ECOLOGY OF AND CONTROL STRATEGIES FOR CALAMAGROSTIS-CANADENSIS IN BOREAL FOREST SITES

Calamagrostis canadensis (Michx.) Beauv. is a widely distributed rhizo matous grass that can seriously inhibit growth of white spruce (Picea glauca (Moench) Voss) seedlings in the boreal forests of North America . We review the dynamics of this grass during four successional stages : the colonization of disturbed sites; dominance of the site by the gr ass a few years after disturbance; gradual loss of dominance with over story development; and maintenance of the grass at low levels in the u nderstory of the mature forest. We also describe C. canadensis in rela tion to recruitment from clonal growth and seed, environmental conditi ons for growth, the effects of grass litter buildup on conifer seedlin g microclimate, and overall competitive abilities. Control strategies for C. canadensis are as follows. If the grass is found in nearly ever y square metre in the understory prior to logging, there will be rapid spread when the stand is clear-cut unless clones are killed using her bicides or a deep burn. Large spruce seedlings, planted on large soil scalps or mounds, coupled with release by way of herbicides or sheep g razing, may be necessary for plantation establishment under conditions of encroachment by C. canadensis. Alternatively, the shade provided b y a partial canopy may inhibit the grass sufficiently to allow spruce seedlings to establish. If grass is not abundant in the understory, we recommend (i) minimizing forest floor disturbance to reduce sites for grass seedling colonization or (ii) a slash burn with the hope of enc ouraging colonization by herbaceous species that have less impact on c onifer seedlings.