. The Canadian field-naturalist. 342 The Canadian Field-Naturalist Vol. 101 36 were unique to it. The most frequent species were: Calamagrostis stricta (61%), Drepanodadus uncina- tus (55%), Carex glareosa (45%), C. subspathacea (39%), Meesia triquetra (27%) and Aulacomnium palustre (27%). Three species in this list are mosses; a greater proportion of the total vegetation cover was provided by non-vascular species, especially mat- forming mosses, in the second swale (Figure 4). Vegetation associations on the swale were inter- graded. At the seaward edge, where salinities were higher, the veget
. The Canadian field-naturalist. 342 The Canadian Field-Naturalist Vol. 101 36 were unique to it. The most frequent species were: Calamagrostis stricta (61%), Drepanodadus uncina- tus (55%), Carex glareosa (45%), C. subspathacea (39%), Meesia triquetra (27%) and Aulacomnium palustre (27%). Three species in this list are mosses; a greater proportion of the total vegetation cover was provided by non-vascular species, especially mat- forming mosses, in the second swale (Figure 4). Vegetation associations on the swale were inter- graded. At the seaward edge, where salinities were higher, the vegetation was similar to that of the first swale with Puccinellia phryganodes, Carex subspa- thacea, and other species growing in a lawn-like meadow marsh. In the center of the swale, broad Carex glareosa-Drepanodadus and Calamagrostis stricta-Drepanodadus marshes were dissected by occasional small pools supporting patchy growth of Senecio congestus, Hippuris vulgaris or Salix spp. along the margins. The inland end of the swale supported a patchy cover of low-growing Salix brachycarpa, S. glauca, Betulapumila (Swamp-birch) and Juncus balticus, in association with the mosses Calliergon giganteum, Drepanodadus uncinatus and Paludella squarrosa. Discussion The Ridges Hardy species are dominant on the ridges, probably because of the continuous exposure to wind stress and scouring, and moisture stress. On the first ridge, where these conditions were most extreme and the substrate was unstabilized, only clonal growing plants of Honkenya peploides (Figure 5), Elymus mollis, Hedysarum mackenzii and Saxifraga tricuspidata were well established. On the second ridge, with high percentage cover by vegetation (Figure 4) and hence some soil stabilization, more vascular species had colonized. On the third ridge, the temporal sequence had proceeded sufficiently for the establishment of a significant lichen and moss ground cover, and the development, on the backslope, of woody ericaceous and Salix
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