Ectomycorrhizal fungal communities associated with Salix viminalis L. and S. dasyclados Wimm. clones in a short-rotation forestry plantation

Two willow clones, Salix viminalis L. and S. dasyclados Wimm., growing in separate blocks in mineral soil in one short-rotation forestry (SRF) plantation in Estonia, were analysed to compare the frequency, structure and species composition of ectomycorrhizal (EM) colonisation on their fine roots. Salix dasyclados had significantly greater EM colonisation on root tips (94%) than S. viminalis (75%). The development of EM and associated fungal structures in fine roots (Hartig net, mantle, Hartig net and mantle combined. surface hyphae, endophyte) was similar for both Salix clones. Nine groups of ectomycorrhizal tips were distinguished on the basis of morphological characterisation. Due to high variability among samples, no significant differences between the Salix clones could be found with respect to the abundance of these morphological groups. In total, nine fungal taxa were identified as fungal associates of the two Salix clones. Identification was based upon amplifying and sequencing the rDNA-ITS region of the fungal associates of the root tips. Phialophora finlandia was the most common fungal associate. Morphological groups with well-defined features (e.g., Tomentella sp.) showed limited taxonomic variation, while groups with ill-defined features contained wider taxonomic variation, including unrelated species (e.g., Laccaria sp., Hebeloma helodes). EM fungal diversity was low and largely comprised species considered as pioneer or early stage fungi. A tendency towards higher EM levels with higher N and organic matter concentrations, and low pH, P and K concentrations were observed when the mean levels of EM colonisation were compared with soil variables. It is suggested that EM colonisation level may be primarily determined by the tree species but that local soil nutrient status also influences colonisation. The quality of root litter produced by the Salix clones is known to differ and this may have a role in determining EM colonisation. (C) 2004 Elsevier B.V. All rights reserved.