The mycelium extending from ectomycorrhizal fine roots is thought to be an important inoculum source for outplanted seedlings. The purpose of this study, carried out at a subalpine forest in British Columbia, was to investigate the effect of three different clear-cut sizes: 0.1, 1.0, and 10 ha, on the persistence and diversity of ectomycorrhizae. Over the course of the study, a total of 39 distinct mycorrhizal types were observed. The dominant types matched descriptions of E-strain mycorrhizae and of mycorrhizae formed by Cenococcum spp., two types of Lactarius spp., Piloderma spp., Hebeloma spp., Amphinema spp., and Cortinarius spp. One growing season after tree removal, there were no differences between the treatments in the numbers of active fine roots at any location nor were there any effects on the diversity of ectomycorrhizae with treatment. Two and three growing seasons after logging the persistence of some of the main morphotypes differed with treatment. Although there were no differences in the diversity indices at corresponding distances within the different opening sizes, after two and three growing seasons the numbers of active fine roots as well as the diversity of ectomycorrhizae in clearcuts was significantly reduced with distance from the forest edge.

The Sicamous Creek silviculture systems trial, which is located at a subalpine forest, comprises five replicated treatments. One-third of the timber volume was removed from 30-ha treatment units using cutblocks of 0.1, 1.0, or 10 ha or single-tree selection. Openings were mechanically site prepared by mounding and planted with nurserygrown containerized Picea engelmannii Parry ex Engelm. seedlings. Seedlings were planted in mineral soil exposed by mounding in all four of the harvested treatments as well as in undisturbed soil in the uncut control treatment. Neither the overall ectomycorrhiza colonization nor the number of ectomycorrhizal morphotypes per seedling varied across the cutblocks or among cutblocks of different sizes. This is in contrast to earlier studies at this site that showed inoculum levels to be significantly higher at 2 m from the forest edge, within the rooting zone of forest trees. We hypothesize that the difference here is due either to (i) competition between native ectomycorrhizal fungi and the ectomycorrhizal fungi present on the spruce at planting or (ii) more homogeneous levels of inoculum in the mineral soil exposed by mounding. Fewer native fungi colonized these seedlings than the nonmycorrhizal seedlings from earlier studies, which had been planted between the mounds.Résumé : Le site d'essai de systèmes sylvicoles de Sicamous Creek qui est situé dans une forêt subalpine comprend cinq traitements répétés. Un tiers du volume sur pied a été enlevé dans des unités de 30 ha en utilisant des blocs de coupe de 0,1, 1,0 ou 10 ha ou le jardinage par arbre. Le terrain a été préparé mécaniquement dans les ouvertures en formant des buttes sur lesquelles des semis de Picea engelmannii Parry ex Engelm. en récipient produits en pépinière ont été plantés. Les semis ont été plantés dans le sol minéral exposé par la formation des buttes dans les quatre traitements de récolte aussi bien que dans le sol non perturbé dans le traitement témoin non coupé. Ni la colonisation globale par les ectomycorhizes, ni le nombre de types morphologiques par semis variaient dans l'ensemble des blocs de coupe ou entre les blocs de coupe de différentes dimensions. Ces résultats diffèrent de ceux d'études précédentes sur ce site où le niveau d'inoculum était significativement plus élevé à 2 m de la bordure de la forêt, dans la zone d'enracinement des arbres de la forêt. Nous émettons l'hypothèse qu'ici la différence est due soit (i) à la compétition entre les champignons ectomycorhiziens indigènes et les champignons ectomycorhiziens présents sur les semis lors de la plantation ou (ii) à des niveaux d'inoculum plus homogènes dans le sol minéral exposé par la formation des buttes. Moins de champignons indigènes ont colonisé ces semis que les semis non mycorhizés qui avaient été plantés entre les buttes lors d'études précédentes.[Traduit par la Rédaction] Jones et al. 1433

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