Print Report
G328 Populus tremuloides / Symphoricarpos occidentalis / Festuca hallii Woodland Group
Type Concept Sentence: This group occurs in the transition zone from the grasslands of the Great Plains to the boreal forests where Populus tremuloides dominates small woodland patches, which vary from open, grassy to shaded shrub and forb understories.
Common (Translated Scientific) Name: Quaking Aspen / Western Snowberry / Plains Rough Fescue Woodland Group
Colloquial Name: Northwestern Great Plains Aspen Woodland
Hierarchy Level: Group
Type Concept: This aspen woodland group ranges from the North Dakota/Manitoba border west to central Alberta. It occurs in the northern Great Plains, in the boreal forest-prairie grassland transition region. The climate in this region is mostly subhumid low boreal with short, warm summers and cold, long winters. The physiognomy of the area is distinct woodland patches, in moist protected areas on slopes or depressions. Trees are generally short in stature, reaching mature heights of 15-20 m at the northern edge of the range, but averaging 5-10 m on well-drained sites at the southern limit of tree growth in the prairie grasslands. Populus tremuloides dominates this group. Common associates are Populus balsamifera, with an understory of tall shrubs and diverse herbs. In some areas, Picea glauca also occurs, usually as dense stands on north-facing coulee slopes. Populus tremuloides tends to grow in pure stands as distinct copses in the southern part of the range, the size of the clumps becoming more extensive moving north. Some of the common shrubs include Amelanchier alnifolia, Corylus cornuta, Symphoricarpos albus, Symphoricarpos occidentalis, Prunus virginiana, Prunus pensylvanica, Ribes oxyacanthoides, Rosa acicularis, Rosa woodsii, and Salix bebbiana. Common understory herbs include Aralia nudicaulis, Actaea rubra, Cornus canadensis, Maianthemum canadense, and Maianthemum stellatum. On poorly drained sites, Populus tremuloides may be associated with Populus balsamifera, with Cornus sericea and Viburnum opulus important components of the shrub layer. Betula papyrifera becomes more common on the north or on north-facing slopes. These woodland patches are commonly ringed by Symphoricarpos occidentalis on the drier side, moving into the adjacent prairie community, or by wetlands, with a ring of Salix spp., usually Salix discolor, then Salix petiolaris at the water''s edge. Quercus macrocarpa is found sporadically along the Qu''Appelle River valley and its tributaries in Saskatchewan, becoming more common into Manitoba. Common grasses and forbs include Apocynum androsaemifolium, Aralia nudicaulis, Carex siccata, Carex sprengelii, Elymus trachycaulus, Lathyrus spp., Maianthemum stellatum, Maianthemum canadense, Oryzopsis asperifolia, Prosartes trachycarpa, Sanicula marilandica, Schizachne purpurascens, Thalictrum spp., and Vicia americana. Fire and drought constitute the most important dynamics in this group. Much of this region has undulating to hummocky glacial till topography with depressional wetlands (potholes or kettles). Soils under the grasslands are generally Black Chernozems; Dark Grey Chernozems have developed under the woodlands and Gleysols are associated with the wetland patches.
Diagnostic Characteristics: This group comprises moist to dry Populus tremuloides woodlands that occur as individual stands surrounded by plains rough fescue grasslands, often associated with wetlands and brush prairies. Southward the aspen woodlands are more patchy within a grassland matrix; whereas northward, they may form extensive stands, but in either case the woodlands do not have characteristic mix of boreal conifers, such as Larix laricina, Picea glauca, Picea mariana, Pinus banksiana, or Pinus contorta. Clarification of the geographic range of this group and ~Northern Great Plains Tallgrass Aspen Parkland Group (G146)$$ is needed.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: By and large this aspen woodland occurs south of the boreal forest, so typical boreal conifers (upland species of Picea glauca, Pinus banksiana, Pinus contorta) and wetland conifers (Larix laricina, Picea mariana) are essentially absent. Eastward, the degree to which either Quercus macrocarpa or Betula papyrifera are important components of this type needs review. The Peace River parklands in northern Alberta are probably best placed in a Boreal shrubland and grassland (i.e., ~North American Boreal Shrubland & Grassland Macrogroup (M055)$$ and perhaps ~Western Boreal Dry Shrubland & Grassland Group (G359)$$). The group level distinction between this type and ~Northeastern Great Plains Aspen Woodland Group (G146)$$ needs review, as Bird (1961) notes that Quercus macrocarpa is patchy in Manitoba, though most common in the Red River Valley, tall grass region, and prairie grasses are largely absent from the woodlands per se.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Trees are generally short in stature, reaching mature heights of 15-20 m at the northern edge of the range, but averaging 5-10 m on well-drained sites at the southern limit of tree growth in the prairie grasslands. Most stands throughout the Canadian range are dominated by Populus tremuloides, which forms small discrete groves, sometimes consisting of only a single clone of genetically identical trees. Populus tremuloides canopies are relatively diffuse, transmitting ample light for development of dense understory vegetation, including both shrub and herb layers. Herb layers are dominated by forbs, but also include a variety of shade-tolerant grasses and sedges. Canopies of Quercus macrocarpa and Fraxinus pennsylvanica cast more shade than Populus tremuloides canopies, and the understory vegetation is correspondingly less dense. Stand structure also varies with site conditions; stands on sandy soils tend to be shorter and more open than those on fine-textured soils. Populus tremuloides stands in the southern (grassland) parts of the Canadian range are almost always in landscape depressions, where moisture conditions support tree growth, and are often surrounded by a ring of low shrubs (typically Symphoricarpos occidentalis).
