We undertook a survey of the vegetational ecology of 94 peatlands at Duck Mountain, Manitoba to discriminate differences among peatland types at the southeastern edge of the boreal plain, especially black spruce swamps, and to clarify boreal swamp terminology. The majority of peatlands surveyed were wooded, relatively small (mean = 1.8 ha), and in depressions on the landscape. A classification and indicator species analysis identified the dominant peatland types as moderate-rich fens, with bogs and extreme-rich fens as rare. Black spruce swamps were relatively common and often found on gentle slopes. They were distinguished from wooded fens by larger trees (mean height = 9.7 m; diameter = 12.6 cm), denser overstory (68%), shallower peat depth (90 cm), and small size (1.6 ha). Although most similar to wooded moderate-rich fens by vegetation, black spruce swamps have a denser bryophyte layer and more mesic plant species. Significant indicator species on hummocks and drier areas include Pleurozium schreberi, Hylocomium splendens, Equisetum sylvaticum, Petasites frigidus var. palmatus, Cornus canadensis, Linnaea borealis, Rosa acicularis, Moneses uniflora, Geocaulon lividum, Orthillia secunda, Equisetum arvense, Listera cordata, and Mertensia paniculata. Species characteristically found in black spruce swamp hollows include Rhizomnium pseudopunctatum, Rhizomnium gracile, and Plagiochila porelloides. We discuss conifer swamp terminology globally, and recommend that black spruce swamps be recognized as a peatland type distinct from eastern white cedar-dominated boreal swamps found in the eastern boreal region, wooded fens, and black spruce-dominated uplands. The environmental gradients most strongly associated with an ordination of the Duck Mountain peatland plant community data were forest mensuration variables, e.g., overstory density (range = 7–80%), peat depth (0.4– 3.0 m), peat C:N (14–67), organic C (54–98%), bulk density (0.19–64.00 g/cc), surface-water temperature (3.0–19.5 °C), specific conductivity (0–989 μS/cm), and Ca2 (1.8–111.4 mg/L). Wooded bogs were distinguished from the other peatland types based on mean pH (3.8), alkalinity (0.2 mg/L), Ca2 (5.0 mg/L) and other cations, but there was much overlap among the fens and black spruce swamp. A number of isolated, topographically high, open peatlands were characterized by plant species with affinities to open moderate-rich fens, including Drepanocladus aduncus, Helodium blandowii, Salix discolor, Equisetum fluviatile, and Calamagrostis canadensis, but mean surface water pH (5.4), Ca2 (13 mg/L), DOC (47 mg/L), and NH4 (188 μg/L) were more similar to wooded bogs. This may be the consequence of fluctuating water levels. The potential impact of climate change, in addition to current impacts from logging, emphasizes the importance of understanding the vegetation and environmental variables in southern boreal peatlands.
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Vol. 25 • No. 3