Acidic Sphagnum forest seep
Acidic Sphagnum forest seep (S3S4)
Forest seeps are very small wetlands, typically less than one acre in size, that occur around groundwater discharge areas in upland forests. Species composition varies among sites, but collectively seeps are diverse and support a unique flora and fauna. Despite their small size, seeps add a distinct biological component to the matrix of upland forests. Many herbs, sedges, and mosses are restricted to forest seeps or other seepage wetlands.
Acidic Sphagnum forest seeps are the most acidic seep type, occurring in high and low elevation coniferous forests, on wet outcrops, and along the upper reaches of cool, entrenched streams. They resemble miniature spruce - fir swamps, but always have active seepage that limits peat accumulation. Species composition is variable and characterized by plants both restricted to seepage conditions and not diagnostic of enriched conditions.
Measured pHs do not exceed 5.5. Soils consist of shallow peat or muck layers (<30 cm) over seepy bedrock or, in headwater and streamside positions, over sandy loams.
Characteristic vegetation: Trees that can form a dense, tall shrub or subcanopy layer in this community include red spruce (Picea rubens), black spruce (Picea mariana), and balsam fir (Abies balsamea). The shrub layer is otherwise scant and herbs form a sparse to moderate cover over a dense peat moss (Sphagnum spp.) layer. Characteristic herbs include false hellebore (Veratrum viride), whorled aster (Oclemena acuminata), northern wood sorrel (Oxalis montana), New York fern (Thelypteris noveboracensis), two-seeded sedge (Carex disperma), delicate sedge (Carex leptalea), inflated sedge (Carex intumescens), tall meadow-rue (Thalictrum pubescens), cinnamon fern (Osmunda cinnamomea), goldthread (Coptis trifolia), creeping snowberry (Gaultheria hispidula), field horsetail (Equisetum arvense), northern wild licorice (Galium kamtschaticum) and rough-leaved aster (Aster radula).
This community differs from the subacidic Sphagnum variant of the subacid forest seep community by the absence of foamflower (Tiarella cordifolia), rough sedge (Carex scabrata), and northeastern mannagrass (Glyceria melicaria).
Variants: Two variants are described.
1. Typic variant:
(as described above)
2. Streambank variant:
In contrast to the typic variant, examples along streamsides are influenced by flood- and ice-scour. Additional vegetation may include leatherleaf (Chamaedaphne calyculata), mountain holly (Nemopanthus mucronatus), rhodora (Rhododendron canadense), Bartram's serviceberry (Amelanchier bartramiana), red raspberry (Rubus idaeus), northern arrowwood (Viburnum dentatum var. lucidum), tawny cotton-grass (Eriophorum virginicum), inland sedge (Carex interior), three-seeded sedge (Carex trisperma), few-flowered sedge (Carex pauciflora), contracted sedge (Carex arcta), round-leaved sundew (Drosera rotundifolia), and blue-bead lily (Clintonia borealis).
Good examples occur in the
a small acidic Sphagnum forest seep in the White Mountains (photo by Ben Kimball)
acidic Sphagnum forest seep
(photo by Dan Sperduto)