Print Report
D014 Picea glauca - Picea mariana - Abies balsamea Forest & Woodland Division
Type Concept Sentence: This division is composed of upland forests and woodlands of the boreal and subarctic regions of North America, characterized by the needle-leaved evergreen tree species Abies balsamea, Abies lasiocarpa, Picea glauca, Picea mariana, Pinus banksiana, and Pinus contorta var. latifolia, as well as the broad-leaved cold-deciduous tree species Betula papyrifera, Betula neoalaskana, Populus tremuloides, and Populus balsamifera, ranging in a broad latitudinal belt from Alaska to Labrador and Newfoundland.
Common (Translated Scientific) Name: White Spruce - Black Spruce - Balsam Fir Forest & Woodland Division
Colloquial Name: North American Boreal Forest & Woodland
Hierarchy Level: Division
Type Concept: This division includes the upland boreal, high montane and subarctic forests and woodlands of North America that occupy a wide latitudinal band from Alaska to Labrador and Newfoundland between the arctic and temperate regions. These are mostly needle-leaved evergreen (conifer) forests and woodlands, although broad-leaved cold-deciduous (hardwood) forests and mixed conifer-hardwood forests are also common. Dominant tree species include the conifers Abies balsamea, Abies lasiocarpa, Picea glauca, Picea mariana, Pinus banksiana, and Pinus contorta var. latifolia, and the hardwoods Betula papyrifera, Betula neoalaskana, Populus tremuloides, and Populus balsamifera. Dominance varies across the range of this division, with Betula neoalaskana, Picea glauca, Picea mariana, and Populus tremuloides dominating Alaska-Yukon boreal forests and woodlands, Abies lasiocarpa, Betula neoalaskana, Picea glauca, Pinus contorta var. latifolia, and Populus tremuloides dominating west-central boreal forests and woodlands, and Abies balsamea, Betula papyrifera, Picea mariana, Pinus banksiana, and Populus tremuloides dominating eastern and central forests. Subarctic woodlands are characterized by the prevalence of open-canopied stands of short-statured Picea mariana and/or Picea glauca. At both latitudinal and elevational treelines, woodlands become very sparsely treed and are interspersed with shrublands or tundra. Over most of the range, excluding the Atlantic maritime, landscape patterns and stand dynamics are driven by stand-replacing fire. In the perhumid to oceanic climates of eastern Quebec and Newfoundland and Labrador, fire frequency is reduced and stand dynamics are largely driven by insect epidemics, especially spruce budworm (Choristoneura fumiferana), which primarily attacks Abies balsamea. Picea mariana is maintained on these landscapes through regular, but less frequent, stand-replacing fire.
Much of the North American boreal region is underlain by the Precambrian Shield. However, west of Saskatchewan, the boreal occurs mostly on the Interior Plains and in the mountainous and high plateau landscapes of the North American Cordillera. In the east, the Gaspé Peninsula and the varied geology of the Maritime provinces and insular Newfoundland are exceptions to the subdued topography and nutrient-poor lithology of the Shield. Regional geologic and topographic features produce an array of local site conditions. Permafrost is rare in the southern range of this type but increases in prevalence northward and at higher elevations. In subarctic woodlands, permafrost-affected terrain is widespread on level landscapes and on northern aspects of upland slopes; active (i.e., freeze/thaw) permafrost layers are typically less than a meter deep.
Much of the North American boreal region is underlain by the Precambrian Shield. However, west of Saskatchewan, the boreal occurs mostly on the Interior Plains and in the mountainous and high plateau landscapes of the North American Cordillera. In the east, the Gaspé Peninsula and the varied geology of the Maritime provinces and insular Newfoundland are exceptions to the subdued topography and nutrient-poor lithology of the Shield. Regional geologic and topographic features produce an array of local site conditions. Permafrost is rare in the southern range of this type but increases in prevalence northward and at higher elevations. In subarctic woodlands, permafrost-affected terrain is widespread on level landscapes and on northern aspects of upland slopes; active (i.e., freeze/thaw) permafrost layers are typically less than a meter deep.
