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Currently, there are uncertainties regarding the impacts and (or) efficacy of biomass harvesting and silvicultural practices on stand production on coarse-textured boreal soils. Replicated factorial field experiments examining effects of complete vegetation control (repeated glyphosate application) following operational stem-only harvest with disc trenching ([SO.sub.T]), operational whole-tree harvest with ([WT.sub.T]) and without (WT) disc trenching, and whole-tree harvest with complete forest floor removal by blading ([WT.sub.B]) and blading followed by compaction ([WT.sub.BC]) were installed on four sandy northern Ontario jack pine (Pinus banksiana Lamb.) sites. Over 20 years, [WT.sub.B] improved planted- tree survival but decreased longer term stand productivity in comparison with other harvest intensity - soil disturbance treatments. Vegetation control improved tree growth and stand productivity initially, but over time, benefits declined substantially. [SO.sub.T]and WTt had similar impacts on stand production. Disc trenching improved initial planted-tree growth ([WT.sub.T] vs. WT), particularly without vegetation control. Jack pine natural regeneration was greatest with [SO.sub.T], accounting for 25% of stand biomass at year 20. Stand structure effects included increased size inequality of naturals with [WT.sub.B] and reduced size inequality and asymmetry of naturals with vegetation control. Overall, impacts of forest floor removal and natural regeneration on stand development have become increasingly important over time compared with those of vegetation control. Key words: organic matter removal, herbicide, productivity and structure, planting, natural regeneration. A l'heure actuelle, il existe des incertitudes concernant les impacts ou l'efficacite de la recolte de la biomasse et des pratiques sylvicoles sur la production des peuplements etablis sur des sols boreaux a texture grossiere. Nous avons realise des experiences factorielles repetees sur le terrain pour etudier les effets de la maitrise complete de la vegetation (application repetee de glyphosate) a la suite d'une recolte operationnelle par tronc entier avec scarifiage a disque ([TE.sub.S]), d'une recolte operationnelle par arbre entier avec ([AE.sub.S]) ou sans (AE) scarifiage a disque, d'une recolte par arbre entier avec enlevement complet de la couverture morte a l'aide d'un bouteur ([AE.sub.B]) et d'un bouteur suivi de la compaction du sol ([AE.sub.BC]). Ces traitements ont ete appliques sur quatre stations sableuses dominees par le pin gris (Pinus banksiana Lamb.) dans le nord de l'Ontario. Apres plus de 20 ans, la survie des arbres plantes a ete amelioree par le traitement AEB, qui a toutefois diminue la productivite du peuplement a long terme comparativement aux autres traitements impliquant l'intensite de la recolte et la perturbation du sol. La maitrise de la vegetation a initialement ameliore la croissance des arbres et la productivite du peuplement, mais ces gains ont substantiellement diminue avec le temps. Les traitements TES et AES ont produit des impacts semblables sur la production du peuplement. Le scarifiage a disque a ameliore la croissance initiale des arbres plantes ([AE.sub.S] vs AE), particulierement quand il n'y avait pas de maitrise de la vegetation. La regeneration naturelle de pin gris etait plus abondante dans le traitement [TE.sub.S], ce qui correspondait a 25 % de la biomasse du peuplement a 20 ans. Les effets de la structure du peuplement incluaient une augmentation de l'heterogeneite de la taille de la regeneration naturelle dans le traitement AEB et une reduction de l'heterogeneite de la taille et de l'asymetrie de la regeneration naturelle quand la vegetation etait maitrisee. Dans l'ensemble, l'importance des impacts de l'enlevement de la couverture morte et de la regeneration naturelle sur le developpement des peuplements a augmente avec le temps comparativement aux impacts de la maitrise de la vegetation. [Traduit par la Redaction] Mots-cles: enlevement de la matiere organique, herbicide, productivite et structure, plantation, regeneration naturelle., Introduction In many regions, including the boreal forest of Canada, forest biomass harvesting and intensive silviculture programs are now being used to increase fibre utilization and future stand production (Thiffault [...]

