The effects of silvicultural disturbances on the diversity of seed-producing plants in the boreal mixedwood forest

The practice of clear-cutting, followed by site preparing with mechanical equipment, planting a single tree species, and applying herbicides, has recently been cited as a procedure that creates monocultures in northern forests. Research on a trembling aspen (Populus tremuloides Michx.) dominated mixedwood provided an opportunity to examine the potential of silvicultural activities to (i) create monocultures, (ii) create opportunities for the establishment of exotic plant species, and (iii) result in the loss of indigenous plant species. Detailed botanical surveys were conducted for up to 5 years post-treatment in four clearcuts that were mechanically site prepared, planted with a single conifer species, and released with either motor-manual, mechanical, or herbicide treatment. Species richness, abundance (foliar cover), diversity indices, and rank abundance diagrams indicate that the treatments had immediate effects, but none created a monoculture during the period of study. We conclude that the use of clear-cutting, mechanical site preparation, planting a single conifer species, followed by release with motor-manual cutting, mechanical cutting, or herbicide spraying, will not create monocultures in the conditions tested. While 37 exotic species were observed, none of them were tree or shrub species. In addition, no net loss of indigenous seed producing plants was detected. Missed strips and patches, which accounted for up to 25% of the sampled area, buffered treatment effects.