GRASSLAND OF THE PEACE RIVER REGION, WESTERN CANADA

Abstract

Natural grassland is associated with poplar and willow groves to form parkland areas on dark soils in the generally forested Peace River region of western Canada. The grassland is described as an Agropyron–Stipa–Carex community. Comprising this community are three subtypes or faciations, viz. Agropyron–Carex on low areas, Stipa on dry slopes, and Agropyron–Stipa on mesic sites. For the entire community 154 vascular species are recorded and for the Agropyron–Stipa faciation, which is the most common native grassland of the region, 139 vascular species, consisting of 36 graminoids, 84 forbs, and 19 woody species. The leading grasses are Agropyron trachycaulum, Stipa spartea var. curtiseta, and Koeleria cristata. The Agropyron–Stipa faciation is the "climax" grassland of the region and therefore may be classified as an "association". The occurrence of native grassland areas in the boreal forest region is explained in terms of special physiographic and edaphic features of these areas, notably poorly drained and inadequately aerated soils. Therefore, the Agropyron–Stipa grassland may be interpreted as an edaphic climax. Compared with the fescue grassland of south-central Alberta, the Peace River grassland lacks Festuca scabrella but has many of the other plants of the fescue association, certain of these assuming the role of leading species. Reliable indicators of early stages in grassland retrogression brought about by heavy grazing are the small sedges, Carex obtusata and C. heliophila.