East Kootenay Trench
East Kootenay Trench
Southern Interior Mountains
East Kootenay Trench
The Grassland Landscape
Grasslands in the East Kootenay Trench grassland region extend from the Canada/US border north to Radium, but are most extensive just north of the border and in the prairies between Cranbrook and Skookumchuck. The southern grasslands are an extension of much more extensive grasslands in Montana
Grasslands extend from the trench into the large valleys that join the trench, including the Elk, Bull, Wigwam in the south and the Kootenay and Findlay. The northern limit of grasslands is in the Sinclair River valley at Radium Hot Springs and of ponderosa pine and associated grasslands at approximately the Columbia Lake lookout on Highway 93.
This long, narrow, trench is situated between the high mountains of the Purcells on the west and the Rockies on the east. It varies from 24 kilometres wide in the south to 3 kilometres at the narrowest and owes its present landforms to the last glaciation. As the ice sheet wasted away leaving isolated blocks of ice in the valley, a 130 kilometre long lake was created where deep silts were deposited. Later erosion and deposition by the rivers entering the valley has created the present landscape of terraces, gullies, channels and the two large lakes, Columbia and Windermere. Extensive wetlands along the Columbia River cover the valley bottom north of Columbia Lake.
Arctic air masses from the north contribute to the cold winter temperatures while hot, dry air from the south brings high summer temperatures. Weather systems from the west are intercepted by the Purcell Mountains and leave the trench in a rainshadow. Rainfall ranges from 355 millimetres at Cranbrook to 390 millimetres at Radium Hot Springs and Windermere is the driest part of the valley at 280 millimetres.
Soils have developed on limestone rich glacial deposits that contain large amounts of calcium.
Historical Land Impacts
Many factors have influenced the development of grasslands in the East Kootenay Trench including climate, fire, forest expansion, logging, grazing by livestock and wildlife, and settlement.
While lightning is the only natural cause of fires, aboriginal people used fire to maintain open grasslands and to feed their growing number of horses. Logging and expansion of settlement in the early years of the twentieth century came with more fires, many of them traveling far beyond their intended extent.
The grasslands have also been altered by long time grazing by often large herds of horses and other livestock. In the 1880s there were as many as 2,000 horses and 500 head of cattle on Joseph’s Prairie in the Cranbrook area. More domestic animals were added as the Canadian Pacific railway expanded into the area and more settlers arrived.
Feral horses were a particular problem even into the 1960s. As livestock numbers declined in more recent years the populations of mule deer and elk have increased substantially. The grasslands continue to be in a largely overgrazed condition. The historic alteration of the native grasslands in the trench mean that scientists are not able to describe the original grasslands.
Unique Features - Dutch Creek Hoodoos
Highway 93 takes a sharp right hand turn over Dutch Creek, at the north end of Columbia Lake. The turn in the road follows the huge serrated wall of silts called the Hoodoos. This wall is only the southernmost end of the long southern edge of a high, flat bench that runs along the west side of the Trench above the Columbia River. Extensive grasslands cover the bench, with Douglas-fir forests on cooler slopes and aspens filling the gullies
The bench is apparently older than the last glaciation having been deposited into some long ago lake. Mixed layers of silts and coarser material indicate the differences in the material being brought into the lake by an ancient river. Thousands of years of erosion has sculpted the distinctive hoodoo pillars and the cap of coarser materials on the upper layers has helped to protect them.
BEC zones with Grasslands
Major2 grassland BEC Subzones and Variants
|East Kootenay Trench
Ponderosa Pine Zone
Interior Douglas-Fir Zone
Montane Spruce Zone
Engelmann Spruce-Sub-alpine Fir Zone
PPdh2: Kootenay Dry Hot Ponderosa Pine Variant
IDFunn: Undifferentiated Nelson Forest Region Interior Douglas-fir Variant
IDFdm2: Kootenay Dry Mild Interior Douglas-fir Variant
1. Click here to find out more about the Biogeoclimatic Ecosystems Classification(BEC) System
2. Over 3,000 hectares
The lowest parts of the East Kootenay Trench are at 700 metres which is 300 metres higher in elevation than the lowest areas in the Okanagan grasslands region. 90% of the grasslands are found in the Ponderosa Pine and Douglas-fir zones, with only small pockets in the Montane Spruce and higher elevation zones.
Some species commonly found in the south Okanagan and Kettle River grasslands are less common in the East Kootenay Trench. Antelope-brush is widespread on the Kootenay River floodplains and occurs on dry sites from the Tobacco Plains to just south of Canal Flats.
Bluebunch wheatgrass, Idaho fescue, rough fescue, mock orange and bitterroot are all found in the southern part of the trench, but only Idaho fescue and rough fescue extend as far north as Invermere. Brittle prickly-pear cactus, common in the south Okanagan, is only found in a few places in the Trench. Big sagebrush is found in a small patch near Invermere and as individual plants in the far south, while common rabbit-brush and arrow-leaved balsamroot are uncommon.
