'' ("trembling" or "quaking" aspen) is the dominant tree species of the parkland belt. Shown here in fall colours in west of Saskatoon, Saskatchewan. Four significantly different habitats are common in the aspen parklands: The
fescue prairie, the woodlands, the ravines and the wetlands and lakes. A rarer habitat type,
tallgrass aspen parkland, occurs only in the extreme southeastern corner of the aspen parklands biome (southeastern Manitoba/northwestern Minnesota). The fescue prairie is a meadowland rich in vegetation variety which forms the cover for the development of the richer soils that underlie the parklands. The close association with woodlands and wetlands makes this a choice location for many plants and a preferred range or home site for a wide diversity of wildlife. The richer soil and increased precipitation favours the natural growth of fescue grass, but varying conditions such as moisture level and grazing pressures allow for the invasion of secondary plant species. There are numerous grasses and sedges in the fescue prairie. Gravelly and rocky terrain is a good location for parry oat grass. Dry areas favour June, porcupine and spear grass. Wet areas are often covered with slender wheat grass and timber oat grass. Prairie rose and snowberry are common shrubs found in these grasslands.
Woody plant encroachment is widespread in the parklands. The forested, or woodlands area is dominated by trembling aspen
(Populus tremuloides), balsam poplar
(Populus balsamifera), other poplars and
spruces, although other species of trees including paper birch (
Betula papyrifera) do occur. Pines, mostly
jack pine and
lodgepole pine will often grow in areas that have sandy soil conditions. Other native species may include
box elder,
tamarack and
willow, while the foothills area in the southeast of the region, such as
Turtle Mountain or
Spruce Woods Provincial Park, have woodland of
white spruce and
balsam fir but quaking aspen will dominate where the woodland has been cleared by fire. The proportion of forests to grasslands has increased somewhat over the prairie in areas not affected by agriculture in the last 100 years. This increase is partly due to the reduction of prairie fires which used to destroy the new saplings on the fringes of the aspen groves. Also, it was a common practice for farmers to plant stands of trees as windbreaks. Aspen woodlands support an extensive
understory consisting of mid-sized and small shrubs, some herbs and ground cover. Spruce-dominated woodlands usually do not support a dense understory due to more acidic and nutrient-poor soils and a denser canopy, which reduces sunlight reaching the
forest floor below. However, in areas where a mixture of aspen and spruce occur, a fairly dense understory can still thrive. The mixed wood understory, as it is called, supports the greatest diversity of forest wildlife in the aspen parkland. Large shrubs such as
red-osier dogwood,
beaked willow,
saskatoon,
chokecherry and
pincherry, along with the smaller shrubs including
prickly rose,
snowberry,
beaked hazelnut and
high bush cranberry, form a dense entangled understory. Dense shrubbery is a typical feature in aspen-dominated forests. Common herbs found in the woodlands include:
Lindley's aster (Aster ciliolatus),
northern bedstraw (Galium boreale),
pea vine,
Western Canada violet (Viola canadensis),
dewberry and
bunchberry. Mosses appear at the base of trees and on the ground. Wetlands are very common in this biome, including lakes, shallow open water, marshes, and grassy wetlands. Glacial erosion has contributed to such features by creating depressions in which standing water can collect. In the larger depressions, permanent lakes or ponds of water remain. Many of the lakes have a saline character, thus most shore vegetation has a high tolerance of
salty soils. These lakes are known as
alkali lakes.
Wet meadows are flooded in the spring and dry by fall. They contain
rushes,
sedges and grasses and provide excellent opportunities to study the similarities and differences of these forms of vegetation. Rivers and streams erode valleys throughout the parkland ecoregion. Steep hills and ravines result in a unique topography. Southwest slopes with increased exposure to the sun are dry and often more grass covered, while the shaded north and east exposures retain more moisture and tend to have greater forest cover. Some forms of vegetation unique to the ravines include:
poplar,
spruce,
birch,
willow, and
river alder.
