IMPACTS OF LOGGING AND WILDFIRE ON AN UPLAND BLACK SPRUCE COMMUNITY IN NORTHWESTERN ONTARIO

Plant species composition and community structure were compared among four sites in an upland black spruce community in northwestern Ontario . One site had remained undisturbed since the 1930s and three had been disturbed by either logging, fire, or both logging and fire. Canonica l correspondence ordination analyses indicated that herbaceous species composition and abundance differed among the disturbance types while differences in the shrub and tree strata were less pronounced. In the herb stratum Pleurozium schreberi, Ptilium crista-castrensis and Dicra num polysetum were in greatest abundance on the undisturbed forest sit e, while the wildfire and burned cutover sites were dominated by Epilo bium angustifolium and Polytrichum juniperinum. The unburned harvested site was dominated by Epilobium angustifolium, Cornus canadensis and Pleurozium schreberi. Species richness was lower on the undisturbed si te than on any of the disturbed sites while species diversity (H') and evenness (Hill's E5) were higher on the unburned harvested site than on the other sites. Results suggest that herb re-establishment is diff erent among harvested and burned sites in upland black spruce communit ies and we hypothesize that differences in the characteristics of the disturbance were responsible, in particular, the impact of burning on nutrient availability. These differences need to be taken into account in determining the effects of these disturbances on biodiversity and long-term ecosystem management.