PPdh2: Kootenay Dry Hot Ponderosa Pine Variant: 15,900 hectares
These grasslands extend north from the Canada/Us border as large and small areas through the Tobacco Plains and from the lower St. Mary River valley as far as Skookumchuck. They were much more extensive in the south before Lake Kookanusa was created behind the Libby dam on the Kootenay River. The original community is thought to have been similar to the Upper Grasslands of the Thompson Basin.
Ponderosa pine occurs up to 950 metres elevation as far north as Canal Flats, where it mixes with Douglas-fir. Under the best conditions there is a mix of grasses including Idaho fescue, rough fescue and bluebunch wheatgrass with silky lupine, timber milk-vetch, round-leaved alumroot and meadow death-camas among other flowering plants.
An area at Skookumchuck Prairie that was enclosed with a fence in the 1950s to keep livestock out has been monitored to follow the change in plant cover without grazing. After 50 years of study Idaho fescue seems to be the dominant species.
IDFunn: Undifferentiated Nelson Forest Region Interior Douglas-fir Variant: 3,500 hectares
The original plant species of this variant are unknown as the area has been heavily overgrazed and along Columbia Lake has been converted to agricultural land. It is likely that rough fescue, Idaho fescue and bluebunch wheatgrass dominated the community with a few Douglas-fir trees. Common rabbit-brush, Rocky Mountain juniper, common juniper and saskatoon would also have been present.
IDFdm2: Kootenay Dry Mild Interior Douglas-fir Variant: 23,450 hectares
This variant occurs above the ponderosa pine variant in the south and from the valley bottom to 1200 metres as far north as Briscoe. It is only found in the driest sites and ponderosa pine and Douglas-fir trees make up less than 15% of the cover.
On the warmest sites antelope-brush and other shrubs including chokecherry, saskatoon, and mock-orange grow under open Douglas-fir stands. North of Canal Flats Rocky Mountain juniper is the dominant shrub. Other grassland communities in these open Douglas-fir forests are dominated by bluebunch wheatgrass.
Other Grassland Communities
A 20 to 30 hectare area of grassland east of Golden on a steep slope above the Kicking Horse River is the most northerly extent of this plant community in the Trench and the most easterly extent of grasslands in the province.
Small pockets of grasslands and open forests occur on south and east-facing slopes in the Montane Spruce Zone. Grasslands are also found into the alpine where there are rich arrays of flowering plants.
Cottonwood forests are found on the active floodplains along the Kootenay River, Lake Kookanusa and Lake Windermere. Black spruce, red-osier dogwood, Nootka rose, prickly rose and mountain alder are common accompanying species. Ponds, marshes and wetlands occur on the upland benches where many of them dry up during the summer months. The presence of alkali saltgrass and foxtail barley indicate the highly alkaline conditions of many ponds.
Marshes are found from the valley bottom to the Montane Spruce Zone with bulrushes the most common species. Where cattail marshes do occur they are often the only plant in the marsh.
Shrublands commonly develop after fires and are widespread in the grasslands of the trench. The species composition varies with location with antelope brush the dominant species south of Canal Flats and below 1150 metres. At higher elevations and further north in the valley snowbrush, redstem ceanothus and soopolallie are the most common species.
Trembling aspen often grows up after fires and is also found in moist depressions and swales throughout the Trench.
Key Plant Species
- Found throughout the grasslands of the Trench as far north as Invermere
- on cool, north-facing slopes but less frequent in open forest grasslands
- perennial bunchgrass that grows in a dense tufted, from 30 – 90 cm tall
- leaves are long and narrow with a blueish colour and are very rough to the touch
- an important grass for grazing livestock, but reduced in abundance by heavy grazing.
The complex mix of grasslands, open forests and closed forests, combined with the extensive wetlands of the Columbia and Kootenay rivers provides habitat for a wide variety of wildlife species. Many use the adjacent grasslands for at least parts of their life cycle.
The common garter snake, western garter snake, western toad and long-toed salamander are the only reptiles and amphibians commonly found in the Trench.
Over 70% of the birds found in BC occur in this region and over 60% of species that breed in the province can be found here. Typical grassland species include western meadowlark, vesper sparrow, that nest in the shelter of large bunchgrass plants, and common nighthawk, that lays its eggs directly on the ground. Brewer’s blackbird, black-billed magpie and bank swallow are some other commonly seen birds.
Raptors, such as the turkey vulture, Cooper’s hawk, American kestrel and bald eagle, find prey in the open grasslands but nest away from the grasslands in large trees or cliffs.
The Black-chinned hummingbird, black-billed cuckoo, common poorwill and western bluebird are all found in the Trench but are less-commonly found in other grassland areas of the province. The white-breasted nuthatch is found in open pine and fir grasslands forests and has the highest number of breeding pairs in the province. While most grassland birds migrate south in the fall, Clark’s nutcracker, Bohemian waxwing, Harris’s sparrow are only a few of the birds that remain for the winter, foraging and sheltering in the open forests.
Wetlands, ponds and marshes and adjacent riparian vegetation are home for a wide variety of birds including ducks, geese, shorebirds and perching birds. Many species use the area to rest during migration but killdeer, American coot , Mallard, red-winged blackbird, marsh wren and a host of warblers stay to nest and raise their young.
