Boundaries

This ecoregion spans much of the province of Saskatchewan and is bounded by the Churchill River drainage up to, but not including, Reindeer Lake to the north, and the South Saskatchewan, Qu’Appelle and Assiniboine river drainages to the south.

Topography

This ecoregion has little gradation with flat-lying Paleozoic limestone bedrock covered with glacial till, silts, clays, and peat deposits. Cretaceous shale with shallow depressions has caused a large number of small, shallow glacial pothole lakes, ponds, and sloughs to form.

Freshwater habitats

This ecoregion lies on the Canadian Shield and has been covered by glaciers as recently as 10,000 to 15,000 years ago. Consequently, the area has many oligotrophic lakes and clear, cold streams. The Churchill River has rapids, falls, narrow chutes, and many long stretches of slow-moving water. There is also lacustrine habitat, as the river has a chain of interconnected lakes. The Saskatchewan, Qu’Appelle, and Assiniboine rivers form deep, wide valleys in the prairie and carry a heavy load of silt, traveling through rich farmland.

Terrestrial habitats

This ecoregion grades from coniferous forests in the north to grasslands in the south. Dominant species in the north include quaking aspen (Populus tremuloides), balsam poplar (P. balsamifera), and bur oak (Quercus macrocarpa), with an understory of mixed herbs and tall shrubs. White spruce (Picea glauca) and balsam fir (Abies balsamea) are present in areas unaffected by fires, and jack pine (Pinus banksiana) occurs on drier, sandy sites. Wet areas have sedges (Carex spp.), willow (Salix spp.), black spruce (P. mariana), and tamarack (Larix laricina). Grasslands are usually a mixture of tallgrass and shortgrass prairies, and include grama (Bouteloua gracilis), little bluestem (Schizachrium scoparium), needle-and-thread grass (Stipa comata), western wheatgrass (Agropyron smithii), threadleaf sedge (Carex filifolia), and junegrass (Koelaria cristata). The northern short grasslands have spear grass (Poa annua), blue grama grass, wheatgrass, and dryland sedge (Carex spp.). Shrubs, such as sagebrush (Artemesia tridentata), are common.

Description of endemic fishes

The ecoregion contains no known endemic species.

Ecological phenomena

Historically, the lake sturgeon (Acipenser fulvescens) likely undertook long spawning migrations. Many of the aquatic organisms found in this ecoregion are adapted to widely fluctuating aquatic environments, from flash floods to drought.

Justification for delineation

The ecoregions of Canada were identified based on the faunal similarity of 166 major watersheds based on a cluster analysis of freshwater fish occurrences in these watersheds. The Middle Saskatchewan ecoregion is comprised of watersheds in the middle of the Canadian prairies. This fish fauna is similar to the fauna of the Upper Saskatchewan [107] ecoregion, except that it lacks any foothill species and has several more eastern species as a result of its closer proximity to the Mississippian refugium.

Level of taxonomic exploration

Good / Fair