Diagnostic Characteristics: Strong diagnostic tree species are Abies balsamea, Betula papyrifera, Betula neoalaskana, Picea glauca, Picea mariana, Pinus banksiana, and Populus balsamifera. Moderate diagnostic trees include Abies lasiocarpa, Pinus contorta var. latifolia, and Populus tremuloides. Some strong to moderate diagnostic understory species include Maianthemum canadense, Viburnum edule, and Vaccinium myrtilloides. Some understory species with moderate diagnostic value are Acer spicatum, Clintonia borealis, Diervilla lonicera, Kalmia angustifolia, Leymus innovatus, Lonicera involucrata, Rosa acicularis, and Vaccinium angustifolium.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: Tree species in this division are strong diagnostics, and only found in the North American boreal. Eurasian boreal forests have a completely different suite of tree species (Saucier et al. 2015).
In the western boreal forests of Canada, the high montane boreal forests and woodlands (including tree islands) are included here, but the scrub/shrub condition is treated as part of the boreal subalpine (shrub/scrub birch shrublands in ~Western Boreal Mesic Birch - Willow Low Shrubland Group (G356)$$).
The subarctic woodland in western Alaska towards the Bering Sea has a strong maritime influence and differs from that of the arctic timberline, especially with the absence of Picea mariana. The western timberline stretches from the vicinity of Kotzebue Sound (at the Arctic Circle) to Katmai National Monument at the base of the Alaska Peninsula (58°N). Well-developed forests extend westward along the floodplains of the major rivers, perhaps encouraged by the lack of permafrost in the active floodplain area.
Areas at the southern limits of the boreal region are termed subboreal. These areas have a flora with both boreal and temperate elements, and although most of the forests in these areas are included in the temperate forest divisions (D194 and D008), some community types, i.e., those with a predominant boreal floristic composition, are placed in this division (D014). There is also some question as to whether high-elevation conifer forests south of the subboreal should be considered as part of D014. These include, for example, subalpine Rocky Mountain and Appalachian spruce - fir forests. At this time, these high-elevation forests of temperate climates are classified in temperate forest and woodland divisions.
In the western boreal forests of Canada, the high montane boreal forests and woodlands (including tree islands) are included here, but the scrub/shrub condition is treated as part of the boreal subalpine (shrub/scrub birch shrublands in ~Western Boreal Mesic Birch - Willow Low Shrubland Group (G356)$$).
The subarctic woodland in western Alaska towards the Bering Sea has a strong maritime influence and differs from that of the arctic timberline, especially with the absence of Picea mariana. The western timberline stretches from the vicinity of Kotzebue Sound (at the Arctic Circle) to Katmai National Monument at the base of the Alaska Peninsula (58°N). Well-developed forests extend westward along the floodplains of the major rivers, perhaps encouraged by the lack of permafrost in the active floodplain area.
Areas at the southern limits of the boreal region are termed subboreal. These areas have a flora with both boreal and temperate elements, and although most of the forests in these areas are included in the temperate forest divisions (D194 and D008), some community types, i.e., those with a predominant boreal floristic composition, are placed in this division (D014). There is also some question as to whether high-elevation conifer forests south of the subboreal should be considered as part of D014. These include, for example, subalpine Rocky Mountain and Appalachian spruce - fir forests. At this time, these high-elevation forests of temperate climates are classified in temperate forest and woodland divisions.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This division includes woodlands and open- to closed-canopy forests, comprising needle-leaved evergreen (conifer), broad-leaved cold-deciduous (hardwood), and mixed needle-leaved and broad-leaved tree species. Woodlands are characteristic of dry site conditions in the southern boreal, and are the zonal condition of the subarctic and high-elevation boreal. Conifer species dominate northern and high-elevation stands; hardwood tree species are more prevalent in the southern boreal. Stands are generally of a simple structure, as frequent disturbances over much of this type limit development of more complex stand structures. The understory ranges from dense shrub and herb/dwarf-shrub layers to open stands with sparse shrubs and herbs and a continuous feathermoss ground layer. Ericaceous species and regenerating conifer tree species are typically prominent in the shrub and herb/dwarf-shrub layers. The moss layer is usually well-developed, especially under conifer canopies, and is typically lichen-dominated in subarctic woodlands.
