. The Canadian field-naturalist. 1975 Jeglum: Peatland - Vegetation Changes After Damming 401 is no mean annual water deficiency. Mean daily temperatures for July and January are 63°F (°C) and 0°F ( —°C), respectively (Chapman and Thomas 1968). The study area occurs where Highway 11 crosses a peatland valley, approximately V^ mile ( km) wide, which lies between two parallel ridges (Figures 1-3). The highway, built in 1938, has obstructed natural drainage. One side of the road has been flooded and the treed vegetation previously found there re- placed by an open, spongy or floating,
. The Canadian field-naturalist. 1975 Jeglum: Peatland - Vegetation Changes After Damming 401 is no mean annual water deficiency. Mean daily temperatures for July and January are 63°F (°C) and 0°F ( —°C), respectively (Chapman and Thomas 1968). The study area occurs where Highway 11 crosses a peatland valley, approximately V^ mile ( km) wide, which lies between two parallel ridges (Figures 1-3). The highway, built in 1938, has obstructed natural drainage. One side of the road has been flooded and the treed vegetation previously found there re- placed by an open, spongy or floating, Sphag- /7w/7z-dominated mat. Methods Two transects were established across the peatland, one on either side of the highway, approximately parallel to and 50 m from the cleared margins of the highway (Figures 2 and 3). Quadrats, 2 X 2 m, were placed at 10-m intervals along each side of the transects, 43 on the treed side and 25 on the open side. Ocular estimates of percentage canopy cover were made for all species. Nonvascular species not known in the field were collected for later identification only if they attained at least 25% cover in the quadrat. Nomenclature for vascular species is according to Gleason and Cronquist (1963), that for Sphagna is according to Nyholm (1969). Quadrats were classified as one of three main peatland formations — bog, fen, or swamp (cf. Zoltai et al. 1974). "Bog" is defined as a nu- trient-poor ecosystem that is Sphagnum-rich, underlain by a relatively continuous horizon of Sphagnum peat, and is relatively isolated from any influx of mineral soil-influenced waters. In this study we did not use the strict definition of bog as equivalent to ombrotrophic (Sjors 1961, 1963)—nourished only by nutrients contained in precipitation; rather, we preferred a slightly broader construct which includes minerotrophic, transitional bogs with ombro- trophic bogs. Quadrats were further character- ized according to dominant species in tree, tall
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