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, variation in precipitation and the effects of fire and grazing animals. Local topography, the nature of the soil, and year-to-year changes in moisture and temperature help determine the mix of plants found in a particular prairie. In areas with well drained soils, drought tolerant grasses such as western wheatgrass and blue grama may grow, 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 plants that complete their life cycles in one season, to sprout, holding the soil until the longer living grasses and 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 25 cm and 50 cm (10"-20") of precipitation annually. Its occurrence is also determined by the presence of soils that are sandy or well-drained. Remnants of mixed-grass prairies are often found inter-mingled with aspen stands and other grassland communities.
Mixed-grass prairie and many of its plants and animals have been and continue to be lost. As early as the 1860's, settlers were having dramatic long term effects on the prairies. By the 1880's plains bison, plains wolves and passenger pigeons had been eliminated and many other plants and animals 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, and the invasion of native shrubs and trees, led to the degradation of thousands of hectares more. It is estimated that there were originally 24 million hectares of mixed-grass prairie in Canada. Today it covers less than one quarter of that area.
PLANTS OF THE MIXED-GRASS PRAIRIE
Prairie plants are perfectly adapted to their environment. Many have extensive roots systems that are ideal for absorbing moisture and nutrients from the soil during periods of low moisture. These root reserves are important for regrowth after grazing or burning. Some plants, cool-season plants, begin their growth early in the season to take advantage of the early spring moisture and stop growth in the heat of the summer. Other plants called warm-season plants 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, mixed-grass prairie may simply 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.
THREATENED AND ENDANGERED SPECIES IN MIXED-GRASS PRAIRIE
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.
The natural forces of fire and grazing helped shape and form mixed-grass prairie. The extensive root reserves of native 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.
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. 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 prairies are many and varied. It is home to 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 the small white lady's slipper and burrowing owl, 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.
NatureNorth.com would like to thank the Critical Wildlife Habitat Program and the Wildlife Branch, Manitoba Natural Resources for permission to reproduce this "Manitoba's Mixed Grass Prairie" brochure.
Thanks for learning about Manitoba's Mixed-grass Prairie! Bye for now!
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