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

Abstract

Abstract. Two extensive forest vegetation survey datasets are explored, using ordination and classification, for evidence of in situ regeneration by Pinus strobus (Eastern white pine) and P. resinosa (Red pine). Ordination of tree species contributions to total basal area in 320 upland northern hardwood‐ conifer stands produced distinct stand groups for P.banksiana, P. resinosa, P. strobus and 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. strobus mixes with all other forest types, but P. resinosa is restricted to its own group. Seedlings and trees of P. strobus are 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 to in situ regeneration by P. strobus than 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 of P. 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 as Polytrichum, but is ascribed to the absence of competition and other forms of inhibition in the understorey vegetation and down through the canopy profile. In situ regeneration of P. strobus does, therefore, occur but conditions over the forest landscape are largely restrictive.

Conifer–Angiosperm Interactions: Physiological Ecology and Life History

“…This "storage effect" is embodied by the dynamics of temperate conifer-angiosperm mixtures. Long canopy residence times enable conifers to coexist with angiosperms in many temperate forests, despite infrequent recruitment (Read and Hill, 1988;Lusk and Ogden, 1992;Carleton et al, 1996;Lusk and Smith, 1998). Data reviews have confirmed that conifers are appreciably longer-lived, on average, than angiosperm canopy trees in temperate forests of both Northern and Southern hemispheres (Loehle, 1988;Enright and Ogden, 1995).…”

Northward migrating trees establish in treefall gaps at the northern limit of the temperate–boreal ecotone, Ontario, Canada

“…In the Great Lakes-St. Lawrence forest, red pine (Pinus resinosa Sol. ex Aiton (Pinaceae)) and white pine (Pinus strobus L. (Pinaceae)) are the two dominant tree species over shallow soils of the Canadian Shield and are often codominant in Ontario at latitudes between 45 and 46°N (Carleton et al 1996). These two species, however, diVer greatly in their total abundance and associations with other species at diVerent latitudes.…”

Group and single-tree selection cutting in mixed tolerant hardwood–white pine stands: Early establishment dynamics of white pine and associated species

“…Mixed tol-erant hardwood -white pine stands are often managed under single-tree selection cutting but this method is not necessarily suitable for white pine regeneration, a mid-tolerant species (Lessard et al 1999). In mixedwood forests of Canada and northeastern United States, white pine advance regeneration is often present in very small gaps or under partial canopies, but this species is often suppressed by other vegetation and does not reach later developmental stages (saplings and poles) (Leak et al 1995, Carleton et al 1996. In natural tolerant hardwood stands, it was hypothesized that white pine could regenerate in large canopy openings or in low-density stands.…”