Summary• Changes in above-and below-ground ectomycorrhizal species composition are reported following nitrogen addition for 2 yr to a subalpine spruce ( Picea abies ) stand.• The macrofungal sporocarp production was recorded before and during N addition. Belowground ectomycorrhizal diversity was measured by PCR-RFLP analysis of the internal transcribed spacer (ITS) region of rDNA extracted from single mycorrhizal root tips before, and after 1 and 2 yr of fertilization.• Sporocarp surveys showed that diversity of the ectomycorrhizal community was drastically reduced following 1 yr of N addition, whereas the saprobic fungal community was not affected. The impact on belowground ectomycorrhizal diversity was less pronounced with no change either in the number of ectomycorrhizal taxa or in Simpson's index of diversity. However, a change in belowground species composition 2 years after N addition was observed with significant changes in abundances of single species.• Species which produced large sporocarps accounted for 25% of all sampled root tips. At least 44% of all ectomycorrhizas were formed by species belonging to the Thelephoraceae and Corticiaceae, taxa which produce inconspicuous sporocarps.• Addition of N caused a shift in ectomycorrhizal abundance from species forming large sporocarps to species with no or resupinate sporocarps.

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Keywords:wild forest mushrooms / tree growth / biodiversity / forest management / non-wood forest product Abstract • Most of the edible forest mushrooms are mycorrhizal and depend on carbohydrates produced by the associated trees. Fruiting patterns of these fungi are not yet fully understood since climatic factors alone do not completely explain mushroom occurrence.• The objective of this study was to retrospectively find out if changing tree growth following an increment thinning has influenced the diversity patterns and productivity of associated forest mushrooms in the fungus reserve La Chanéaz, Switzerland.• The results reveal a clear temporal relationship between the thinning, the growth reaction of trees and the reaction of the fungal community, especially for the ectomycorrhizal species. The tree-ring width of the formerly suppressed beech trees and the fruit body number increased after thinning, leading to a significantly positive correlation between fruit body numbers and tree-ring width.• Fruit body production was influenced by previous annual tree growth, the best accordance was found between fruit body production and the tree-ring width two years previously.• The results support the hypothesis that ectomycorrhizal fruit body production must be linked with the growth of the associated host trees. Moreover, the findings indicate the importance of including mycorrhizal fungi as important players when discussing a tree as a carbon source or sink. Mots-clés :champignons sauvages forestiers / croissance d'arbre / biodiversité / gestion forestière / production forestière autre que le bois Résumé -La productivité des champignons est-elle favorisée par la croissance des arbres ? Ré-sultats d'une expérience d'éclaircie.• La plupart des champignons comestibles des forêts sont mycorhiziens et dépendent des hydrates de carbone produits par les arbres associés. Le processus de fructification de ces champignons n'est pas encore totalement connu. À eux seuls, les facteurs climatiques ne sont pas en mesure d'expliquer l'apparition d'années pauvres ou riches en champignons.• Cette étude a pour but de vérifier, d'une manière rétrospective, si la modification de la croissance des arbres, induite par une mise en lumière suite à une éclaircie, influence la diversité et la productivité des champignons dans la réserve mycologique de La Chanéaz en Suisse.• Les résultats montrent une relation temporelle nette entre l'éclaircie, la réaction de croissance des arbres et la réaction des communautés de champignons, spécialement pour les espèces ectomycorhiziennes. Nous avons observé une augmentation tant de la largeur des cernes des hêtres autrefois dominés que du nombre de carpophores, conduisant à une corrélation positive entre les deux variables.• La production de carpophores était influencée par la croissance annuelle précédente des arbres. La meilleure concordance a été trouvée entre la production de carpophores et la largeur des cernes deux ans auparavant.• Les résultats sont en accord avec l'hypothèse que la production de c...

The structure of ectomycorrhizal communities was assessed above- and below-ground at three different sites in Switzerland that are dominated by Norway spruce (Picea abies (L.) Karst.). We applied three different approaches to record the ectomycorrhizal species compositions and their spatial structures and compared them among each other. Sporocarp inventories were carried out weekly for 3 years. Belowground, molecular, and morphological analyses of ectomycorrhizal roots were performed. In the 3 years of sporocarp survey, a total of 128 ectomycorrhizal species was observed. Most abundant in number of species were the genera Cortinarius and Russula in all three sites. Using polymerase chain reaction, only 22% of the ectomycorrhizal species observed in sporocarp surveys were detected in mycorrhizas. Species that produce no or inconspicuous sporocarps were most abundant on the root system in all three study sites. The resolution was clearly inferior in morphotype compared with molecular analyses. Spatial analyses of the ectomycorrhizal species composition among subplots revealed high variability within sites. Within sites, spatial structure with positive autocorrelation was observed based on sporocarp data as well as molecular analyses of root tips at the site where the number of analysed mycorrhizas was sufficiently high. No spatial structure could be detected on this scale by morphotype analyses because of the high variability among soil cores. All three methods showed the same site to be separated from the other two based on ectomycorrhizal species compositions. Stand ages and their histories are discussed as possible explanations for these findings.Key words: community structure, ectomycorrhiza, macrofungi, morphotype, ITS RFLP, Picea abies.