Contributions to the flora of the Red Lake Peatland, northern Minnesota, with special attention to Carex

The Red Lake Peatland, situated in N-central Minnesota, is the largest continuous mire in the northern portion of the contiguous United States. It consists of a mixture of ombrotrophic bogs and minerotrophic fens organized into a complex of highly distinctive landforms, including open bogs, wooded bogs, Sphagnum lawns, strings, flarks, fen-pools and wooded islands. The bogs are poor in species and occupy acid sites with water poor in mineral salts; the minerotrophic areas are floristically richer and can be divided into poorand rich-fen sites. Ditching and roadbuilding in certain portions of the peatland have produced drastic changes in the vegetation and landscape as a result of obstructed water tracks flooding upstream and drying out downstream. The peatland, which occupies a large area of gentle slope and poor drainage, has a flora that is relatively impoverished. In all, 331 plant taxa were recorded from the mire, including 195 vascular plants, 67 bryophytes and 69 lichen taxa. Members of the Cyperaceae account for 23 % of the vascular flora, and the largest genus in the mire is Carex with 29 species. Each landform feature is distinctive in its floristic composition, and the vascular and nonvascular taxa associated with the different physiographic features are discussed. This paper provides an account of Carex in the peatland and discusses the differential response by members of the genus to gradients of nutrition, shading and hydrology. Some carices grow best under acid conditions, thus frequenting ombrotrophic and poor-fen sites, whereas other species grow best in rich-fen sites. Carex species useful in separating areas of ombrotrophy from those of poor fen are indicated, as are those carices that serve as obligate rich-fen indicators. The floristic similarities between the Red Lake Peatland and 14 other peatlands in North America and northern Europe are discussed, and the ombrotrophic bog flora of the Red Lake Peatland is compared to the bog floras of the Hudson Bay lowlands and northern Fennoscandia.