In situregeneration ofPinus strobusandP. resinosain the Great Lakes forest communities of Canada

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Abstract
Two extensive forest vegetation survey datasets are explored, using ordination and classification, for evidence ofin situregeneration byPinus strobus(Eastern white pine) andP. resinosa(Red pine). Ordination of tree species contributions to total basal area in 320 upland northern hardwood‐ conifer stands produced distinct stand groups forP.banksiana, P. resinosa,P. strobusand mesic hardwoods in an ascending sequence along the first axis.Quercus rubra(red oak),Q. alba(white oak) and tolerant conifer groups formed segregates from the hardwood complex along the second axis.P. strobusmixes with all other forest types, butP. resinosais restricted to its own group. Seedlings and trees ofP. strobusare more abundant than saplings, which are restricted to the pine and oak forests. Therefore, seed production, dispersal and seedling establishment seem to be less of a barrier toin situregeneration byP. strobusthan subsequent survival and growth.Canonical correspondence analysis of 170 pine‐dominated stands from the Canadian Shield of Ontario, in which tree species variables are segmented into height‐class pseudo‐ species, yielded no linear relationship between environmental features or stand structure and seedling densities ofP. strobus. However, total tree basal area appears to impose an upper limit to seedling density on the forest floor. Strong correlations emerged between pine seedling density and understorey vegetation. Stand classification of the understorey vegetation, using constrained indicator species analysis, yielded distinct high and low seedling groups. Low pine seedling density was associated with abundant broadleaved shrubs, herbs and seedlings as well as feathermosses and tolerant conifers. High seedling density could not be ascribed to the presence of seedbed taxa, such asPolytrichum, but is ascribed to the absence of competition and other forms of inhibition in the understorey vegetation and down through the canopy profile.In situregeneration ofP. strobusdoes, therefore, occur but conditions over the forest landscape are largely restrictive.