Sustainable forest management relies on a diversity of harvesting practices to conserve the variety of stand structures and compositions found in natural forests. Extensive use of clearcuts can homogenize stand structure by removing all the canopy, damage forest soils and destroy older downed woody debris already present within stands. In contrast partial cuts maintain some standing overstory and conserve certain biological legacies like large live trees as well as standing and downed dead wood, and thus should better conserve biodiversity. However, given the large number of species potentially affected by harvest operations, balancing harvesting intensity and conservation of biodiversity requires a clear understanding of habitat requirements of resident organisms and species conservation post-harvest. We examined the impacts of increasing intensities of stem removal (33%, 40%, 66% and 100%) 20 years after harvest on bryophyte communities in three stand types common in the succession sequences of Eastern boreal mixedwood forests that were dominated by trembling aspen, mixedwood and conifers. While many generalist and common forest species were shared among all harvesting levels and forest types, more specialized species like liverworts differed strongly between uncut and clearcut stands. However, liverworts and other specialists differed less between uncut and partial cut stands. Bryophyte species in hardwood dominated stands tolerated more fluctuations in environmental conditions than species in mixed stands. We were unable to find habitat specialists typically associated with coniferous stands and may be related to prior outbreaks of spruce budworm that occurred 30 years ago. Our results highlight how harvest intensity and forest stand type interact to affect bryophytes and how intact stands may be required to conserve many species that are sensitive to any degree of harvesting.

With climate change, climatic optima are shifting poleward more rapidly than tree migration processes, resulting in a mismatch between species distributions and bioclimatic envelopes. Temperate hardwood tree species may take advantage of the release of climate constraints and forest management to migrate into the boreal forest. Here, we use the SORTIE-ND forest simulation model to determine the potential for the persistence of three temperate species (sugar maple, red maple and yellow birch) when introduced at seedling stage in typical balsam fir–paper birch (BF–PB) bioclimatic domain stands of eastern Canada, quantifying the consequences on the native species composition. SORTIE-ND is a spatially explicit, individual-based forest stand model that simulates tree growth, regeneration and mortality. We performed a novel parameterization of the SORTIE-ND tree growth equation allowing for the inclusion of climate modifiers on tree growth. After validating our model with data from permanent forest inventory plots, we modeled the dynamics of unharvested stands at different successional stages, as well as post-harvest stands, after the addition of sugar maple, red maple and yellow birch seedlings at different densities. Our results show that current BF–PB domain climate conditions do not limit growth and survival of temperate species in boreal stands. Of the temperate species introduced, sugar maple had the lowest ability to grow and survive by the end of the simulation. Species assemblages of host stands were impacted by the presence of temperate species when the addition of seedlings was above 5000 temperate seedlings per hectare at the beginning of the simulation. For stands that were recently clear cut, temperate seedlings were unable to grow due to intense competition from aspen regeneration. Our results suggest that both current climate and competitive interactions between temperate species and boreal species should not impede the ability of temperate species to grow and survive in the BF–PB domain.