Natural Community Systems -- Photo Guide

Poor level fen/bog system

poor level fen/bog system at Red Hill Pond(photo by Dan Sperduto for the NH Natural Heritage Bureau)
poor level fen/bog system at Red Hill Pond (photo by Dan Sperduto)

poor level fen/bog system at Pondicherry Wildlife Refuge (photo by Ben Kimball for the NH Natural Heritage Bureau)
 poor level fen/bog system at Pondicherry Wildlife Refuge (photo by Ben Kimball)



DescriptionPoor level fen/bogs are open, extremely acidic peatlands with only a limited amount of minerotrophic influence from the surrounding uplands, and very little or no groundwater or lake and stream influence.  Oligotrophic to weakly minerotrophic conditions prevail, with pHs ranging from the high 3s to low 4s.  They occur in a variety of landscape settings, ranging from nearly closed-basins to broad drainageways with sluggish, meandering streams, and adjacent to lakes but away from the influence of the lake-water.  They are most frequent in areas of glacial outwash or ice-contact deposits.  Peat is generally quite deep and poorly decomposed in the upper layers, with a well-developed hummock - hollow topography.
Most of the peatland area is dominated by species indicative of oligotrophic to, at most, weakly minerotrophic conditions including scattered, stunted black spruce, and extensive areas of mostly dwarfed heath shrubs (<0.5 m; leatherleaf, small cranberry, sheep laurel, bog laurel). 

A typical community sequence from the upland border towards the center of the peatland is a tall shrub fen or black spruce swamp border, followed by a dense leatherleaf - black spruce bog zone, then a reddish open moss carpet (Sphagnum rubellum) with extremely dwarfed shrubs, and occasionally patches of Sphagnum pools or lawns with Sphagnum cuspidatum or other aquatic peat mosses.  There is sometimes a wet moat or lagg separating the peat mat from the surrounding upland.  This develops from a combination of elevated nutrient levels in upland runoff and the periodic seasonal draw-down of the water table that increases the decomposition of the peat mat at the peatland margin.  If a moat is not present, the outer zone is usually dominated by a peat swamp or a tall shrub fen (most commonly highbush blueberry - mountain holly wooded fen).  With the exception of the zone immediately along the upland border, pHs are usually in the low 4s or lower throughout the peatland.  Floristic differences are evident in northern or higher elevation examples compared to coastal or southern examples, but the overall vegetation patterns are similar.

Diagnostic natural communities:

      • Sphagnum rubellum - small cranberry moss carpet (S3)

      • Leatherleaf - black spruce bog (S3)

      • Leatherleaf - sheep laurel shrub bog (S1S3)

      • Highbush blueberry - mountain holly wooded fen (S3S4)

Peripheral or occasional natural communities:

      • Large cranberry - short sedge moss lawn (S3) 

      • Marshy moat (S4))

      • Water willow - Sphagnum fen (S3)

Landscape settings: closed or stagnant, open headwater basins with limited drainage, often in depressions in glacial outwash or ice-contact deposits or broad lake basins away from the influence of lake water

Soils: deep, poorly decomposed peat oligotrophic, pHs generally <4.1; topogenous (limited limnogenous and soligenous influence)

Spatial pattern: small to large patch (5100+ acres), occasionally extensive; circular to irregular shaped; more or less concentric zonation, less often irregular zonation; often with outlet stream, but without inlet streams

Physiognomy: sparse woodland, tall shrub, dwarf shrub, moss carpets/lawns

Distribution: broadly distributed; largest examples in central and northern New Hampshire

Characteristic species:
Dwarf to short shrubs
      Chamaedaphne calyculata (leatherleaf) -- <20” high (max 36”)
      Kalmia angustifolia (sheep laurel)
      Kalmia polifolia (bog laurel)
      Andromeda polifolia var. glaucophylla (bog rosemary)
      Ledum groenlandicum (Labrador tea)
      Vaccinium oxycoccos (small cranberry)
      Gaylussacia baccata (black huckleberry)
      Gaylussacia dumosa (dwarf huckleberry)

Herbs and carnivorous plants
      Drosera rotundifolia (round-leaved sundew)
      Drosera intermedia (spatulate-leaved sundew)
      Sarracenia purpurea (pitcherplant)
      Eriophorum virginicum (tawny cotton-grass)
      Eriophorum vaginatum (hare's-tail)
      Carex trisperma var. billingsii (Billing's sedge)

Trees and tall shrubs (sparse and dwarfed)
      Vaccinium corymbosum (highbush blueberry)
      Picea mariana (black spruce)

pHs generally 4.1 or lower
Refer also kettle hole bog system for list of minerotrophic indicators absent from poor level fen/bog systems.

Associated natural community systems This system can co-occur in large peatland basins with medium level fen and peat swamp systems (e.g., black spruce, coastal conifer, or temperate peat swamps).  It is common for poor level fen/bogs to have small marginal areas adjacent to water bodies or uplands that have more minerotrophic communities typical of medium fens.  When these areas are limited in extent or constitute a small proportion of the peatland, they are considered inclusions within the poor level fen/bog; when they are more extensive or constitute a substantial proportion of the peatland, the peatland may best be treated as having both poor and medium level fens systems within the same wetland.  Conversely, medium level fens can have areas with more limited minerotrophic influence with poor fen communities.  These are treated in the same way.

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