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Thompson-Pavilion

thompsonpavillion

Grassland Region

Area, ha

Ecoprovince

Thompson-Pavilion

143,975

Southern Interior

Ecosections

Area, ha

Thompson Basin

Pavilion Ranges

98,840

38,175




The Grassland Landscape

Thompson-Pavilion grasslands region is dominated by the large, deep, steep-sided valleys of the Thompson, North Thompson, Bonaparte and Fraser Rivers. Grasslands are extensive in the valley bottoms and lower slopes and interlace with the dry ponderosa pine and Douglas-fir forests at higher elevations. They are most extensive in the Thompson River valley and tributaries, Hat Creek valley and along the Fraser River north of Lillooet.

The present landscape was sculpted by a 1000 metre thick ice sheet that covered the interior plateaus 15,000 years ago. As the ice melted about 12,000 years ago, vast quantities of water flowed over the area, over-deepening river valleys, filling many valleys with temporary lakes and depositing thick layers of glacial till and silts.

Valley floors are lake-bottom flat and upland areas consist of flat terraces and gullies often interspersed with rocky cliffs and talus slopes. Winds blew a layer of fine sands and silts over the landscape that in places provided a favourable substrate for the creation of soils.

thompsonpavillion1In the rainshadow of the Coast Mountains, rainfall is lowest in the western portions of the region, increasing towards Chase and up the North Thompson River. Hot dry air flows into the region from the south during the summer while the region is often under the influence of Arctic air masses in winter. The large expanse of grasslands around Ashcroft, at the junction of the Bonaparte and Thompson Rivers, are as dry as those found in the South Okanagan. At Cornwall Hill, grasslands extend from the valley floor on south-facing slopes almost to sub-alpine elevations over only 15 kilometres.

Research studies in the Lac du Bois area northwest of Kamloops, where south-facing slopes gradually rise up to the heights of the plateau, have demonstrated the effect of elevation on temperature and precipitation. Precipitation increases from 240 millimetres in the valley bottom to 300 millimetres above 850 metres while temperatures are warmer and frost-free periods are longer in the valley bottom.

Historical Impacts

Most of the accessible lower elevation grasslands have been heavily used over the past 150 years as the livestock industry developed and thrived. In and around urbanized areas grasslands have been lost to development.

Local First Nations had horses by the turn of the eighteenth century and by the 1870s were trading them to the Hudson’s Bay Company. The Company relied on horses to transport furs from trading posts to coastal ports, with as many as 750 head overwintering in the Lac du Bois grasslands by 1855. The gold rush brought more people into the area and livestock numbers, including cattle, sheep and oxen increased substantially.

thompsonpavillion2Overgrazing was recognized as a concern by 1873, but it was not until the 1930s that steps were taken to try to restore the grasslands. Better range management was introduced, but significant improvements were not found in the grasslands until recent years. Fencing of pastures and systems of rotational grazing allow native species to recover gradually.

Conversion of grasslands to forage crops was attempted between 1870 and 1920 and at Lac du Bois dry land wheat farming was attempted. 2000 hectares of grassland at Walhachin was converted to orchards. All these enterprises eventually failed and the land is slowly reverting to native grassland. More recently, large areas of valley bottom grasslands converted to hayfields have been used for growing ginseng.

Unique Features 

The grasslands developed on the gently rising landscape northeast of Kamloops with its south-facing aspect represent the range of grasslands found in British Columbia. The Lower, Middle and Upper Grasslands can be visited within 16 kilometres of the Thompson River valley bottom. Nowhere else in the province, or indeed, in western North America, are they found in such close proximity.

The Lac du Bois area has been the centre of grasslands research since 1928 when Agriculture Canada responded to ranchers’ concerns about cattle diseases and opened the Livestock Insects Laboratory. The present research facility was established in 1947 and an area of the Lac du Bois Grasslands and adjacent open forests was established as a site for research.

Fenced exclosures can be found throughout the grasslands in the area, the oldest established as early as the 1930s. They provide important baselines for studying such issues as changes in grasslands vegetation, plants poisonous to livestock, grasshopper control and weed management.