Floristics: Ten tree species, belonging to three evergreen needle-leaved (Abies, Picea, Pinus) and two broad-leaved cold-deciduous (Betula, Populus) genera, dominate overstory cover in this division. Most of these species occur over much of the range of the division, although geographic predominance does differ and there are some regional species. Betula neoalaskana, Abies lasiocarpa, and Pinus contorta var. latifolia are western species (although only the first occurs in Alaska, and the latter are common across the central and southern Rocky Mountains); Abies balsamea and Pinus banksiana occur in the central and eastern range of this type; Betula papyrifera, Picea glauca, Picea mariana, Populus tremuloides, and Populus balsamifera occur range-wide.
The tree cover of upland eastern forests is characterized by Abies balsamea and Picea mariana, often mixed with Betula papyrifera and/or Populus tremuloides depending upon disturbance history. In the boreal forests of Ontario and western Quebec, Pinus banksiana is common and Populus tremuloides is more prevalent on the landscape than is Betula papyrifera, which is the dominant hardwood in Atlantic boreal forests. Populus tremuloides and Abies balsamea become less common northwards. Picea glauca, which is common but rarely dominant in the eastern boreal, is the dominant upland spruce in western boreal forests, except in the subarctic where Picea mariana is also prevalent. Pinus contorta var. latifolia is typically dominant in early-seral, post-fire Canadian western boreal forests (but it is absent from Alaska and northern Yukon). Populus tremuloides is the most common hardwood species in the west, although Betula papyrifera also occurs. Betula neoalaskana is common in Alaska, Yukon and northern British Columbia. Populus balsamifera co-occurs on moist, generally nutrient-rich sites throughout the full range of this division. Abies lasiocarpa is found in the cordillera, particularly at higher elevations where it codominates with Picea glauca. Larix laricina occurs occasionally in the upland forests of this division. Subarctic woodlands are generally dominated by Picea mariana or Picea glauca, the latter especially west of Manitoba.
Shrub composition varies considerably across the range of this division. Common shrubs of west-central forests are Shepherdia canadensis, Rosa acicularis, and Viburnum edule, along with the dwarf-shrub Vaccinium vitis-idaea. Common dwarf-shrubs of Alaska and the Yukon are Vaccinium uliginosum and Empetrum nigrum. Eastern forest understories are characterized by shrub species such as Kalmia angustifolia, Vaccinium angustifolium, Acer spicatum, and Diervilla lonicera. Subarctic and subalpine woodlands can have well-developed shrub layers of Betula nana/glandulosa and various willows (e.g., Salix glauca, Salix pulchra, Salix richardsonii).
Common herb species are Aralia nudicaulis, Cornus canadensis, and Maianthemum canadense. Clintonia borealis is found in eastern forests, while Chamerion angustifolium and Calamagrostis canadensis are more common in west-central forests. Arctostaphylos rubra (= Arctous rubra) frequently occurs in forests and woodlands of Alaska and Yukon. Festuca altaica is a common grass in subalpine and subarctic woodlands.
Conifer-dominated forests generally have a low cover of shrubs and herbs and a well-developed feathermoss mat covering the ground, composed mostly of Pleurozium schreberi, Hylocomium splendens, and/or Ptilium crista-castrensis; other species include Abietinella abietina, Dicranum spp., and Polytrichum spp. Hylocomium splendens dominates western forests; Pleurozium schreberi dominates eastern forests. The liverwort Bazzania trilobata can be abundant in Atlantic maritime regions. Lichens, such as Cladonia stellaris (= Cladina stellaris), Cladonia arbuscula ssp. mitis (= Cladina mitis) and Stereocaulon spp., become important in the ground layer when the forest cover is more open, and they dominate the ground cover in subarctic woodlands. Subalpine woodlands also have these lichen species but the ground layer is dominated by Hylocomium splendens.
