In the South Saskatchewan River Sub-Basin (SSRSB), plant species include native and non-native, or invasive plants. The plants can generally be divided into woody and non-woody plants. Invasive plant species are spreading widely throughout the area.


Note: Reach SS-02 is from the confluence of the Oldman and Bow Rivers (where they join to form the South Saskatchewan River), to the Medicine Hat gauging station. Reach SS-01 is from Medicine Hat gauging station to the Alberta / Saskatchewan border.

Cottonwood trees (Cottonwood Poplar) trees are found in both reaches along the South Saskatchewan River, and at one site Manitoba maples (Acer Negundo) were present. The Manitoba maple is a native species to North America, but it is considered invasive since it colonizes quickly whether or not the area is cultivated. About 63% of the project area was covered with preferred trees. There is moderate to heavy grazing pressure from livestock, and to a lesser degree, from wildlife in the area.

The regeneration of trees is very good at all but two sites where their levels of regeneration were considered low to moderate. Successful regeneration of the woody plants maintains and promotes riparian health. The number of dead trees is normal to moderate in the area.


In Reach SS-02, the main woody plant species is plain cottonwood. About 28% of the area is covered with shrubs, and 16% of the area is covered with trees. The regeneration of cottonwoods and preferred trees is poor to absent. Invasive cover 66% of the area. The reason for the poor occupation by native species, (which are less than 5%), is unknown.


In Reach SS-01, the number of trees and shrubs are twice as many as in SS-02. About 57% of this area is covered with shrubs and 29% with trees. Regeneration of trees and shrubs, cottonwoods and preferred trees, in most of the areas in SS-01 is quite good but some areas are poor or moderate.


Trees in the Aspen Parkland Region

Alberta has four forest regions, each with its own variety of trees and unique climate. The regions are the Boreal, Aspen Parkland, Subalpine and Montane. Refer to the map below to see the different qualities of each region. The South Saskatchewan River Sub-Basin primarily includes the Aspen Parkland region.

Aspen Parkland Region

The Aspen Parkland region is situated between the northern Boreal forest and the southeastern grasslands. It is the most densely populated forest region in Alberta; its numerous wetlands make it a popular breeding area for ducks. The climate in the Aspen Parkland region is typically very warm in the summer, and very cold in the winter. Tree species include:

Read more… about the global evolution and role of trees (