As part of their research efforts to re-establish plant communities on the large areas of bare ground in the Lac du Bois area, pieces of sod were brought in from other places, including out of province, to follow their progress in establishing a plant cover.

The meadows that line the hillsides north east of Chase are among the most unique in the province. From mid-late April glacier lilies and spring beauty bloom in phases from the lowest elevations up to the forest edge. They are followed by an abundance of flowering plants that include silky lupine, Columbia bladderpod and silverleaf phacelia found further south in the Okanagan valley and Southern Thompson Upland. In drier areas bluebunch wheatgrass is the dominant species, and Idaho fescue is found at its most northerly distribution.

Plant Communities

Ecosections

BEC Zones with grasslands1

Major2 grassland BEC Subzones and Variants

Thompson Basin

Bunchgrass Zone

Ponderosa Pine Zone

Interior Douglas-Fir Zone

BGxh2: Thompson Very Dry Hot Bunchgrass Variant

BGxw1: Nicola Very Dry Warm Bunchgrass Variant

PPxh2: Thompson Very Dry Hot Ponderosa Pine Variant

IDFxh2: Thompson Very Dry Hot Interior Douglas-fir Variant

IDFdk1: Thompson Dry Cool Interior Douglas-fir Variant

Pavilion Ranges

Bunchgrass Zone

Ponderosa Pine Zone

Interior Douglas-Fir Zone

BGxh2: Nicola Very Dry Warm Bunchgrass Variant

BGxh3: Nicola Very Dry Warm Bunchgrass Variant

PPxh2: Thompson Very Dry Hot Ponderosa Pine Variant

IDFxh2: Thompson Very Dry Hot Interior Douglas-fir Variant

IDFdk1: Thompson Dry Cool Interior Douglas-fir Variant

1. Click here to find out more about the Biogeoclimatic Ecosystems Classification(BEC) System

2. Over 3,000 hectares

Over 98% of the grasslands in Thompson-Pavilion region are found in the Bunchgrass, Ponderosa Pine and Interior Douglas-Fir zones, in only four variants.

Grasslands in the Thompson-Pavilion region are protected in parks and other conservation areas where livestock grazing is managed to reduce the impact on plant communities. Research projects are giving grasslands managers a better understanding of grasslands species and their particular needs.

BGxh2: Thompson Very Dry Hot Bunchgrass Variant: 45,560 hectares

Known as the Lower Grasslands, these grasslands are found in the Thompson valley from Spences Bridge to Prichard up to about 700 metres elevation. Long, hot summers and low annual rainfall that falls mostly as winter snow produces a mix of plants adapted to this harsh environment. They account for almost 33% of the region’s grasslands.

thompsonpavillion3Widely spaced clumps of bluebunch wheatgrass, big sagebrush, and an array of early spring blooming plants are characteristic. Flowering plants include common rabbit-brush, brittle prickly-pear cactus, sagebrush buttercup, yellow bell, large-fruited desert parsley, and Thompson’s paintbrush. Interspersed between the plants is a thin, fragile layer of lichens, mosses and fungi called a cryptogamic crust that helps to protect the soil from erosion.

Areas of rough fescue can occur on cooler north-facing slopes with round-leaved alumroot, parsnip-flowered buckwheat, saskatoon and common snowberry. Common rabbit-brush, Sandberg’s bluegrass, big sagebrush, and low pussytoes are common in disturbed areas. Cheatgrass, Russian thistle, diffuse knapweed, Dalmation toadflax and leafy spurge are only a few of the non-native species also found in disturbed areas.

BGxw1: Nicola Very Dry Warm Bunchgrass Variant: 29,580 hectares

thompsonpavillion4Middle Grasslands occur above the Lower Grasslands to about 1000 metres, from Kamloops to Pritchard, in the Lac du Bois grasslands, and at Elephant and Rattlesnake Hills north of Ashcroft. A cooler, moister climate results in a denser cover of plants, fewer sagebrush and more flowering plants. Bluebunch wheatgrass is the dominant grass, with Sandberg’s bluegrass common. Characteristic flowering plants include thread-leaved fleabane, mariposa lily and yarrow with arrow-leaved balsamroot on some sites. Giant wild rye is found on moist seepage sites.

