Managing succession in conifer plantations: converting young red pine (Pinus resinosa Ait.) plantations to native forest types by thinning and underplanting

The effects of thinning on growth and survival of white pine (Pinus strobus L.), white ash (Fraxinus americana L.), and red oak (Quercus rubra L.), and understory plant diversity were examined in a young red pine (Pinus resinosa Ait.) plantation. Five years after thinning, seedling diameter, height, and stem volume were positively correlated with thinning intensity and the size of canopy openings. Percent survival did not differ among thinning treatments, but was significantly higher in white ash and white pine than red oak. Understory vegetation included 113 species, with species richness increasing with thinning intensity and proximity to neighbouring plant communities. Thinning to create relatively large canopy openings in combination with underplanting can promote the natural succession of young pine plantations to native forest species. Keywords: direct seeding, plant diversity, natural regeneration, red oak, restoration, white ash, white pine