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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.
Small white
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
bairdii)
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
cunicularia)
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
ludovicanus)
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.
 Ferruginous
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.
Prairie
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.
Management
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.
Photo credits: Marilyn Latta, Dennis Fast, Critical Wildlife
Habitat Program
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