Non-native species such as Japanese brome, cheatgrass, common dandelion, diffuse knapweed, spotted knapweed, Dalmatian toadflax have invaded disturbed areas.

PPxh2: Thompson Very Dry Hot Ponderosa Pine Variant: 22,010 hectares

Ponderosa pine forests are usually found from 400 to 950 metres between the Bunchgrass and Interior Douglas-fir zones. They occur as narrow bands along the Fraser River between Lytton and Lillooet, the Yalakom River to Bridge River and above the Thompson, North Thompson and Nicola Rivers.

Open stands of trees are interspersed with grasslands and only occasional shrubs such as big sagebrush, rose and saskatoon. The grasslands usually reflect those found immediately adjacent to the forest and may range from Lower to Upper grasslands.

Bluebunch wheatgrass occurs in the driest sites and rough fescue is found more frequently in moister sites. On open, drier sites bluebunch wheatgrass, Sandberg’s bluegrass, junegrass, yarrow, and lemonweed are found but on the very driest sites big sagebrush and compact selaginella dominate with small amounts of rough fescue, junegrass, yarrow and Sandberg’s bluegrass.

thompsonpavillion5In some areas these grasslands, such as the Dewdrop range west of Tranquille River, were heavily grazed by large herds of horses in the late 1800s. Bluebunch wheatgrass and rough fescue have been replaced with needle-and-thread grass, junegrass and Sandberg’s bluegrass and non-native weeds are present in overgrazed areas.

The mountain pine beetle epidemic of 2005-07 has killed over 70% of the ponderosa pine trees in this variant and the impact this will have on the grasslands is not known.

IDFxh2: Thompson Very Dry Hot Interior Douglas-fir Variant: 25,220 hectares

Cooler temperatures and more precipitation in both summer and winter results in lush grasslands with many wildflowers in the Upper Grasslands and parklands of this Variant. They occur from 850 to 1130 metres, above the Ponderosa Pine and Bunchgrass zones both north and south of Kamloops, and at the north end of Hat Creek valley.

Rough fescue is the dominant grass in the Upper Grasslands along with bluebunch wheatgrass, Columbia needlegrass, Kentucky bluegrass, and Junegrass. Arrow-leaved balsamroot occurs in waves in some areas, and chocolate lily, upland larkspur, sticky geranium, yarrow, death camas and parsnip-flowered buckwheat are common. There are few shrubs in this grassland and there is no microbiotic layer between the closely-growing plants.

thompsonpavillion6Bluebunch wheatgrass is found on dry sites along with prairie sagewort, junegrass, needle-and-thread grass and umber pussytoes. As much as 95% of the vegetative cover on some sites may be rough fescue as few species can compete with it, or with the thick litter layer. 

Many areas of the Upper Grasslands have been altered by long time grazing with needle-and-thread grass, low pussytoes and yarrow as common species, along with many non-native species such as dandelion, Russian thistle and cheatgrass. In recent years these non-native plants have been displaced by noxious weeds such as spotted knapweed, common hound’s tongue and Dalmatian toadflax. Improvements in cattle management over the past 30 years are helping the restoration of these grasslands.

IDFdk1: Thompson Dry Cool Interior Douglas-fir Variant: 5,885 hectares

thompsonpavillion7

This variant, a continuation of the Upper Grasslands, occurs between about 1130 and 1460 metres and covers large areas west of Cache Creek and northeast of Paul Lake near Kamloops. In other areas they occur as openings on cool, moist sites in an otherwise continuous forest.
The dominant grasses are rough fescue and bluebunch wheatgrass, with spreading needlegrass, yarrow and junegrass commonly associated with them. On drier sites bluebunch wheatgrass and june grass are dominant and dense stands of trembling aspen are found in moister sites.

Overgrazing has also altered these grasslands with many areas of exposed soil and noxious weeds such as spotted knapweed and Dalmatian toadflax.

Other Grassland Communities

Small areas of grasslands are found in the Montane Spruce Zone between 1320 and 1650 metres in the western part of the region near Lillooet and west of Ashcroft. Little is known about the range of communities in this zone, but bluebunch wheatgrass is often found to be the dominant grass in several communities, along with junegrass and white pussytoes on some sites.