The tree cover of upland eastern forests is characterized by Abies balsamea and Picea mariana, often mixed with Betula papyrifera and/or Populus tremuloides depending upon disturbance history. In the boreal forests of Ontario and western Quebec, Pinus banksiana is common and Populus tremuloides is more prevalent on the landscape than is Betula papyrifera, which is the dominant hardwood in Atlantic boreal forests. Populus tremuloides and Abies balsamea become less common northwards. Picea glauca, which is common but rarely dominant in the eastern boreal, is the dominant upland spruce in western boreal forests, except in the subarctic where Picea mariana is also prevalent. Pinus contorta var. latifolia is typically dominant in early-seral, post-fire Canadian western boreal forests (but it is absent from Alaska and northern Yukon). Populus tremuloides is the most common hardwood species in the west, although Betula papyrifera also occurs. Betula neoalaskana is common in Alaska, Yukon and northern British Columbia. Populus balsamifera co-occurs on moist, generally nutrient-rich sites throughout the full range of this division. Abies lasiocarpa is found in the cordillera, particularly at higher elevations where it codominates with Picea glauca. Larix laricina occurs occasionally in the upland forests of this division. Subarctic woodlands are generally dominated by Picea mariana or Picea glauca, the latter especially west of Manitoba.
Shrub composition varies considerably across the range of this division. Common shrubs of west-central forests are Shepherdia canadensis, Rosa acicularis, and Viburnum edule, along with the dwarf-shrub Vaccinium vitis-idaea. Common dwarf-shrubs of Alaska and the Yukon are Vaccinium uliginosum and Empetrum nigrum. Eastern forest understories are characterized by shrub species such as Kalmia angustifolia, Vaccinium angustifolium, Acer spicatum, and Diervilla lonicera. Subarctic and subalpine woodlands can have well-developed shrub layers of Betula nana/glandulosa and various willows (e.g., Salix glauca, Salix pulchra, Salix richardsonii).
Common herb species are Aralia nudicaulis, Cornus canadensis, and Maianthemum canadense. Clintonia borealis is found in eastern forests, while Chamerion angustifolium and Calamagrostis canadensis are more common in west-central forests. Arctostaphylos rubra (= Arctous rubra) frequently occurs in forests and woodlands of Alaska and Yukon. Festuca altaica is a common grass in subalpine and subarctic woodlands.
Conifer-dominated forests generally have a low cover of shrubs and herbs and a well-developed feathermoss mat covering the ground, composed mostly of Pleurozium schreberi, Hylocomium splendens, and/or Ptilium crista-castrensis; other species include Abietinella abietina, Dicranum spp., and Polytrichum spp. Hylocomium splendens dominates western forests; Pleurozium schreberi dominates eastern forests. The liverwort Bazzania trilobata can be abundant in Atlantic maritime regions. Lichens, such as Cladonia stellaris (= Cladina stellaris), Cladonia arbuscula ssp. mitis (= Cladina mitis) and Stereocaulon spp., become important in the ground layer when the forest cover is more open, and they dominate the ground cover in subarctic woodlands. Subalpine woodlands also have these lichen species but the ground layer is dominated by Hylocomium splendens.
Dynamics: Over most of the range of this division, landscape patterns and stand dynamics are driven by stand-replacing fire (Kenkel et al. 1997, Payette et al. 2008). In the perhumid to oceanic climates of eastern Quebec and Newfoundland and Labrador, fire frequency is reduced and stand dynamics are largely driven by insect epidemics. Northern and high-elevation woodlands can burn less frequently and intensely due to the open stands and their occurrence in cooler environments.
Lightning-caused fires are the most widespread form of natural disturbance in the boreal, particularly in the west (Stockdale 2014), where fire-return intervals can range from about 60 to 120 years. Fires can also be very large in this region. The number and frequency of fires in boreal forests create a mosaic of stands of various ages and composition. Regeneration after fire depends on many factors (Bergeron et al. 2014), including site moisture, post-fire seedbed conditions, species ability to regenerate vegetatively, and seed source. Frequent fires favor Picea mariana, Pinus banksiana, Pinus contorta, Betula papyrifera, and Populus tremuloides, because of their serotinous or semi-serotinous cones or ability to reproduce vegetatively. If available from unburned refugia, Picea glauca seeds also germinate well on mineral seedbeds that are often prepared by fire. Abies balsamea and Abies lasiocarpa do not do well in areas of frequent burning because they lack adaptations for regeneration following severe fire. Abies lasiocarpa is most prevalent at higher elevations of the western Cordillera where fires are less frequent due to cooler temperatures and greater precipitation.
