Site patterns of natural regeneration following clear-cutting in northwestern Quebec

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Abstract
Pre- and post-harvest regeneration levels were compared for Abiesbalsamea (L.) Mill. –Betulapapyrifera Marsh. –Picea spp. forests in an area of the southern clay belt of northwestern Quebec. Results revealed abundant advance softwood regeneration (mean = 65 000 stems/ha), almost entirely of Abies prior to harvest. The survey following mechanical and manual whole-tree harvesting suggested a 92% reduction of softwood regeneration and a shift from softwood to a mixed or hardwood-shrub dominated regeneration. Ninety percent of softwood seedlings collected after harvest were pre-established. Destruction of advance regeneration was generally greater on fine-textured soils. Hierarchic cluster analysis of ecological types based on softwood, hardwood, and shrub tree regeneration data as variables, revealed nine groups that could serve as a basis for operational silvicultural decision making. In general, Salix spp. and Alnusrugosa (Du Roi) Spreng. are the major competitors on poorly drained sites; Betula sp., Acerspicatum Lam., and Prunuspensylvanica L.f. dominate on thin organic deposits and coarse deposits, whereas Populustremuloides Michx. and Acerspicatum dominate on fine-textured deposits. These findings suggest that a good understanding of physical site factors can provide useful information for harvesting and silvicultural planning.