Red spruce swamp (S3)
Red spruce swamps are dominated by red spruce (25-50+% cover) and occur on poorly drained mineral soils with a shallow organic cap. Three-seeded sedge, cinnamon fern, and carpets of peat moss form a lush understory beneath a light to moderate tall shrub layer and a sparse dwarf heath layer. They form in large swamp complexes or lake basins, along small, stagnant drainages, and in pockets or benches on mountain sideslopes, primarily in northern and central parts of the state. Understories are lush, there are light to moderate tall shrub layers, and hummock-hollow topography is slightly to moderately well developed. Soils are acidic, nutrient-poor, and poorly to very poorly drained.
These swamps are slightly more minerotrophic and less saturated than black spruce swamps, as evidenced by the dominance of red spruce, a sparse dwarf heath shrub layer, and mineral soils with a shallow organic horizon. They also appear to be more abundant in the
Soils are acidic, nutrient-poor, and poorly to very poorly drained, with a mineral histic horizon or histic epipedon (usually 10-40 cm deep). Underlying mineral soils range from coarse sand and gravel to finer sand or silts, often derived from ice-contact deposits along drainages, glacial slackwater deposits in broader valley basins, or till sediments.
Characteristic vegetation: The canopies are dominated by red spruce (Picea rubens), with a lush understory of cinnamon fern (Osmunda cinnamomea), three-seeded sedge (Carex trisperma var. trisperma), and carpets of peat moss (Sphagnum spp.). Lesser amounts of balsam fir (Abies balsamea) may occur in the canopy, with occasional black spruce (Picea mariana), red maple (Acer rubrum), and birches (Betula spp.).
Mountain holly (Nemopanthus mucronatus) is a characteristic tall shrub in this community, with lesser amounts of witherod (Viburnum nudum var. cassinoides), winterberry (Ilex verticillata), and speckled alder (Alnus incana ssp. rugosa). Speckled alder may be quite abundant near stream margins or areas influenced by upland runoff (see variants below). Highbush blueberry (Vaccinium corymbosum) is absent from northern examples, though it is present in some central and southern
Herbaceous species are moderately abundant, especially cinnamon fern (<1-40+% cover) and three-seeded sedge (ca. 5-90% cover). Other common species present in lesser abundance (<5% cover) include goldthread (Coptis trifolia), bluebead lily (Clintonia borealis), bunchberry (Cornus canadensis), false violet (Rubus dalibarda), northern wood sorrel (Oxalis montana), northern wild licorice (Galium kamtschaticum), and crested wood fern (Dryopteris cristata). Dwarf raspberry (Rubus pubescens) is an occasional trailing herb. Peat moss (Sphagnum spp.) forms a more or less continuous carpet in hollows and on the sides of hummocks. Species commonly encountered include Sphagnum papillosum, S. magellanicum, and S. fallax. Other mosses are occasional, particularly on hummocks and tree bases. Potential rare plant species of this community include green adder's mouth (Malaxis unifolia), heart-leaved twayblade (Listera cordata), and lily-leaved twayblade (Listera convallarioides).
Variants: Two variants are described:
1. Typic variant: (as described above)
This variant is apparently more acidic and nutrient poor. In general it has a tendency towards greater spruce and fir cover, greater abundance and frequency of cinnamon fern and three-seeded sedge, lower diversity of species, and an absence of minerotrophic herbaceous species indicators (e.g., violets, turtlehead, rein-orchids, and “brown mosses”).
2. Red spruce - hardwood - violet variant:
This variant usually has the same species as the typic variant, but also a greater prominence of hardwood trees, a greater diversity of herbs, and greater influence of upland runoff or seepage. Trees may include yellow birch (Betula alleghaniensis), red maple (Acer rubrum), paper birch (Betula papyrifera), and gray birch (Betula populifolia). Cinnamon fern and three-seeded sedge are usually still present, but in lesser abundance.
Species richness appears to be greater than in the typic variant, perhaps indicative of more minerotrophic conditions or greater light availability. Species indicative of this type include northern white violet (Viola macloskeyi) and other violets (Viola spp.), white turtlehead (Chelone glabra), small green woodland orchid (Platanthera clavellata), tall white bog orchid (Platanthera dilatata), and false hellebore (Veratrum viride).
Sphagnum is usually abundant or dominant in the moss layer. Peat depth is generally shallow, although some examples appear to have depths exceeding one meter. This variant is similar to the northern hardwood - black ash - conifer swamp community, but generally lacks black ash and numerous other species indicative of more minerotrophic conditions.
Good examples of this community occur at
Red spruce swamps often occur as part of lowland spruce - fir forest/swamp systems, and sometimes as part of black spruce peat swamp systems and temperate peat swamp systems.
Red spruce swamp at Annett State Forest (photo by Pete Bowman)
edge of a dense red spruce swamp near Elbow Pond
(photo by Ben Kimball)