In the moister climates of the eastern boreal, especially in eastern Quebec and the Canadian Atlantic provinces, fires are less frequent (Bergeron et al. 2001) and stand dynamics are primarily driven by insect epidemics, especially by spruce budworm (Choristoneura fumiferana) (Baskerville 1975) or hemlock looper (Lambdina fiscellaria) (Iqbal et al. 2011). These insects primarily attack Abies balsamea, killing adult trees; however, balsam fir stands typically regenerate from a bank of seedlings in the understory. Betula papyrifera and Picea mariana are maintained on these landscapes by regular, but infrequent, stand-replacing fire. Abies balsamea is extremely shade tolerant and regenerates by seed under closed canopies, so with a long fire cycle stands can succeed over time to dominance by Abies balsamea. In the absence of fire, Abies balsamea can self-replace in the canopy by gap dynamics and Picea mariana can regenerate by layering, which is facilitated when the humus thickness increases, thereby perpetuating the black spruce - balsam fir mixture. Bergeron and Fenton (2012) found that in the Eastern Boreal Forest ecozones stands >200 years occupied 20-25% of the landscape, and stands >300 years, some 10-15% of the landscape.
In Atlantic boreal forests, Picea glauca may be favored during insect epidemics, as it is more resistant to spruce budworm defoliation than is Abies balsamea. Picea glauca can also become abundant along coastlines exposed to salt sprays where it often forms dense short, even prostrate, stands. On Anticosti Island, Picea glauca has replaced Abies balsamea as the main tree cover due to grazing pressure from very high populations of white-tailed deer (Odocoileus virginianus) (Côté et al. 2008). Similar conditions have developed in Newfoundland due to moose browsing.
In subarctic woodlands, grazing and trampling by woodland caribou is localized. However, considerable impact has been recorded in northern Quebec and Labrador when population increases of the George River caribou herd in the 1970s resulted in overgrazing of lichen species (Boudreau and Payette 2004). Grazed areas dominated by Cladina spp., particularly Cladina stellaris, were replaced by crustose lichens, Cladonia spp., Cetraria spp., or, in areas of lighter grazing, Stereocaulon spp.
In recent years, mountain pine beetle (Dendroctonus ponderosae) has caused significant mortality to Pinus contorta var. latifolia forests throughout temperate British Columbia (Safranyik and Wilson 2006) and is now spreading northward and eastward into boreal Pinus contorta forests, affecting even hybrid Pinus contorta x banksiana and Pinus banksiana stands in northern Alberta (Nealis and Cooke 2014).
Although the latitudinal treeline has been relatively stable over the last century, it is known from macro-fossil evidence and radiocarbon dating that the treeline was at least 200-300 km north of its present position during the post-glacial climatic optimum (1000-4000 BP). The recession of the treeline is considered to be related to cooler and drier climates that resulted in an increase in fire frequency and a decrease in the capacity of trees to produce viable seeds for successful regeneration at their former positions. The latitudinal treeline is rarely a sharp line but rather a gradual transition to "treed tundra" where arctic-alpine species may occur in the ground vegetation. Short-term fluctuating advances and retreats in tree regeneration with seasonal variation in temperature and moisture have been recorded, and recent reports suggest that there will be directional shift of the treeline further north with climate warming.
Agricultural clearing, forest harvesting and other industrial activities (chiefly petroleum and mining exploration / development) are also significant disturbance factors in some areas.
Lightning-caused fires are the most widespread form of natural disturbance in the boreal, particularly in the west (Stockdale 2014), where fire-return intervals can range from about 60 to 120 years. Fires can also be very large in this region. The number and frequency of fires in boreal forests create a mosaic of stands of various ages and composition. Regeneration after fire depends on many factors (Bergeron et al. 2014), including site moisture, post-fire seedbed conditions, species ability to regenerate vegetatively, and seed source. Frequent fires favor Picea mariana, Pinus banksiana, Pinus contorta, Betula papyrifera, and Populus tremuloides, because of their serotinous or semi-serotinous cones or ability to reproduce vegetatively. If available from unburned refugia, Picea glauca seeds also germinate well on mineral seedbeds that are often prepared by fire. Abies balsamea and Abies lasiocarpa do not do well in areas of frequent burning because they lack adaptations for regeneration following severe fire. Abies lasiocarpa is most prevalent at higher elevations of the western Cordillera where fires are less frequent due to cooler temperatures and greater precipitation.
