Ectomycorrhizae formation, seedling health index, and seedling survival were assessed for two-year-old nursery-grown seedlings of Pinus resinosa and Pinus strobus two months after planting in clear-cuts that had received prescribed burning under different fire intensities. Controls consisted of seedlings planted in unburned clear-cuts. Fire intensity positively correlated with percent ectomycorrhizal roots for P. strobus but not for P. resinosa. Seedling health index and survival were highest in burned-over sites as compared to control sites for both pine species. Fire intensity correlated with seedling health index for P. strobus but not for P. resinosa. Fire intensity correlated with seedling survival for both species. Colonization of seedlings by ectomycorrhizal fungi did not correlate with seedling health index or seedling survival. P. resinosa seedlings planted in burned-over sites had a smaller number of lateral roots per unit length primary/secondary roots compared to seedlings planted in control plots.

Eastern white pine (Pinus strobus L.) does not regenerate well in the absence of fire, or without mechanical exposure of mineral soil, while balsam fir (Abies balsamea L. Mill.) is a common understory species on sites occupied by white pine. We conducted two experiments to explain the difference in regenerative success of these two species. First, the effect of shade and soil organic matter on the emergence of white pine and balsam fir were compared using soil monoliths from a regenerating white pine stand. Balsam fir germination was significantly lower than white pine germination at different shade levels and at different levels of soil organic matter. Second, seed predation was compared between balsam fir and white pine in a non-regenerating white pine stand. Predation of white pine seeds was 10 times greater than balsam fir predation even when seeds of white pine and balsam fir were left as a mixture on the forest floor. We speculate that seed predation is a critical factor in white pine succession and that seed predators favour balsam fir succession by selecting white pine seeds.Key words: seed predation, fire ecology, Pinus strobus, Abies balsamea, Peromyscus maniculatus, succession Le pin blanc de l'est (Pinus strobus L.) ne se r6gCnkre pas adauatement en l'absence du feu, ou d'exposition mecanique du sol minCral, tandis que le sapin baumier (Abies balsamea L. Mill.) est une espkce commune du couvert de bas Ctage sur les sites occup6s par le pin blanc. Nous avons entrepris deux essais pour expliquer cette diffkrence dans le taux de r6gCnhtion de ces deux espkces. F'rederement, l'effet de l'ombre et la matikre organique du sol sur 1'Cmergence du pin blanc et du sapin baumier ont Ct C comparCs en utilisant des blocs monolithes de sol tires d'un peuplement de pin blanc en regkneration. La germination du sapin baumier Ctait significativement infkrieure 2 celle du pin blanc selon differents niveaux d'ombrage et selon diffkrents niveaux de presence de matikre organique dans le sol. Deuxikmement, la prCdation des semences a Ct C comparke entre le sapin baumier et le pin blanc dans un peuplement de pin blanc qui n'etait pas en voie de rCgCnCration. La prCdation des semences de pin blanc Ctait dix fois supCrieure ZL celle des semences de sapin baumier mEme lorsque les semences de pin blanc et de sapin baurnier avaient Ct C laisskes sur le parterre forestier sous forme de melange. Nous estimons que la predation des semences est un facteur critique dans la succession du pin blanc et que les prkdateurs de semences favorisent la succession du sapin baumier en choisissant les semences de pin blanc.

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Five distinct ectomycorrhizal morphotypes were recognized on root systems of Fagus grandifolia collected in a maple‐beech woodlot. Three morphotypes showed extensive root branching whereas two had limited root branching. One morphotype, a bright orange, smooth type, was studied in detail anatomically. A compact mantle with few emanating extraradical hyphae covered the root apex of each mycorrhizal lateral. A Hartig net extended around epidermal and hypodermal cells. Roots were mostly diarch and a single‐layered endodermis and a biseriate hypodermis with the inner hypodermis having suberized walls were present in all specimens examined. The mantle, and to a lesser extent the Hartig net, stored lipids, polysaccharides and proteins.