Floristics: Populus tremuloides is the overwhelmingly dominant tree species throughout the Canadian range of M151. At the eastern end of this range, Quercus macrocarpa becomes important, especially on drier sites. Populus balsamifera occurs on moist sites in some Populus tremuloides stands. Fraxinus pennsylvanica appears in Populus tremuloides stands at the eastern edge of the range, and forms stands on north-facing valley slopes far out into the mixedgrass prairie. Along the northern edge of the range, Picea glauca, Pinus banksiana, and Betula papyrifera occur occasionally. In the western part of the range, Picea glauca also forms dense stands on steep north-facing walls of "coulees" (i.e., narrow ravines). Important tall-shrub species include Amelanchier alnifolia, Prunus virginiana, Prunus pensylvanica, Corylus spp., and on moist sites, Cornus sericea (= Cornus stolonifera), Salix spp., Viburnum opulus, and Betula occidentalis. Low-shrub species include Symphoricarpos occidentalis, Symphoricarpos albus, Rosa woodsii, Rosa acicularis, Rubus idaeus, and Ribes spp. The dwarf-shrubs Arctostaphylos uva-ursi and Juniperus horizontalis are abundant in Populus tremuloides stands on sandy sites. The herb layer of these forest and woodland patches is almost completely different in species composition from the herbaceous communities of the adjacent prairie grasslands, which contain species that require full sunlight. Common grass and forb species include Apocynum androsaemifolium, Aralia nudicaulis, Carex siccata, Carex sprengelii, Elymus trachycaulus, Lathyrus spp., Maianthemum stellatum, Maianthemum canadense, Oryzopsis asperifolia, Prosartes trachycarpa, Sanicula marilandica, Schizachne purpurascens, Thalictrum spp., and Vicia americana.
Dynamics: Fire and drought likely played a strong role in preventing the woodlands from expanding into the grasslands. Invasion of aspen into the moister grassland areas has been documented with a reduction in fire frequency. Drought years, however, see the retreat of the woodlands. Much of the area where this group once occurred has been converted to agricultural lands. Currently, forest/woodland groves are often subject to livestock grazing, to which they are less resilient than grasslands. Heavy grazing eliminates the taller shrubs and herbs, and removes the most palatable species. Grazing also causes soil disturbance that fosters invasion by exotic plant species. Heavily grazed Populus tremuloides stands are often reduced to a layer of unpalatable low shrubs, such as Symphoricarpos occidentalis, and a layer of exotic grass species such as Bromus inermis or Poa pratensis. Along with overgrazing, conversion to agriculture has significantly decreased the extent and range of natural stands of Great Plains forests and woodlands.
Environmental Description: Climate in the range of this group is mostly subhumid low boreal with short, warm summers and long, cold winters. Undulating to hummocky glacial till predominates this region. The northern boundary of aspen parkland is well-defined by the line north or east of which the presence of conifers produces mixed forest (Zoltai 1975). Although Picea glauca stands do occasionally occur in mesic location within the region, they tend to be uncommon and restricted to valley bottoms or north-facing slopes. Hogg (1994) found that the northern boundary of the Aspen Parkland correlates with moisture limitations that may limit conifer regeneration or that may have resulted in a fire regime too frequent to allow conifer regeneration. Populus tremuloides, however, can persist under a frequent fire regime due to its ability to regenerate by sprouting from the roots.
Geographic Range: This group ranges from the boreal-grassland transition region. It arcs north from North Dakota through southwest Manitoba, angling northwest through Saskatchewan into Alberta.
Nations: CA,US
States/Provinces: AB, MB, ND, SK
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.849198
Confidence Level: Moderate
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.2 Cool Temperate Forest & Woodland Formation | F008 | 1.B.2 |
| Division | 1.B.2.Ne North American Great Plains Forest & Woodland Division | D326 | 1.B.2.Ne |
| Macrogroup | 1.B.2.Ne.1 Bur Oak - Quaking Aspen / Western Wheatgrass Forest Woodland Macrogroup | M151 | 1.B.2.Ne.1 |
| Group | 1.B.2.Ne.1.d Quaking Aspen / Western Snowberry / Plains Rough Fescue Woodland Group | G328 | 1.B.2.Ne.1.d |
| Alliance | A3248 Paper Birch - Quaking Aspen / Beaked Hazelnut Woodland Alliance | A3248 | 1.B.2.Ne.1.d |
Concept Lineage: No Data Available
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: No Data Available
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- Bird, R. D. 1961. Ecology of the aspen parkland of western Canada in relation to land use. Canada Department of Agriculture Publication 1066, Ottawa, ON. 155 pp.
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- Zoltai, S. C. 1975. Southern limit of coniferous trees on the Canadian prairies. Information Report NOR-X-128. Environment Canada, Canadian Forestry Service, Northern Forest Research Centre, Edmonton, Alberta.