Wildflowers are an important component of the grassland association of the parkland. Look for common
yarrow, cut-leaf
anemone,
rock cress,
creeping white prairie aster,
milk vetch,
late yellow loco weed,
goldenrod,
wild prairie rose,
prairie crocus, and
tiger lily.
Aspen understory There are three main factors which influence the understory vegetation in the aspen stands of the mixed wood forest. 1. Good sun exposure encourages a dense vegetation growth below the canopy. This is of particular importance in the early spring before the trees are in leaf. 2. Warm soil and air temperature at the base level result in rapid melting process in spring which favours the growth of shrubs. 3. A large percentage of precipitation passes through the canopy. This provides a protective snow cover in winter and in warm seasons precipitation percolates through the leaf cover to nourish plants which require surface soil moisture. The result of the above factors is an extensive understory of vegetation in the aspen forest. Common shrubs and herbs are:
saskatoon,
red-osier dogwood,
raspberry,
wild rose,
currants and
bracted honeysuckle,
wild sarsaparilla,
hairy lungwort,
asters, and
peavine.
Twinflower,
strawberries, bunchberries,
horsetails and
wintergreen form an attractive grown cover. The mineral soil is covered by a decaying cover of organic matter. Numerous
consumers and
decomposers create
humus materials. Burrowing animals mix the new fertile materials with the soil to form a rich rooting compound.
Spruce forest understory Factors which influence the understory vegetation of spruce stands in the
boreal forest association include: 1. Year round reduced sun exposure below the canopy restricts the forest undergrowth to shade tolerant species. 2. A large percentage of the precipitation is trapped in the upper tree boughs of the spruce forest and is released through evaporation. The ground cover of
feather moss quickly absorbs most of the moisture which does penetrate the canopy. These factors combine to cause drier conditions in the underlying mineral soils. 3. The fallen
acidic spruce needles are not fully decomposed and combine with the moss base. Water held in the moss carries the acid from the spruce needles into the mineral soil and leaches out soil nutrients – leaving a highly acidic, low nutrient soil base which is unsuitable for most boreal vegetation. As a result of the above factors the
forest floor ranges from nearly devoid of vegetation to a dense carpet of feather moss. A sparse community of shade tolerant shrubs exists in this environment. Some species of plants in the understory are
Green Alder, low bush
cranberry, prickly rose, bunchberry,
twinflower, wild
lily-of-the-valley,
northern Comandra and wintergreens.
Mixedwood stands understory ,
North Dakota There are several factors which influence the
mixedwood stands in the boreal forest. Where there are stands of aspen and spruce forests in close association with each other, a mixed wood forest occurs. Each group forms its own microassociation as described previously. When the spruce and aspen forest types are mixed, the result can be quite different from the aspen or spruce stands. Animal and vegetation associations from each type combine to create considerable diversity of habitat which is typical of either spruce or aspen stands. The mixture of the
transition soils provides an attractive environment with either pure spruce or pure aspen woodlands. An example of a bird which prefers a mixed wood habitat is the
yellow-rumped warbler. The mixedwood forest wetlands consist mainly of
bogs,
fens and marshes.
Black spruce,
tamarack,
willow and bog and
sphagnum mosses are the major vegetation types found in these lowlands.
Dwarf birch and sedges cover large, wet areas with
jack pine occurring on the sandy ridges. For boreal
aspen stands less than 40 years old, Comeau (2002) found that basal area provided a useful general predictor of understorey light levels, but, on the basis of light measurements in one 80-year-old stand, cautioned that relationships between understorey light and basal area may not hold in older stands. The literature indicates that the height growth of understorey spruce should be maximized when light levels exceed 40% or when aspen basal area is less than 14 m2/ha. Models developed by Wright and others in 1998 show radial growth of understorey white spruce increasing almost linearly with increasing light and a continuous decline in radial increment with increasing aspen basal area. When applied to Comeau's 2002 data, the Wright models suggest that spruce mortality will remain very low until aspen basal area exceeds 20 m2/ha, above which mortality will increase rapidly. ==Fauna==