Physiognomy and Structure: No Data Available

Floristics: This community is dominated by Pinus strobus. It is often distinguished by a supercanopy of large, old Pinus strobus and scattered Pinus resinosa. The lower layer of the canopy consists mainly of Abies balsamea trees and saplings (Ohmann and Ream 1971). Other trees that may be found in this layer include Betula alleghaniensis, Picea glauca, Thuja occidentalis, Acer rubrum, Acer spicatum, and other trees common to boreal forest landscapes. The tall-shrub layer is moderately to well-developed and consists of Abies balsamea, Acer spicatum, Corylus cornuta, and, less frequently, Amelanchier spp. (Ohmann and Ream 1971, Sims et al. 1989). The low-shrub layer is not well-developed and dominated by Diervilla lonicera, Linnaea borealis, Vaccinium myrtilloides, and Vaccinium angustifolium. The herb stratum is also not well-developed. The deep layer of undecomposed needles that formed the mor humus is not conducive to herb growth (Martin 1959a). Prevalent herbs include Aralia nudicaulis, Eurybia macrophylla (= Aster macrophyllus), Cornus canadensis, Maianthemum canadense, Polypodium virginianum (= Polypodium vulgare), and Pteridium aquilinum. Moss species include Dicranum polysetum and Pleurozium schreberi.

There appear to be two variants of this community. Both are dominated by a supercanopy of white pines. In the first variant of this type in northeastern Minnesota and northwestern Ontario, the understory is dominated by Abies balsamea, and, with no fire regime, the forest appears to succeed to a fir-(birch?) forest (Ohmann and Ream 1970). This type of stand was also found in northeastern Ontario by Martin (1959), in a 25-acre stand estimated to be 100 years old. There were also a few spindly Betula papyrifera trees in the understory. A second variant may be a late-successional stage white pine forest, thought to be 300 years old in the same region, where the understory is dominated by Betula alleghaniensis (= Betula lutea) and Tsuga canadensis. All of the Abies balsamea over 5 cm dbh were dead, although there were many smaller Abies balsamea.

Dynamics:  This community is an early- to mid-successional community. Given the appropriate environmental conditions it can be extremely long-lived. Pinus strobus usually follows the establishment of faster-growing species such as Populus spp., Betula papyrifera, or Acer spp., after a disturbance (Frelich 1992). Following a disturbance, such as a fire, Pinus strobus seedling establishment occurs over a period of 20-30 years, using populations of pines near lakeshores or swamps and individual trees that have survived by chance as a seed-source (Frelich 1992). This community is long-lasting, and on more xeric sites, may live for several hundred years due to the ability of pines to replace themselves. On moister soils in northeastern Minnesota, succession to a balsam fir forest occurs (Grigal and Ohmann 1975). Heinselman (1973) studied a community in northeastern Minnesota (BWCA) that had been protected from fire for 360 years, and described it as a successionally advanced community, with a Pinus strobus supercanopy. The canopy consisted of Thuja occidentalis (up to 296 years old), Picea glauca (up to 185 years old), and some Betula papyrifera (up to 162 years old). Thuja occidentalis saplings were abundant, and there was no Pinus strobus regeneration in the understory. He proposed that 460 years after a fire, succession to either an Abies - Thuja - Picea glauca or a Betula forest would be complete. Although it is an early- to mid-successional species, Pinus strobus has a long lifespan, and can replace itself in the canopy by gap-phase reproduction, allowing the community to sustain itself over several hundred years. This process is threatened, however, by the occurrence of white pine blister rust in at least part of the community''s range, particularly in northern Minnesota.

Fire is an important natural disturbance in this community. Although Pinus strobus does not have the more sophisticated adaptations to fire that Pinus resinosa and Pinus banksiana do, Pinus strobus seedling establishment is favored by post-fire conditions, such as exposed mineral soil and high sunlight. Once established, mature Pinus strobus are able to survive surface fires, and have moderate tolerance to shade. Frelich (1992), in an overview of research done on various Pinus strobus communities, found that it is most abundant in forests with a catastrophic fire rotation period of 150-300 years. This coincides with the fire rotation cycle found in the BCWA in northeastern Minnesota, where Heinselman found that Pinus strobus stands remained largely intact for 150-350 years.

Fire plays an important part in the longevity of the stand. Where there is a frequent surface fire regime, the understory is eliminated by fire, establishing a pine seed bed that allows for pine regeneration (Ohmann and Ream 1971). It was suggested by Ohmann and Ream (1971) that the fire suppression in the BCWA had allowed an extremely well-developed Abies balsamea undercanopy to become established, thus hastening the successional trend towards an Abies balsamea forest.