Ectomycorrhizal fungal communities in late-successional Swedish boreal forests, and their composition following wildfire

This study was conducted to evaluate the effects of wildfires on ectomycorrhizal (EM) fungal communities in Scots pine (Pinus sylvestris) stands. Below- and above-ground communities were analysed in terms of species richness and evenness by examining mycorrhizas and sporocarps in a chronosequence of burned stands in comparison with adjacent unburned late-successional stands. The internal transcribed spacer (ITS)-region (rDNA) of mycobionts from single mycorrhizas was digested with three restriction enzymes and compared with an ITS-restriction fragment length polymorphism (RFLP) reference database of EM sporocarps. Spatial variation seemed to be more prominent than the effects of fire on the EM fungal species composition. Most of the common species tended to be found in all sites, suggesting that EM fungal communities show a high degree of continuity following low-intensity wildfires. Species richness was not affected by fire, whereas the evenness of species distributions of mycorrhizas was lower in the burned stands. The diversity of EM fungi was relatively high considering that there were only three EM tree species present in the stands. In total, 135 EM taxa were identified on the basis of their RFLP patterns; 66 species were recorded as sporocarps, but only 11 of these were also recorded as mycorrhizas. The species composition of the below-ground community of EM fungi did not reflect that of the sporocarps produced. EM fungal species present in our ITS-RFLP reference database accounted for 54-99% of the total sporocarp production in the stands, but only 0-32% of the mycorrhizal abundance.