Short-term effects of cut-to-length versus full-tree harvesting on understorey plant communities and understorey-regeneration associations in Manitoba boreal forests

Abstract

This study compares the effects of full-tree versus cut-to-length forest harvesting methods on understorey community composition and understorey-regeneration associations in jack pine ( Pinus banksiana Lamb.), mixedwood ( Picea glauca (Moench) Voss— Populus tremuloides Michx.— Abies balsamea (L.) Mill.), and black spruce ( Picea mariana (Mill.) BSP) sites 3 years after harvest in southeastern Manitoba, Canada. We found that both harvesting methods affected understorey plant community composition when compared with unharvested control treatments. Harvesting generally decreased the cover of endurer and avoider moss, herb and shrub species characteristic of mature forests, increased the cover of herbaceous and shrubby invader species characteristic of disturbed microsites, and had relatively minor effects on total understorey species richness, diversity and cover. Understorey community responses to harvesting and understorey-regeneration associations after harvesting varied among stand types. In jack pine forests, full-tree harvesting simultaneously promoted P. banksiana regeneration and the growth and establishment of understorey species adapted to disturbed conditions. In mixedwood forests, the cut-to-length harvest method simultaneously promoted P. glauca regeneration and minimized the growth and establishment of potentially competing understorey species. In black spruce forests, there were few differences in the impact of harvesting methods on understorey vegetation. This study suggests that forest managers will need to tailor harvesting methods to the ecological conditions prevalent in different stand types in order to promote understorey and conifer tree regeneration after harvesting.