Rising demands for forest biomass have raised concerns that the increased removal of organic residues and harvest impacts may reduce longer term site productivity. Replicated field experiments examining the effects of stem-only harvest with disc trenching (S[O.sub.T]), whole-tree harvest with (W[T.sub.T]) and without (WT) disc trenching, whole-tree harvest with forest-floor removal by blading (W[T.sub.B]), and blading followed by compaction (W[T.sub.BC]) were installed on nine sandy jack pine (Pinus banksiana Lamb.) sites in northern Ontario. At year 5, planted-tree diameters, dominant tree heights ([H.sup.D]J, and stand aboveground biomass ([jP.sub.P]Bio) were smaller without soil disturbance (the WT), but were otherwise similar among treatments. At year 15, planted-tree size and stand yield rankings were W[T.sub.T] = S[O.sub.T] = WT > W[T.sub.B] = W[T.sub.BC]. Biomass production by natural regeneration and total stand aboveground biomass (TotBio) treatment rankings were S[O.sub.T] [greater than or equal to] W[T.sub.T] ≥ WT > W[T.sub.B] = W[T.sub.BC]. [H.sub.D], [jP.sub.P]Bio, and TotBio showed increasing divergence over time in W[T.sub.B] vs. W[T.sub.T] - S[O.sub.T] response, whereas statistical equivalence of the W[T.sub.T] and S[O.sub.T] treatments was shown for most tree and stand growth responses. There was some evidence of increasingly negative impacts of W[T.sub.B] as site index declined. Overall, negative W[T.sub.B] effects on tree and stand productivity have become increasingly apparent. Key words: organic matter removal, harvest residue, compaction, blading, whole-tree harvest. La demande croissante de biomasse forestiere souleve la question d'une possible reduction de la productivity des stations a long terme a la suite d'une augmentation du prelevement des residus organiques et des impacts de la recolte. Sur neuf stations sableuses de pin gris (Pinus banksiana Lamb.) du nord de l'Ontario, nous avons etabli des experiences repetees sur le terrain pour etudier les effets de la recolte des tiges seulement avec scarifiage a disque ([TS.sub.D]), de la recolte par arbre entier avec (A[E.sub.D]) et sans (AE) scarifiage a disque, et de la recolte par arbre entier avec l'enlevement de la couverture morte a l'aide d'une lame bineuse (A[E.sub.L]) ou d'une lame bineuse suivie d'une compaction (A[E.sub.LC]). Apres 5 ans, le diametre des arbres plantes, la hauteur des arbres dominants ([H.sup.D]) et la biomasse aerienne des peuplements ([jP.sub.P]Bio) etaient plus faibles sans perturbation du sol (AE), mais similaires entre les autres traitements. Apres 15 ans, le classement des traitements en ce qui concerne la taille des arbres plantes et la production etaient A[E.sub.D] = [TS.sub.D] = AE > A[E.sub.L] = A[E.sub.LC]. Dans le cas de la production en biomasse de la regeneration naturelle et en biomasse aerienne totale des peuplements (BioTot), le classement des traitements etait [TS.sub.D] [greater than or equal to] A[E.sub.D] ≥ AE > A[E.sub.L] = A[E.sub.LC]. Nous avons observe une divergence croissante entre les reactions de A[E.sub.L] vs A[E.sub.D] et [TS.sub.D] en ce qui concerne la [jP.sub.P]Bio et la BioTot en fonction du temps, alors qu'une equivalence statistique des traitements A[E.sub.D] et [TS.sub.D] a ete observee pour la plupart des reactions de croissance des arbres et du peuplement. Le traitement A[E.sub.L] tendait a avoir un impact negatif croissant avec une diminution de l'indice de qualite de station. Generalement, les effets negatifs du traitement A[E.sub.L] sur la productivite des arbres et du peuplement sont devenus de plus en plus apparents. [Traduit par la Redaction] Mots-cles: prelevement de la matiere organique, residus de coupe, compaction, lame bineuse, recolte par arbre entier., Introduction In many regions, the forest industry is broadening its scope to address the use of forest biomass for energy production. This includes the use of harvest residues such as [...]

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Examines the influence of root and butt rots on windfall and mortality of residual trees following partial cutting in Ontario. Measurement of decay at stump level made on cross-sectional discs; Use of laboratory culturing procedures in identifying causal fungi; Association between root rot and windfall.