In the moister climates of the eastern boreal, especially in eastern Quebec and the Canadian Atlantic provinces, fires are less frequent (Bergeron et al. 2001) and stand dynamics are primarily driven by insect epidemics, especially by spruce budworm (Choristoneura fumiferana) (Baskerville 1975) or hemlock looper (Lambdina fiscellaria) (Iqbal et al. 2011). These insects primarily attack Abies balsamea, killing adult trees; however, balsam fir stands typically regenerate from a bank of seedlings in the understory. Betula papyrifera and Picea mariana are maintained on these landscapes by regular, but infrequent, stand-replacing fire. Abies balsamea is extremely shade tolerant and regenerates by seed under closed canopies, so with a long fire cycle stands can succeed over time to dominance by Abies balsamea. In the absence of fire, Abies balsamea can self-replace in the canopy by gap dynamics and Picea mariana can regenerate by layering, which is facilitated when the humus thickness increases, thereby perpetuating the black spruce - balsam fir mixture. Bergeron and Fenton (2012) found that in the Eastern Boreal Forest ecozones stands >200 years occupied 20-25% of the landscape, and stands >300 years, some 10-15% of the landscape.
In Atlantic boreal forests, Picea glauca may be favored during insect epidemics, as it is more resistant to spruce budworm defoliation than is Abies balsamea. Picea glauca can also become abundant along coastlines exposed to salt sprays where it often forms dense short, even prostrate, stands. On Anticosti Island, Picea glauca has replaced Abies balsamea as the main tree cover due to grazing pressure from very high populations of white-tailed deer (Odocoileus virginianus) (Côté et al. 2008). Similar conditions have developed in Newfoundland due to moose browsing.
In subarctic woodlands, grazing and trampling by woodland caribou is localized. However, considerable impact has been recorded in northern Quebec and Labrador when population increases of the George River caribou herd in the 1970s resulted in overgrazing of lichen species (Boudreau and Payette 2004). Grazed areas dominated by Cladina spp., particularly Cladina stellaris, were replaced by crustose lichens, Cladonia spp., Cetraria spp., or, in areas of lighter grazing, Stereocaulon spp.
In recent years, mountain pine beetle (Dendroctonus ponderosae) has caused significant mortality to Pinus contorta var. latifolia forests throughout temperate British Columbia (Safranyik and Wilson 2006) and is now spreading northward and eastward into boreal Pinus contorta forests, affecting even hybrid Pinus contorta x banksiana and Pinus banksiana stands in northern Alberta (Nealis and Cooke 2014).
Although the latitudinal treeline has been relatively stable over the last century, it is known from macro-fossil evidence and radiocarbon dating that the treeline was at least 200-300 km north of its present position during the post-glacial climatic optimum (1000-4000 BP). The recession of the treeline is considered to be related to cooler and drier climates that resulted in an increase in fire frequency and a decrease in the capacity of trees to produce viable seeds for successful regeneration at their former positions. The latitudinal treeline is rarely a sharp line but rather a gradual transition to "treed tundra" where arctic-alpine species may occur in the ground vegetation. Short-term fluctuating advances and retreats in tree regeneration with seasonal variation in temperature and moisture have been recorded, and recent reports suggest that there will be directional shift of the treeline further north with climate warming.
Agricultural clearing, forest harvesting and other industrial activities (chiefly petroleum and mining exploration / development) are also significant disturbance factors in some areas.
Environmental Description: Although the geology and topography within the range of this division is highly diverse, much of the region is underlain by bedrock of the Precambrian Shield. West of Saskatchewan, the boreal occurs mostly on the Interior Plains and in the mountainous and high plateau landscapes of the North American Cordillera. In the east, the Gaspé Peninsula and the varied geology of the Maritime Provinces and insular Newfoundland are exceptions to the subdued topography and nutrient-poor lithology of the shield. Regional geologic and topographic features produce an array of local site conditions.