A variety of small mammals are found in the grasslands including the yellow-bellied marmot, Columbian ground squirrel, mice, voles and shrews. The coyote is an efficient predator.
The East Kootenay trench has the largest populations of Rocky Mountain elk, mule deer and white-tailed deer in the province. They forage in the lower elevation grasslands in spring and rely on the Montane Spruce grasslands in fall and early winter. The open forests are important for thermal cover in winter.
Click here for a list of wildlife viewing sites publications.
Species at Risk
Red- and Blue-listed grassland elements in the East Kootenay:
Reptiles and Amphibians
*Red list: List of ecological communities, and indigenous species and subspecies that are extirpated, endangered or threatened in British Columbia.
**Blue list: List of ecological communities, and indigenous species and subspecies of special concern (formerly vulnerable) in British Columbia.
Most listed plant species occur in the Kootenay Dry Mild Interior Douglas-fir variant, and all but one of the red-listed species (Flat-topped broomrape) occur there. Some species including yellow buckwheat, androsace buckwheat, elk thistle and fuzzy-tongued penstemon are unique to the east Kootenay Trench grassland region.
Annual paintbrush, three-spot mariposa lily and viviparous fescue are not as abundant in other parts of the province. Yellow buckwheat and three-spot mariposa lily are apparently near their northern limit in BC. Some listed species, such as prairie crocus, prairie coneflower scarlet gaura and scarlet globe-mallow and others are of prairie origin.
Three butterfly species are red-listed, the Dione copper, Gillette checkerspot and the vivid dancer and two are blue-listed: the common ringlet and the eastern tailed blue. Painted turtle and rubber boa are the only two listed reptiles found in the region, occurring in wetlands in the ponderosa pine and Douglas-fir grasslands.
Only one red-listed bird species recorded in the Trench is confirmed as nesting there: the American avocet, an elegant shorebird, relies on small grasslands ponds and marshes. The grasshopper sparrow may occur in the extreme southern end of the Trench. The red-listed peregrine falcon, anatum subspecies and prairie falcon have been observed during the nesting season but their status is not confirmed. They hunt over grasslands, open forests and wetlands but nest elsewhere.
The blue-listed great blue heron and the American bittern can also be found in wet areas; the heron nests in colonies, usually in cottonwood trees while the secretive bittern builds a well-concealed nest over the water in cattails or rushes. Sandhill cranes prefer isolated marshes and wet areas in forest openings for breeding, and are known to nest in the Trench north of Cranbrook.
The flammulated owl in open Douglas-fir forests breeds as far north as Radium Hot Springs. Lewis’s woodpecker relies on ponderosa pine, black cottonwood or Douglas-fir snags for nesting and forages over adjacent grasslands for flying insects. Found in the open grasslands and forests from the Ponderosa Pine to the Montane Spruce Zone, they are known to nest at Newgate, Wycliffe and Windermere.
Long-billed curlew prefer well-grazed grasslands with low vegetation and are found from Grasmere to Windermere. Sharp-tailed grouse are present in the southern portion of the Trench, although their numbers are uncertain. The bobolink, a black and white bird the size of a meadowlark, is found in open grasslands and open forests from the Ponderosa Pine Zone to the Montane Spruce Zone.
White-throated swift is recorded from the northern end of the East Kootenay Trench grasslands Region, where it would be nesting on steep cliffs.
Red-listed badger and blue-listed ermine are the only small mammals at risk in the Trench.
Blue-listed Rocky Mountain bighorn sheep forage in the grasslands year-round and use nearby cliffs and talus slopes for lambing and escape terrain. They also use Montane Spruce forests for fall and early winter grazing and are sometimes found on ridges in the sub-alpine and alpine areas. Important habitat areas are along the east side of Columbia Lake and the west-facing slopes on the east side of Lake Windermere.
A Species at Risk Profile: Long-billed curlew
Blue-listed in BC
Listed under the Federal Species at Risk Act (SARA)
The largest concentration of Long-billed curlew nesting pairs in East Kootenay Trench grasslands region is at Skookumchuck Flats where at least twenty breeding pairs have been recorded.
Long-billed curlews prefer short grass areas, presumably so they can for see predators more easily. Where there are large numbers they will nest fairly close together. They feed on beetles and grasshoppers during the breeding season in BC. Nests are made in small depressions which they line with some grass and usually lay four eggs. Their streaky brown colouring allows them to blend in with the dead leaves from the previous year’s plant growth.
Once hatched, the birds move their chicks to longer grass usually in moister sites or even hayfields. Only one or two chicks survive the attention of the raptors, owls, crows, ravens and magpies that prey on them. Curlews have left the grasslands by the end of August and moved to coastal or inland mudflats from California to Guatemala.
The population in the Trench seems to be increasing but there is the ever-present threat of habitat loss due to conversion of grassland to other uses and encroachment of trees into their grasslands habitat.
For more information on species at risk in BC, visit our SAR page.
For definitions of technical terms, please see the GLOSSARY.
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