, P iloderma croceum Erikss, and Hjortst., Piloderma sp. I, Thelephora terrestr is (Ehrenb.) Fr., Tylospora fibrillosa Donk, and five unidentified species, all originating from a wood ash fertilised spruce forest. The isolates wer e tested for their ability to solubilise tricalcium phosphate (TCP) or hard ened wood ash (HWA) in vitro. Ha-96-3, P, croceum and Piloderma sp. I were the only taxa which solubilised TCP. Abundant calcium oxalate crystals were formed in TCP and HWA plates with Piloderma sp. I. Ha-96-3 and two isolate s of P. croceum produced intermediate amounts of crystals. Ha-96-1 and T. f ibrillosa produced low amounts of crystal but no crystal formation was obse rved by any of the other isolates. Piloderma sp. I from HWA plates had sign ificantly higher concentrations of P, compared to P. croceum or Ha-96-3. Pi loderma sp. I and P. croceum were further tested for their ability to colon ise wood ash in microcosms containing intact mycorrhizal associations. Afte r 7 months Piloderma sp. I colonised ash amended patches with a dense, mat like mycelium, whereas P. croceum mycelia avoided the ash patches, Possible differences between these fungi in patterns of carbon allocation were inve stigated by labelling seedlings with (CO2)-C-14. Piloderma sp. I mycelia al located significantly more C-14 to ash patches than P. croceum. P. croceum allocated relatively more C-14 to control patches than to the ash patches. The possible role of ectomycorrhizal fungi in mobilisation of nutrients fro m wood ash is discussed. (C) 2001 Federation of European Microbiological So cieties. Published by Elsevier Science B.V. All rights reserved.