Where grasslands occur amongst Douglas-fir, pinegrass may be present with a shrub layer containing tall Oregon grape and common snowberry. Pinegrass also forms the dominant species at higher elevations in this zone, along with a diverse layer of flowering plants. Grasslands are also found in many of the other BEC zones in the region but only in small, discontinuous patches.

The complex landscape of this region includes rocky outcrops, talus slopes and gullies where hot, dry conditions take grasslands into forested areas, while cool, moist exposures encourage trees growth down into the grasslands. On cool, moister north-facing slopes throughout the grasslands Douglas-fir patches add diversity to the landscape.

Lakes and ponds are notably absent over much of the grasslands in Thompson-Pavilion although a variety of wetland types occur in depressions and gullies. Cattail and bulrush marshes, Baltic rush communities and willow swamps are only a few of the plant associations found. Water levels rise with spring run-off and many are dry by summer’s end. Saline ponds occur in many areas where water levels rise with spring run-off but evaporate quickly in the heat of summer. Salt-adapted plants occur as rings of vegetation around the ponds, with maritime or red glasswort creating a striking red rim against the white salt-encrusted centre.

Trembling aspens grow in the moister sites and north-facing slopes throughout the grasslands and are particularly extensive on cooler, moist sites in the Upper Grasslands. Patches of rose and snowberry add to the variety of the landscape and the complex of habitats in the Upper Grasslands. Cottonwoods stands line river edges in the Thompson River valley, often with trembling aspen, paper birch and a mixed shrub layer.

Key Plant Species

thompsonpavillion8Sagebrush buttercup (Ranunculus glaberrimus)

  • One of the earliest flowering plants at all elevations,
  • pushes through the snowy ground on warm lower slopes in early March
  • several stems from 5 – 15 centimetres long
  • elliptical rounded leaves at the base and divided leaves on the stem
  • the only buttercup to have both types of leaves
  • bright, shiny, yellow flowers with five petals may cover large patches of ground
  • many tiny seeds are produced on each flower
  • plants are dried up and disappeared by early summer on lower slopes, later at higher elevations
  • a poisonous plant, First Nations used the poison on arrowheads
  • “ranunculus” means “little frog, while “glaberrimus” refers to the “smoothest” leaves.

Wildlife

The rich variety of habitats found in the Thompson-Pavilion region are home to a wide range of wildlife. Many species move between the grasslands and open forests for their needs during the year. Some species found here are at the northern limit of their distribution in the province.

A variety of reptiles and amphibians are found throughout the lower and middle grasslands including the spotted frog, common garter snake, Western garter snake and long-toed salamander. In the hotter and drier lower grasslands and ponderosa pine forests, gopher snake, Western rattlesnake, rubber boa and racer are present in small numbers. Western toad, spotted frog and long-toed salamander are found in the forested variants in the region.

About 180 species of birds use the grasslands and dry forests of the Thompson-Pavilion region. Ground-nesting birds include long-billed curlew, meadowlark and vesper sparrow, while killdeer and common nighthawk nest directly on the ground. Mountain bluebird, American kestrel, raptors and owls rely on the grasslands for many of their needs, while nesting on the forest edges.

thompsonpavillion9The ponds, lakes and wetlands are filled in spring with migrating waterfowl, many of which move to higher elevations or more northern latitudes for breeding. Mallard, American widgeon, lesser scaup, redhead, ruddy duck, Barrow’s goldeneye and northern shoveler are only a few species known to breed. Marshy edges are home to blackbirds, marsh wrens and rails.
Aspen groves, riparian areas and the grassland-forest edge with their rich insect populations provide important habitat for a variety of songbirds, finches, thrushes and sparrows. Owls and woodpeckers also take advantage of these rich areas.

Mule deer are found throughout the region, where they spend the winter in the open forests above the grasslands and use the grasslands in early spring as soon as young grass shoots begin to sprout. A small group of Rocky Mountain elk were introduced in the lower Thompson River valley west of Lytton where they use lower grasslands in spring, fall and winter.

