Natural Community Systems -- Photo Guide

Forest seep/seepage forest system

forest seep at St. Gaudens Natl. Historic Site (photo by Ben Kimball for the NH Natural Heritage Bureau)
forest seep/seepage forest system at St. Gaudens Natl. Historic Site.
 note: this system usually covers a larger area than shown in this photo (photo by Ben Kimball) 


Description:  This is a broadly defined, spatially small wetland system that corresponds to forest seeps; seepage runs along headwater streamlets, and to their somewhat larger counterparts of northern New Hampshire, seepage forests.  These tend to be small, isolated, sloping seepage wetlands up to about 5 acres in size, with most examples being much smaller (<0.25 ac).  While small, they are distinct from their surrounding upland forests.  Soils are saturated to seasonally saturated, poorly to very poorly drained and have a shallow muck layer over silty or loamy (occasionally sandy) materials.  pHs range from the mid 5s to over 7.  They have some floristic similarities to other minerotrophic swamp systems, but they have a more limited set of vascular plants in any given example, and are more variable from one seep to another.  They are well demarcated, however, by a set of seepage and other minerotrophic plants that, as a group, primarily occur in seeps. Seepage forest examples are found primarily in northern New Hampshire; examples further south tend to be small patch forest seeps.  Black ash (Fraxinus nigra) dominated swamps (black ash variant of northern hardwood – black ash – conifer swamp) occur on shallow but distinctly sloping silty soils at slope-bases and around swamp margins.

Diagnostic natural communities:

• Subacid forest seep (S3S4)

• Acidic Sphagnum forest seep (S3S4)

• Circumneutral hardwood forest seep (S3)

• Northern hardwood seepage forest (S3)

• Northern hardwood – black ash – conifer swamp (S2)

Landscape settings: groundwater discharge points and zones in upland forests; bases of steep slopes; slopes where slowly-pervious soil layers force groundwater to the surface

Soils: usually silty or loamy, sometimes sandy, with a shallow muck layer; poorly to very poorly drained non-riparian; moderately to strongly minerotrophic, subacid to circumneutral (mid 5s to >7); soligenous and topogenous

Spatial pattern: small patches, points, or narrow-linear zones perpendicular (e.g., slope-bases) or parallel to flow direction such as seepage runs (0.1 – 10+ acres); uniform zonation or sometimes with multiple, parallel seepage runs

Physiognomy: forest or woodland tree canopy, usually sparse to moderate shrub layer, and very dense herb and bryoid layer

Distribution: broad distribution in the state, but more common and larger examples found in northern New Hampshire

Characteristic species:
Seepage indicators:
Tiarella cordifolia (foamflower)
      Carex scabrata (rough sedge)
      Glyceria melicaria (northeastern manna-grass)
      Circaea alpina (small enchanter’s nightshade)
      Aster puniceus (purple-stemmed aster)
      Chrysosplenium americanum (golden saxifrage)
      Platanthera dilatata (tall white bog orchid)
      Galium kamtschaticum (northern wild licorice)
      Geum rivale (purple avens)
      Mitella diphylla (two-leaved miterwort)
      Listera cordata (heart-leaved twayblade)
Listera convallarioides (lily-leaved twayblade)
      Cardamine pensylvanica (Pennsylvania bitter-cress)
      Chelone glabra (white turtlehead)
      Hydrocotyle americana (water pennywort)
      Veratrum viride (false hellebore)
      Carex leptalea (delicate sedge)
      Carex disperma (two-seeded sedge)
      Equisetum sylvaticum (wood horsetail)
      Cypripedium pubescens (large yellow lady's-slipper)
      Cystopteris bulbifera (bulblet bladder fern)
      Sphagnum squarrosum and other bryophytes

Associated natural community systems:  This system is most often embedded within upland forests, although they occasionally occur at the border of various other wetland types.

forest seep/seepage forest system in the White Mountains (photo by Ben Kimball)
forest seep/seepage forest system
 in the White Mountains (photo by Ben Kimball)

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