A Reconsideration of Grassland Classification in the Northern Great Plains of North America

One climax community of Fescue Prairie and five climax and edaphic climax communities of Mixed Prairie are characterized on the basis of studies in ninety-six relatively undisturbed sites over an 18-year period in the glaciated, Canadian Great Plains. This classification represents modifications from one proposed a decade ago on the basis of response of communities to more favourable growing conditions from 1950 to 1956. The relative dominance of species is judged on the basis of calculated foliage yield. The communities are: A. Festuca scabrella Association of black soil. B. Mixed Prairie 1. Stipa-Agropyron Faciation of medium-textured soils in the dark-brown and moist portion of the brown soil zones. 2. Stipa-Bouteloua-Agropyron Faciation of medium-textured soils in the arid portion of the brown soil zone. 3. Stipa-Bouteloua Faciation, an edaphic community of well stabilized sandy soils. 4. Bouteloua-Agropyron Faciation, an edaphic climax in the more arid areas where Cretaceous shale has modified the drift. 5. Agropyron-Koeleria Faciation, an edaphic climax on fine-textured lacustrine soils. The nature of these grassland communities is similar to those which have been described in adjacent areas of the United States south of the glacial boundary. The more xeric types of Canada extend southward, while the mesic types do not. Primary and secondary plant successions towards the climax and edaphic climax communities are described.