Threatened dry grasslands in the continental boreal forests of Wood Buffalo National Park

Abstract

Dry grasslands in Wood Buffalo National Park are unique biological features at 60°N latitude, since they contain plant species normally found in more southern grasslands at 50–55°N latitude. The objectives of this study were to inventory dry grasslands, classify them according to similarity of species cover, and establish relationships with understory species in Populus tremuloides and shrub communities. Dry grasslands were studied at nine sites; most were clustered in the Salt River and Peace Point areas. The largest unit of grassland was about 3.0 ha, and most units were less than 0.5 ha. This contrasts with the hundreds of hectares recorded earlier in the century. Of the 128 vascular plant species identified, 29 are considered as southern, and of these, 15 are regionally rare. Sixty-four plots were classified into nine community types, using two-way indicator species analysis. A group of six communities were dominated by grass and shrub species with a component of southern grassland species. Three communities, strongly dominated by Populus and shrubs, represent community types that invade dry grasslands. Ordination of plots using detrended correspondence analysis showed relationships among the community types and a clear separation of southern grassland species from those found in forest communities. Vascular plant diversity, as represented by mean species richness, ranged from about 15 to 28, and Shannon diversity indices ranged from 1.883 to 2.615. The cover of southern grassland species was negatively correlated (correlation coefficient of −0.524) with cover of tall shrubs and trees, suggesting that the dry grasslands of Wood Buffalo National Park are threatened by tree and shrub invasion, which is due, in part, to a lack of recent fires at these sites. Key words: northern grasslands, biodiversity, endangered species, endangered spaces.