Coyotes are found throughout the lower elevation grasslands in Thompson-Pavilion Region and red fox are found in the Lac du Bois area. River edges, ponds, lakes and wetlands provide habitat for river otter, beaver and muskrat. The pocket gopher is found only south of the Thompson River, at the northern limit of it range, while a number of mice, voles and shrews are found throughout the grasslands.

Check the list of wildlife viewing sites publications.

Species at Risk

Red- and Blue-listed grassland elements in the Thompson-Pavilion:

Element

Red List*

Blue List**

Vascular Plants

Plant Communities

Insects

Reptiles and Amphibians

Birds

Mammals

Total Elements

37

18

0

0

3

1

59

18

7

0

5

8

4

42

*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.



Only a few of the listed species in Thompson Pavilion grasslands region, including low hawksbeard, rough dropseed and satin grass, are unique to the region. Oregon checker-mallow is found in the Middle and Upper Grasslands in Lac du Bois Grasslands Protected Area and nowhere else in Canada. Some species found in lower elevations also occur in the Okanagan valley, such as Okanogan Fameflower, while others also occur in the East Kootenay Trench region.

More than 70% of the twenty-five red-and blue-listed plant communities in the Bunchgrass, Ponderosa Pine and Interior Douglas-fir zones are considered to be endangered.

Blue-listed reptiles, including western rattlesnake, gopher snake, racer and rubber boa, are found in the lower elevations of the bunchgrass and Ponderosa pine zones. The rocky south-facing slopes above Kamloops Lake are particularly favoured by the western rattlesnake. The blue-listed Great Basin spadefoot toad occurs around ponds in the Lower Grasslands.

Of the eleven listed bird species, the red-listed western screech owl, and prairie falcon have only been recorded incidentally while the burrowing owl was recorded only once in the 1930s. All of the blue-listed species are found in the lower elevations of the Thompson Basin.

Great blue heron are found at lakes, ponds and wetlands throughout the lower elevations of the region, but only a few nesting colonies are recorded. White-throated swifts nest on steep cliffs and canyons and feed on flying insects. They are known to occur at Marble Canyon Provincial Park and on cliffs in Kamloops.

Sharp-tailed grouse nest in lower elevation grasslands moving up into the dry forests. Numbers have declined since the 1960s and known leks and habitat are protected in Lac du Bois Grasslands protected Area. Long-billed curlew also nests on the ground, preferring open areas with short plant cover.

Lewis’s woodpeckers are found in the lower elevation cottonwoods stands and open ponderosa pine forest where they nest in trees and feed on insects, fruits and seeds. Loss of cottonwoods stands is of particular concern for this species.
California bighorn sheep were introduced on the north slopes of Kamloops Lake in the 1960s and now range as far east as Monte Creek. They use the lower elevation grasslands in spring, fall and winter, moving into the cooler forests for summer grazing.

Tranquille Wildlife Management Area is an important resting area during migration for many waterfowl and other birds, including the red-listed Western Grebe and American Pelican.

A Species at Risk Profile: Gopher Snake (Pituophis catenifer deserticola)

thompsonpavillion10Blue-listed in BC

The hot, dry grasslands of the Thompson-Pavilion region are home to the Gopher Snake. The back and sides of this one-to two-metres long gopher snake have black or brown blotches in rows similar to the Western rattlesnake. However, the small head and dark stripe across the head from one round eye to the other distinguish the gopher snake’s head from the triangular shape of the rattlesnake’s large head. The gopher snake in not venomous and has no rattle at the end of its tail, although it can take a defensive stance, when its tail vibrates.

In spring and fall it forages during the day but as the summer heat increases it becomes more nocturnal. The preferred habitats are shrub grasslands beside ponds where it feeds on gophers, mice, squirrels and even small rabbits. Eggs are laid in a rock crevice, under a talus slope or in a burrow in early July and young hatch in late August or early September. It hibernates deep in the rocks of south-facing slopes.

Habitat for gopher snakes has been reduced by urban development, by ploughing of grasslands for agriculture, by recreational activity and by destruction of den sites. Gopher snakes are often mistaken for rattlesnakes and killed.

In the Thompson-Pavilion region the gopher snake is at the northern limits of its range which coincides with the northern limits of big sagebrush in the Thompson and Fraser valleys.

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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