SummaryBoreal forest soils store a major proportion of the global terrestrial carbon (C) and belowground inputs contribute as much as above-ground plant litter to the total C stored in the soil. A better understanding of the dynamics and drivers of root-associated fungal communities is essential to predict long-term soil C storage and climate feedbacks in northern ecosystems.We used 454-pyrosequencing to identify fungal communities across fine-scaled soil profiles in a 5000 yr fire-driven boreal forest chronosequence, with the aim of pinpointing shifts in fungal community composition that may underlie variation in below-ground C sequestration.In early successional-stage forests, higher abundance of cord-forming ectomycorrhizal fungi (such as Cortinarius and Suillus species) was linked to rapid turnover of mycelial biomass and necromass, efficient nitrogen (N) mobilization and low C sequestration. In late successional-stage forests, cord formers declined, while ericoid mycorrhizal ascomycetes continued to dominate, potentially facilitating long-term humus build-up through production of melanized hyphae that resist decomposition.Our results suggest that cord-forming ectomycorrhizal fungi and ericoid mycorrhizal fungi play opposing roles in below-ground C storage. We postulate that, by affecting turnover and decomposition of fungal tissues, mycorrhizal fungal identity and growth form are critical determinants of C and N sequestration in boreal forests.

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.

SummaryA long-term goal of community ecology is to identify spatial and temporal factors that underlie observed community structures. Ultimately, ecologists seek to relate community patterns to ecosystem processes and functions. Since the mid 1990s, ectomycorrhizal (ECM) research has been equipped with tools to identify and fully quantify the taxonomic diversity in below-ground ECM fungal communities in detail and address such questions. Many of the most important functions of terrestrial ecosystems, as well as interactions, between plants take place below ground and mycorrhizal fungi are among the key players in soil ecology. Here the rapidly increasing knowledge of ECM fungal community ecology is reviewed and the prospects discussed for elucidating processes that structure ECM fungal communities and the way in which such knowledge might be integrated with, and advance, the understanding of plant ecology and ecosystem processes.© New Phytologist (2001) 150 : 555 -562

SUMM,1RYCurrent knowledge of tnycorrhizal diversity in arctic and alpine tundra is based nnainly on static survey's of mycorrhizal associations of plant taxa and fruiting patterns of selected ectomycorrhizal fungal species in specific habitats. Within these limitations, it appears that: (1) non-mycorrhizal plants are w^idespread and predominate in certain plant communities; (2) typical arbuscular m^^corrhizal associations are ubiquitous iti low arctic and alpine areas but that the level of root colonization is highly variable; (3) root colonization by dark septate fungi is a common event but that their ecological significance is still unknown; (4) a large number of eetomycorrhizal fungal species are present as symbionts of a relatively few widely distributed shrubs and herbaceous plant taxa; (5) ericaceous plants with ericoid tnycorrhizas dominate large arctic and alpine areas covered by heath comtnunities. Physical environmental features strongly limit and shape species diversity in arctic and alpine tundra. Colddominated environments provide extreme conditions for the establishment and functioning of mycorrhizal associations. Therefore, such systems are simple models to address the ecology and evolution of mycorrhizal symbioses. Molecular methods to identify mycorrhizal fungi on plant roots will resolve questions related to tbe structure and dynamics of conamunities of mycorrhizal fungi in arctic and alpine tundra.

Resupinate thelephoroid fungi (hereafter called tomentelloid fungi) have a world-wide distribution and comprise approximately 70 basidiomycete species with inconspicuous, resupinate sporocarps. It is only recently that their ability to form ectomycorrhizas (EM) has been realized, so their distribution, abundance and significance as mycobionts in forest ecosystems is still largely unexplored. In order to provide baseline data for future ecological studies of tomentelloid fungi, we explored their presence and abundance in nine Swedish boreal forests in which the EM communities had been analysed. Phylogenetic analyses were used to compare the internal transcribed spacer of nuclear ribosomal DNA (ITS rDNA) sequence data obtained from mycobionts on single ectomycorrhizal tips with that obtained from sporocarps of identified tomentelloid fungi. Five species of Tomentella and one species of Pseudotomentella were identified as ectomycorrhizal fungi. The symbiotic nature of Tomentella bryophila, T. stuposa, T. badia and T. atramentaria is demonstrated for the first time. T. stuposa and Pseudotomentella tristis were the most commonly encountered tomentelloid fungi, with the other species, including T. sublilacina, only being recorded from single stands. Overall, tomentelloid fungi were found in five of the studies, colonizing between 1 and 8% of the mycorrhizal root tips. Two of the five sites supported several tomentelloid species. Tomentelloid fungi appear to be relatively common ectomycorrhizal symbionts with a wide distribution in Swedish coniferous forests. The results are in accordance with accumulating data that fungal species which lack conspicuous sporocarps may be of considerable importance in EM communities.