Climate: The climate of this division is generally boreal continental. Summers are short; winters long; and there can be a large difference between the coldest and warmest temperatures. Precipitation regimes also vary: the driest areas in the western parts of the range receive as low as 165 mm annually, while the wettest areas in the south and east can receive as much as 1200 mm. Higher elevations and northern regions have cooler temperatures overall. In the cordillera, continental effects are modified where higher elevations and mountainous terrain produce cooler summers, warmer winters and more precipitation than is characteristic of areas in the Interior Plains. The Atlantic boreal has a strong maritime influence, with more moderate temperature extremes and high annual precipitation, including considerable snowfall (up to 400 cm), whereas snowfall westward is typically less than 300 cm and maybe as low as 40-100 cm in the west-central boreal region.
Soils/substrate: Almost all of the boreal was glaciated at some time in the Pleistocene (with exceptions in Alaska and parts of Yukon Territory), so glacial till, glaciolacustrine and glaciofluvial materials predominate in landscapes across most of the range of this division. In mountainous areas, colluvial parent materials are also common. Silt caps developed from wind-blown loess are common in the Alaska-Yukon region. Cold soils are common on cool aspects, and humus layers can get fairly thick, especially where fires are infrequent. Permafrost is rare in the southern range of this type but increases in prevalence northward and at higher elevations. In high latitude subarctic woodlands, permafrost-affected terrain is widespread; active (i.e., freeze/thaw) permafrost layers are typically less than a meter deep.
As noted above, much of the boreal is underlain by the Precambrian Shield. Upland soils derived from the igneous and metamorphic rocks of the shield are typically acidic sands and loamy sands. The cordilleran physiographic region has varied geology, consisting of a complex of intrusive igneous and metamorphic rocks (granite, gneiss, schist, phyllite, etc.), some volcanic rock, and flat-lying to gently dipping, sedimentary Paleozoic and Mesozoic rocks. Intrusive igneous rocks of the western cordillera also produce acidic, coarse-textured soils. In contrast, significant areas of the interior and eastern cordillera consist of sedimentary bedrock of Ordovician-Silurian and Middle Devonian carbonates and shales that give rise to basic soils with a loamy texture.
Biogeography: There are several gradients impacting variation among forests and woodlands of this division: (1) latitudinal and elevation impacts on temperature regimes; (2) regional floristic elements across the latitudinal range; and (3) regional floristic elements related to the migration of species after Pleistocene glaciation.
Extensive woodlands occur in a northern latitudinal band across North America and are noticeably distinct in physiognomy from the forests to the south. Woodlands also occur in a predictable pattern at higher elevations, particularly in the western cordillera, but also including some high plateaus of western Canada. A west to east precipitation gradient, especially pronounced with Atlantic maritime influences, impacts forest dynamics and composition as discussed [see Floristics]. Additionally, the tree species Pinus contorta var. latifolia and Abies lasiocarpa replace Pinus banksiana and Abies balsamea in the cordillera of Alberta, British Columbia, and Yukon and Northwest Territories, but these two species are essentially absent from Alaska.
Climate: The climate of this division is generally boreal continental. Summers are short; winters long; and there can be a large difference between the coldest and warmest temperatures. Precipitation regimes also vary: the driest areas in the western parts of the range receive as low as 165 mm annually, while the wettest areas in the south and east can receive as much as 1200 mm. Higher elevations and northern regions have cooler temperatures overall. In the cordillera, continental effects are modified where higher elevations and mountainous terrain produce cooler summers, warmer winters and more precipitation than is characteristic of areas in the Interior Plains. The Atlantic boreal has a strong maritime influence, with more moderate temperature extremes and high annual precipitation, including considerable snowfall (up to 400 cm), whereas snowfall westward is typically less than 300 cm and maybe as low as 40-100 cm in the west-central boreal region.
