Growing pressures linked to global warming are prompting governments to put policies in place to find alternatives to fossil fuels. In this study, we compared the impact of tree-length harvesting to more intensive full-tree harvesting on the composition of fungi residing in residual stumps 5 years after harvest. In the tree-length treatment, a larger amount of residual material was left around the residual stumps in contrast to the full-tree treatment where a large amount of woody debris was removed. We collected sawdust from five randomly selected residual stumps in five blocks in each of the tree-length and full-tree treatments, yielding a total of 50 samples (25 in each treatment). We characterized the fungal operational taxonomic units (OTUs) present in each stump using high-throughput DNA sequencing of the fungal ITS region. We observed no differences in Shannon diversity between tree-length and full-tree harvesting. Likewise, we observed few differences in the composition of fungal OTUs among tree-length and full-tree samples using non-metric multidimensional scaling. Using the differential abundance analysis implemented with DESeq2, we did, however, detect several associations between specific fungal taxa and the intensity of residual biomass harvest. For example, Peniophorella pallida (Bres.) KH Larss. and Tephromela sp. were found mainly in the full-tree treatment, while Phlebia livida (Pers.) Bres. and Cladophialophora chaetospira (Grove) Crous & Arzanlou were found mainly in the tree-length treatment. While none of the 20 most abundant species in our study were identified as pathogens we did identify one conifer pathogen species Serpula himantioides (Fr.) P. Karst found mainly in the full-tree treatment.

Wood ash amendment to forest soils contributes to the sustainability of the growing bioenergy industry, not only through decreased wood ash waste disposal in landfills but also by increasing soil/site productivity and tree growth. However, tree growth studies to date have reported variable responses to wood ash, highlighting the need to identify proper application rates under various soil/site conditions to maximize their benefits. We explored the influence of tree species, wood ash nutrient application rates, time since application, stand development stage, and initial (i.e., before wood ash application) soil pH and N on short-term tree growth response to wood ash amendment across eight unique study sites spanning five Canadian Provinces. Jack pine (Pinus banksiana Lamb) had the most positive response to wood ash amendment compared to white (Picea glauca Moench), hybrid (Picea engelmannii x glauca Parry), and black spruce (Picea mariana Miller), where increasing nutrient application rates increased height growth response. In comparison, black spruce had the most negative response to wood ash amendment, where increasing nutrient application rates slightly decreased height growth response. Site as a random effect explained additional variation, highlighting the importance of other unidentified site characteristics. By examining trends in short-term growth response across multiple studies with variable site characteristics, we found growth response differed by tree species and nutrient application rates, and that jack pine is a promising candidate for wood ash amendment. These results contribute to our knowledge of optimal wood ash amendment practices and environmentally sustainable bioenergy production. © 2019 The Authors. GCB Bioenergy published by John Wiley & Sons Ltd

Nous avons étudié l’impact des feux de forêt et de la récolte sur la composition en espèces de trois taxons dominants d’arthropodes qui vivent dans la litière (carabes, araignées et staphylins). Cette étude a été réalisée en 2013 dans le centre-nord de l’Ontario (47°42?N, 83°36?O), dans des peuplements dominés par le pin gris (Pinus banksiana Lamb.), au moyen du piégeage dans des trappes. À l’aide de 222 espèces (12?015 individus), nous avons comparé les effets de la perturbation en utilisant des sites récemment brûlés (3 ans après un feu) et des sites coupés à blanc (3 ans après la récolte; bois en longueur, arbre entier, enlèvement des souches et coupe à la cisaille), ainsi que des peuplements plus vieux à couvert fermé qui se sont régénérés après une coupe à blanc (51 ans après la récolte) ou un feu (92 ans après le feu) en utilisant des arbres de régression multivariée. Les taxons étaient plus semblables dans les trois témoins (incluant le feu récent) que entre les témoins et les traitements impliquant une coupe, ce qui s’explique vraisemblablement par la perturbation accrue de la couverture morte dans les parcelles récoltées. De plus, les taxons étaient différents dans les parcelles plus vieilles (92 ans) issues de feux comparativement aux plus jeunes (51 ans) issues d’une coupe, ce qui indique que les communautés n’avaient pas encore récupéré à la suite de la perturbation due à la récolte, probablement à cause du manque de débris ligneux grossiers dans le peuplement plus jeune. Ces résultats indiquent que les pratiques d’aménagement forestier qui correspondent à une perturbation naturelle de la couverture morte pourraient améliorer les effets à court terme tandis que le maintien de plus de débris ligneux grossiers pourrait réduire la période de récupération des communautés épigées. [Traduit par la Rédaction]

Increased interest in biomass harvesting for bioenergetic applications has raised questions regarding the potential ecological consequences on forest biodiversity. Here we evaluate the initial changes in the abundance, species richness and community composition of rove (Staphylinidae) and ground beetles (Carabidae), immediately following 1) stem-only harvesting (SOH), in which logging debris (i.e., tree tops and branches) are retained on site, and 2) whole-tree harvesting (WTH), in which stems, tops and branches are removed in mature balsam fir stands in Quebec, Canada. Beetles were collected throughout the summer of 2011, one year following harvesting, using pitfall traps. Overall catch rates were greater in uncut forest (Control) than either stem-only or whole-tree harvested sites. Catch rates in WTH were greater than SOH sites. Uncut stands were characterized primarily by five species: Atheta capsularis, Atheta klagesi, Atheta strigosula, Tachinus fumipennis/frigidus complex (Staphylinidae) and to a lesser extent to Pterostichus punctatissimus(Carabidae). Increased catch rates in WTH sites, where post-harvest biomass was less, were attributable to increased catches of rove beetles Pseudopsis subulata, Quedius labradorensis and to a lesser extent Gabrius brevipennis. We were able to characterize differences in beetle assemblages between harvested and non-harvested plots as well as differences between whole tree (WTH) and stem only (SOH) harvested sites where logging residues had been removed or left following harvest. However, the overall assemblage response was largely a recapitulation of the responses of several abundant species.