Mixed Grass Prairie in Manitoba
A vast expanse of grassland once stretched across the Canadian prairie provinces. Short-grass prairie, the most drought tolerant, was found in the rainshadow of the Rockies. In the moisture rich Red River Valley of Manitoba, a sea of grasses and wildflowers grew in the tall-grass prairie. Mixed grass prairie lay between the two prairie types, blending elements of both short-grass and tall-grass prairie. Here, the wildflowers and grasses grew to knee height and huge herds of bison roamed the plains.
The beauty and resilience of the mixed-grass prairie lies in its incredible diversity of species. There are over 150 species of plants, each adapted in its own way to the extremes of temperature, variations in precipitation and the effects of fire and grazing. Local topography, the nature of the soil, and year-to-year changes in moisture and temperature help determine the mix of plants found in each prairie. In areas with well drained soils, drought tolerant grasses such as western wheatgrass and blue grama often prevail, but within metres, little bluestem, a grass requiring more moisture, will dominate.
All animals, from voles and ground squirrels to large grazers like bison, play a role in the development and composition of a prairie. Any disturbed ground - along an animal trail, beside a burrow or in a bison wallow - can encourage annual plants that complete their life cycles in one season to sprout and hold the soil until the longer living grasses and perennial wildflowers establish themselves.
Numerous combinations of moisture, topography, soil and disturbance exist making every prairie unique and dynamic in its species and appearance. In Manitoba, mixed grass prairie occurs in areas receiving between 250 mm and 500 mm (10"-20") of precipitation annually. Its occurrence is often determined by the presence of soils that are sandy or well-drained. Remnants of mixed grass prairies are usually found intermingled with aspen stands or other grassland communities.
Mixed grass prairie and many of its plants and animals have been and continue to be lost. As early as the 1860s, settlers were having dramatic, long term effects on the prairies. By the 1880s plains bison, plains wolves and passenger pigeons had been eliminated and many other species were diminishing rapidly. The prairie itself was being lost as homesteaders broke the sod to grow crops. The introduction of exotic or weed species, such as leafy spurge and Canada thistle, encroachment by native shrubs and trees, and overgrazing by livestock have led to the degradation of thousands more hectares. Originally there were approximately 24 million hectares (59 million acres) of mixed grass prairie in Canada. Today, less than one quarter of this remains. To identify the remaining parcels of native prairie, the Critical Wildlife Habitat Program is conducting an inventory of the mixed grass prairie in southwestern Manitoba.
Endangered and Threatened Species
Manitoba's Endangered Species Act (1990) protects plant and animal species that are considered endangered or threatened within Manitoba. Under the Act, native species threatened with extinction are classified as "endangered". Native species likely to become endangered or found in low numbers are classified as "threatened". A species is considered "vulnerable" if it is found in low numbers or restricted areas but is not yet threatened. Vulnerable species are not protected under the Act. The following mixed grass prairie species are recognized and protected as endangered or threatened in Manitoba.
lady's slipper(Cypripedium candidum)
The small white lady's slipper is an endangered orchid found in wet meadows in fewer than 10 locations in southern Manitoba. It grows in clumps, blooming briefly in late May or early June. It is unlawful to pick, dig or disturb the surroundings of this plant.
Baird's Sparrow (Ammodramus
The Baird's sparrow is well camouflaged to blend into its prairie environment, but its call, two to three zips followed by a musical trill, is distinctive. It nests on the ground in idle or lightly grazed native mixed grass prairie. Formerly common throughout southern Manitoba, they are now restricted to the southwest corner of the province.
Burrowing Owl (Athene
The burrowing owl prefers grazed pastures or mixed grass prairie. Unlike any other North American owl, it nests below ground, occupying abandoned ground-squirrel (gopher) burrows. In Manitoba, the known nesting population had dwindled to four pairs by 1995. The loss of nesting habitat and poisoning of owls by insecticides intended to control grasshoppers have contributed to their decline.
