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A series of spot seeding experiments was set out on coarse-texturd upland sites in northwestern Ontario to investigate how black spruce (Picea marianu [Mill.] B.S.P.) seedling establishment and growth could be improved by site selection and seedbed preparation. Virtually all germination occurred within the first growing season. Annual seedling mortality rates were greatest during the first year, then declined steadily and stabilized at low levels (40%) after the third year. The highest fifth-year establishment ratios (seedlingslviable seed sown) were found on seedbeds derived from materials near the mineral soillhumus interface. On wetter sites (i.e., higher Soil Moisture Regimes) the best seedbeds occurred closer to the soil surface. Mean fifth year establishment ratios for the best seedbeds were 0.032 on moderately h s h to fresh sites, 0.146 on very fresh to moderately moist sites, and 0.082 on moist to very moist sites. On adjacent lowland sites, slow-growing, compact Sphagnum mosses had a mean establishment ratio of 0.179. Mean fifth-year seedling heights on upland sites ranged from 12 to 14 cm, and were not strongly correlated with site or seedbed type.

Root and butt rots are often implicated as causal factors influencing windfall and mortality of residual trees following partial cutting. Measurements of decay at stump level (i.e., the upward extension of root rot) were made on cross-sectional discs taken from windfallen and standing dead 100-to 130-year-old black spruce (Picea mariana (Mill.) BSP) near Nipigon in northwestern Ontario. Subsequently, causal fungi were identified using laboratory culturing procedures. The incidence and amount of decay in windfallen trees within leave strips following alternate strip clearcutting was higher than the general stand levels but lower than that found in windfallen trees in uncut forest. The incidence and amount of decay was also higher in windfallen trees near the centres of the leave strips than in those near the edges and corners of these strips. These results indicate a strong association between root rot and windfall and suggest that for comparable windfirmness, trees near the edges of residual stands must have less decay than those in more sheltered locations. Decay levels tended to be lower on poorly drained sites than on well-drained sites. In uncut forest, and especially in the leave strips, more trees were uprooted than died standing or suffered stem breakage. The incidence and amount of decay tended to be lower in uprooted trees than in standing dead trees or those with stem breakage, although in uncut forest virtually all windfallen or standing dead trees had some degree of stump-level decay. Of the 21 wood-rotting Basidiomycetes isolated from windfallen and standing dead trees, Inonotus tomentosus (Fr.:Fr.) Teng was the most frequent, followed in order by Armillaria ostoyae (Romagn.) Herink, Coniophora puteana (Schum.:Fr.) Karst., and Scytinostroma galactinum (Fr.) Donk. The incidence of I. tomentosus, C. puteana, Xeromphalina campanella (Batsch.:Fr.) Kuhner & Maire, and Serpula himantioides (Fr.:Fr.) Karst., but not Armillaria ostoyae, Scytinostroma galactinum, and Sistotrema brinkmanii (Bres.) Erik., was greater in windfallen and standing dead trees from the leave strips than in the general stand populations. In the leave strips, I. tomentosus, Amylostereum chailletii (Pers.:Fr.) Boid., and Trichaptum abietinum (Dickson:Fr.) Ryv. tended to greater relative abundance in standing dead trees, while the relative abundance of C. puteana and Serpula himantioides was greater in trees with stem breakage. Armillaria ostoyae and Scytinostroma galactinum were as abundant in uprooted trees as in standing dead trees or those with stem breakage. Ascocoryne sarcoides (Jacq.:Fr.) G. & W., a staining fungus that may protect against decay fungi, was frequently isolated in this study.Résumé : Les caries de souches et de racines sont souvent considérées comme des facteurs qui influencent le renversement et la mortalité des arbres résiduels suite à une coupe partielle. Des mesures de la carie dans la souche (i.e., l'extension de la carie de racine vers le haut) ont été prises sur des disques (section radiale) prélevés sur des ...

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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 (SO T ), whole-tree harvest with (WT T ) and without (WT) disc trenching, whole-tree harvest with forest-floor removal by blading (WT B ), and blading followed by compaction (WT 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 D ), and stand aboveground biomass (jP 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 WT T = SO T = WT > WT B = WT BC . Biomass production by natural regeneration and total stand aboveground biomass (TotBio) treatment rankings were SO T ≥ WT T ≥ WT > WT B = WT BC . H D , jP P Bio, and TotBio showed increasing divergence over time in WT B vs. WT T -SO T response, whereas statistical equivalence of the WT T and SO T treatments was shown for most tree and stand growth responses. There was some evidence of increasingly negative impacts of WT B as site index declined. Overall, negative WT B effects on tree and stand productivity have become increasingly apparent.Résumé : La demande croissante de biomasse forestière soulève la question d'une possible réduction de la productivité des stations à long terme à la suite d'une augmentation du prélèvement des résidus organiques et des impacts de la récolte. Sur neuf stations sableuses de pin gris (Pinus banksiana Lamb.) du nord de l'Ontario, nous avons établi des expériences répétées sur le terrain pour étudier les effets de la récolte des tiges seulement avec scarifiage à disque (TS D ), de la récolte par arbre entier avec (AE D ) et sans (AE) scarifiage à disque, et de la récolte par arbre entier avec l'enlèvement de la couverture morte à l'aide d'une lame bineuse (AE L ) ou d'une lame bineuse suivie d'une compaction (AE LC ). Après 5 ans, le diamètre des arbres plantés, la hauteur des arbres dominants (H D ) et la biomasse aérienne des peuplements (jP P Bio) étaient plus faibles sans perturbation du sol (AE), mais similaires entre les autres traitements. Après 15 ans, le classement des traitements en ce qui concerne la taille des arbres plantés et la production étaient AE D = TS D = AE > AE L = AE LC . Dans le cas de la production en biomasse de la régénération naturelle et en biomasse aérienne totale des peuplements (BioTot), le classement des traitements était TS D ≥ AE D ≥ AE > AE L = AE LC . Nous avons observé une divergence croissante entre les réactions de AE L vs AE D et TS D en ce qui concerne la jP P Bio et la BioTot en fonction du temps, alors qu'une équivalence statistique des traitements AE D et TS D a été observée pour la plupart des réactions de croissance des arbres et du peuplement. Le traitement AE L tendait à avoir un impact négatif croissant avec une diminution de l...