Natural Community Systems -- Photo Guide

Near-boreal minerotrophic swamp system 

a near-boreal minerotrophic peat swamp system at Hurlbert Swamp (photo by Ben Kimball for the NH Natural Heritage Bureau)
a near-boreal minerotrophic peat swamp system 
at Hurlbert Swamp in Stewartstown (photo by Ben Kimball)

This system is primarily found in the North Country on deep, minerotrophic organic soils with Thuja occidentalis (northern white cedar).  At least two swamp types are typically present: northern white cedar - balsam fir swamps tend to occur on organic soils (muck and peat >16 in.); and northern hardwood - black ash - conifer swamps are often found toward the swamp margins on level to sloping mineral soil (shallow organic layer 016 in.).  In contrast to more acidic black spruce peat swamps, this swamp system is strongly influenced by minerotrophic groundwater seepage.  Overall the swamps are conifer-dominated or conifer and mixed hardwood – conifer dominated.  Abundant to frequent northern conifers and hardwoods include northern white cedar, Abies balsamea (balsam fir), Larix laricina (eastern larch), and Picea spp. (spruces); Fraxinus nigra (black ash), Betula alleghaniensis (yellow birch), and Acer rubrum (red maple).  Northern white cedar swamps have a northeastern-boreal distribution in North America (Great Lakes to Canadian Maritimes), and extend into northern New Hampshire, mostly north of the White Mountains.  Black ash is more broadly distributed in eastern North America, but reaches its maximum abundance in New Hampshire in this system.  These are diverse swamp systems that harbor many vascular plants (>200 species) and bryophytes (>65 species), particularly those preferring circumneutral conditions.  The peat and/or muck soils in the northern white cedar - balsam fir swamps are usually over a meter in depth, well decomposed, and with an average pH of 6.1 (range of 4.9–7.5); soils in northern hardwood - black ash - conifer swamps consist of circumneutral to subacid (pH of 5.3–6.3), shallow, well decomposed muck over silty material.  The sloping mineral soil margins can also transition to northern white cedar seepage forest.  There are a few cedar swamps south of the White Mountains, which contain the northern white cedar - hemlock swamp community.  Alder wooded fens are often part of this system, and can mark the transition to open peatland systems or alder alluvial shrublands along large streams.  Calcareous fen openings occur in a few swamps where calcareous groundwater discharge is prominent.

Diagnostic natural communities:

   • Northern white cedar - balsam fir swamp (S2)

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

   • Northern white cedar seepage forest (S2)

   • Alder wooded fen (S3S4)

Peripheral or occasional natural communities:

   • Calcareous sedge - moss fen (S2) 

   • Acidic northern white cedar swamp (S1) 

   • Northern white cedar - hemlock swamp (S2) 

   • Black spruce swamp (S3)

   • Larch - mixed conifer swamp (S3)

   • Northern hardwood seepage forest (S3)

Landscape settings: headwater basins and broad drainageways, extensive flats, pond and lake basins, and adjacent gentle slopes

Soils: deep to moderately deep, well-decomposed peat, grading to mineral soils in sloped swamp margins; moderately to strongly minerotrophic, pHs range from 4.9–7.5; topogenous and soligenous

Spatial pattern: small to large patches (<5–100+ acres), sometimes extensive; circular-oval or irregular shape; uniform or sometimes with sedgy or shrubby openings or surrounding open peatlands

forest to woodland with tall shrub or herbaceous openings

Distribution: occurs north and northwest of the White Mountains; disjunct in Conway area

Characteristic species:
Northern white cedar – balsam fir swamp:
      Thuja occidentalis (northern white cedar)
      Abies balsamea (balsam fir)
      Occasional species:
      Fraxinus nigra (black ash)
      Betula alleghaniensis (yellow birch)
      Acer rubrum (red maple)
      Picea spp. (spruces)

Dwarf shrubs and herbs
      Carex trisperma var. trisperma (three-seeded sedge)
      Osmunda cinnamomea (cinnamon fern)
      Coptis trifolia (goldthread)
      Rubus pubescens (dwarf raspberry)
      Oxalis montana (northern wood sorrel)
      Dalibarda repens (false violet)
      Carex leptalea (delicate sedge)
      Dryopteris cristata (crested wood fern)
      Tiarella cordifolia (foamflower)

      Hylocomium splendens (moss)
      Amblystegium riparium (moss)
      Rhytidiadelphus triquetrus (moss)
      Rhytidiadelphus subpinnatus (moss)
      Thuidium delicatulum (moss)
      Bazzania trilobata (liverwort)
      Rhizomnium punctatum (moss)
      Sphagnum girgensohnii (peat moss)
      Sphagnum subtile (peat moss)
      Sphagnum russowii (peat moss)

Characteristic species largely absent from other cedar swamp communities:
      Mitella nuda (naked miterwort)
      Carex pedunculata (long-stalked sedge)
      Pyrola secunda (one-sided shinleaf)
      Platanthera obtusata (blunt-leaved orchid)
      Rhamnus alnifolia (American alder buckthorn)

Some potential rare species (northern white cedar - balsam fir swamp):
      Petasites frigidus var. palmatus (sweet coltsfoot)
      Carex castanea (chestnut sedge)
      Cypripedium reginae (showy lady's slipper)
      Cypripedium parviflorum var. pubescens (large yellow lady's slipper)
      Cypripedium parviflorum var. makasin (yellow lady's slipper)
      Liparis loeselii (Loesel's twayblade)

Northern hardwood - black ash - conifer swamps:
      Abundant species:
      Fraxinus nigra (black ash)
      Betula alleghaniensis (yellow birch)
      Abies balsamea (balsam fir)
      Picea rubens (red spruce)
      Frequent species:
      Thuja occidentalis (northern white cedar)
      Acer rubrum (red maple)
      Picea glauca (white spruce)
      Populus balsamifera (balsam poplar)
      Fraxinus americana (white ash)

      Alnus incana ssp. rugosa (speckled alder)
      Ilex verticillata (winterberry)
      Viburnum nudum var. cassinoides (witherod)
      Toxicodendron radicans (poison ivy)
      Lonicera canadensis (Canadian honeysuckle)

      Geum rivale (purple avens)
      Onoclea sensibilis (sensitive fern)
      Impatiens capensis (spotted touch-me-not)
      Tiarella cordifolia (foamflower)
      Hydrocotyle americana (water pennywort)
      Senecio schweinitzianus (New England groundsel, Robbins’ ragwort)
      Chrysosplenium americanum (golden saxifrage)
      Carex gynandra (perfect-awned sedge)
      Galium kamtschaticum (northern wild licorice)

      Abundant (particularly the “Brown Mosses” and other non-Sphagnum mosses) but poorly documented

Associated natural community systems: Medium level and rich sloping fens are often associated with this swamp system, and in large wetland basins it may co-occur with near-boreal minerotrophic swamp systems.

[NOTE: This system was formerly named near-boreal minerotrophic peat swamp system]

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