Soils/substrate: Almost all of the boreal was glaciated at some time in the Pleistocene (with exceptions in Alaska and parts of Yukon Territory), so glacial till, glaciolacustrine and glaciofluvial materials predominate in landscapes across most of the range of this division. In mountainous areas, colluvial parent materials are also common. Silt caps developed from wind-blown loess are common in the Alaska-Yukon region. Cold soils are common on cool aspects, and humus layers can get fairly thick, especially where fires are infrequent. Permafrost is rare in the southern range of this type but increases in prevalence northward and at higher elevations. In high latitude subarctic woodlands, permafrost-affected terrain is widespread; active (i.e., freeze/thaw) permafrost layers are typically less than a meter deep.
As noted above, much of the boreal is underlain by the Precambrian Shield. Upland soils derived from the igneous and metamorphic rocks of the shield are typically acidic sands and loamy sands. The cordilleran physiographic region has varied geology, consisting of a complex of intrusive igneous and metamorphic rocks (granite, gneiss, schist, phyllite, etc.), some volcanic rock, and flat-lying to gently dipping, sedimentary Paleozoic and Mesozoic rocks. Intrusive igneous rocks of the western cordillera also produce acidic, coarse-textured soils. In contrast, significant areas of the interior and eastern cordillera consist of sedimentary bedrock of Ordovician-Silurian and Middle Devonian carbonates and shales that give rise to basic soils with a loamy texture.
Biogeography: There are several gradients impacting variation among forests and woodlands of this division: (1) latitudinal and elevation impacts on temperature regimes; (2) regional floristic elements across the latitudinal range; and (3) regional floristic elements related to the migration of species after Pleistocene glaciation.
Extensive woodlands occur in a northern latitudinal band across North America and are noticeably distinct in physiognomy from the forests to the south. Woodlands also occur in a predictable pattern at higher elevations, particularly in the western cordillera, but also including some high plateaus of western Canada. A west to east precipitation gradient, especially pronounced with Atlantic maritime influences, impacts forest dynamics and composition as discussed [see Floristics]. Additionally, the tree species Pinus contorta var. latifolia and Abies lasiocarpa replace Pinus banksiana and Abies balsamea in the cordillera of Alberta, British Columbia, and Yukon and Northwest Territories, but these two species are essentially absent from Alaska.
Geographic Range: This division occurs across northern North America from northern interior Alaska east through Yukon and Northwest Territories, southern Nunavut and northern Manitoba, Ontario and Quebec to Labrador and Newfoundland. Its southern boundary extends from central British Columbia through Alberta and Saskatchewan, southern Manitoba, Ontario and Quebec, and northern New Brunswick and Cape Breton Island, with possible extensions in the upper Great Lakes states of the United States.
Nations: CA,US
States/Provinces: AB, AK, BC, LB, MB, MI?, MN?, NB?, NF, NT, NU, ON, QC, SK, YT
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.860385
Confidence Level: High
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
| Type | Name | Database Code | Classification Code |
|---|---|---|---|
| Class | 1 Forest & Woodland Class | C01 | 1 |
| Subclass | 1.B Temperate & Boreal Forest & Woodland Subclass | S15 | 1.B |
| Formation | 1.B.4 Boreal Forest & Woodland Formation | F001 | 1.B.4 |
| Division | 1.B.4.Na North American Boreal Forest & Woodland Division | D014 | 1.B.4.Na |
| Macrogroup | 1.B.4.Na.1 Eastern North American Boreal Forest Macrogroup | M495 | 1.B.4.Na.1 |
| Macrogroup | 1.B.4.Na.3 White Spruce - Black Spruce - Kenai Birch Forest Macrogroup | M156 | 1.B.4.Na.3 |
| Macrogroup | 1.B.4.Na.4 North American Northern Boreal Woodland Macrogroup | M179 | 1.B.4.Na.4 |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: = Alaska-Yukon, West-Central and Eastern floristic subdivisions (Saucier et al. 2015) [Report describes entire Boreal forest.]
>< Boreal Forest Region (Rowe 1972)
< North American Boreal Zone (Brandt 2009) [Boreal zone also includes non-treed vegetation communities and wetlands.]
>< Taiga and Boreal Forest (Elliott-Fisk 2000)
>< Boreal Forest Region (Rowe 1972)
< North American Boreal Zone (Brandt 2009) [Boreal zone also includes non-treed vegetation communities and wetlands.]
>< Taiga and Boreal Forest (Elliott-Fisk 2000)
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