Loggerhead Shrike (Lanius
The loggerhead shrike lives primarily in open shrubby country and dry upland prairie. It is known for its practice of impaling its food (grasshoppers, insects or rodents) on thorns and barbed wire. Loss of grasslands and shrublands, combined with the accumulation of pesticides in the food chain, are the main reasons for their decline.
Hawk (Buteo regalis)
The largest hawk in North America, it is often seen soaring above the open grasslands searching for ground-squirrels. Ferruginous hawks usually nest in isolated trees, building large flat nests. Recent population increases have resulted in the status of this species being changed from threatened to vulnerable.
Plants of the Mixed grass Prairie
Prairie plants are perfectly adapted to their environment. Many have extensive root systems for absorbing moisture and nutrients from the soil during periods of low moisture. Some plants, known as cool-season species, begin their growth early, taking advantage of the spring moisture before becoming dormant in the heat of the summer. With the advance of fall and cooler temperatures, these plants renew their growth and replenish their food reserves before the onset of winter. Other plants, called warm-season species, have adapted to the hot summers and low moisture levels by changing the way they produce food in their leaves and stems. Their unique metabolism allows them to grow during hot, dry weather without losing precious moisture.
At first glance, a mixed grass prairie may look like a field of unmown grass, but a closer look reveals the complexities and subtle enchantment of this prairie world. Some of the typical wildflowers and grasses you may find when you visit mixed-grass prairie are illustrated here.
crocus (Anemone patens)
A sign of spring in North American prairies and Manitoba's floral emblem, the crocus often blooms shortly after the snow disappears. Its many-divided, silky leaves arise after flowering is completed.
Spear grass (Stipa comata)
The slender, pointed fruits of spear grass have long, twisted "beards" or awns projecting from their tips. After the seed is shed, the first moisture causes the awn to straighten. Then, in drying out, the awn twists again and screws the seed of this cool season grass into the soil, where it can germinate.
Indian breadroot (Psoralea esculenta)
Indian breadroot has a thick, tuberous root once valued as a food source by Aboriginals and early settlers. As this plant is very sensitive to disturbance, the presence of Indian breadroot usually indicates a healthy prairie.
Dotted blazing star (Liatris punctata)
Dotted blazing star was once used by Aboriginals to treat kidney diseases and has long been cultivated in gardens as a bedding plant and for cut flowers.
Blue grama (Bouteloua gracilis)
Blue grama grass is easily recognized by its seed head which resembles a toothbrush. This warm season grass is very drought hardy and will out compete taller grasses in times of low moisture.
Purple coneflower (Echinacea angustifolia)
The roots of the purple coneflower were used by Aboriginals as a painkiller for toothaches and sore throats.
The natural forces of fire and grazing helped shape and form mixed grass prairie. The extensive root reserves of native prairie plants allow them to regrow quickly after grazing or burning occurs. In order to maintain good quality native mixed grass prairie, rotational grazing and occasional controlled burning must continue to be used. Excessive grazing can eliminate or suppress many species. However, the absence of grazing can increase woody growth and lead to a build up of plant litter, choking out some native species. Haying or mowing can also decrease woody species when burning or grazing are not possible. It is recommended that haying or mowing be done after mid-July, when ground nesting birds have left their nests.
How often a prairie should be burned depends on the purpose of the burn and local moisture conditions. Properly timed burns can help decrease woody growth and the presence of weedy species without long-term detrimental effects. However, annual burns on mixed-grass prairie can be destructive over the long term, lowering moisture levels and destroying organic matter in the soil. Each prairie should be treated individually, according to the plant species present and the surrounding land use.
Why Save It?
The reasons to save native mixed grass prairie are many and varied. It is home to a wide variety of plants and animals, some that are commonplace and others that are rare. Species like sharp-tailed grouse and deer are frequently observed but some, such as small white lady's slippers and burrowing owls, are seen only by a lucky few. Native prairies and the species in them are often useful, economically and scientifically. No one knows what value prairie species may hold for future crops, medicines and other products. Native mixed-grass prairie is a living museum brimming with beauty and untapped information, a rich natural heritage for all Manitobans.