Natural Community Systems -- Photo Guide

Emergent marsh - shrub swamp system

emergent marsh - shrub swamp system in an oxbow of the Blackwater River (photo by Ben Kimball for the NH Natural Heritage Bureau)
an emergent marsh - shrub swamp system in an
oxbow of the Blackwater River (photo by Ben Kimball)

an emergent marsh - shrub swamp system at Great Meadow along the Exeter River (photo by Ben Kimball)
an emergent marsh - shrub swamp system
at Great Meadow along the Exeter River (photo by Ben Kimball)

Description:  This system occurs on well-decomposed muck and mineral soils along small, low-gradient, seasonally flooded streams (mostly first- and second-order) and in open basins with outlet streams.  Soils consist of sandy and silty mineral materials and/or well decomposed muck (often shallow organics over mineral soil).  Most examples exhibit a broad flood regime gradient from permanently flooded or intermittently exposed to seasonally flooded conditions.  Corresponding natural communities include aquatic beds, emergent marshes, meadow marshes, alluvial shrub thickets, and seasonally flooded swamps.  Periodic beaver activity sets successional states back towards deeper water communities (pond, aquatic beds, or emergent marsh), while beaver dam abandonment and subsequent pond drainage shifts the successional track back towards meadow marsh and more wooded states.  Some abandoned beaver meadows consist of sedge meadow marshes characterized by minerotrophic peat mosses and marsh herbs on well decomposed muck and often with standing snags indicative of raised water levels.  These peaty marshes likely succeed to shrub or swamp states with continued drainage.  Medium fen communities are occasionally associated with this system, particularly along sluggish drainages or in inlets away from the influence of streams.  Emergent marsh and aquatic bed communities in this system also occur along lower energy sections of rivers and major streams (see also low gradient silty-sandy riverbank system), ponds, and lakes.  There is considerable variation among examples of this system in terms of diversity of communities, flood regimes, and successional states present, but there is relatively little geographic variation across the state.  Community composition is influenced to some extent by stream and soil characteristics (i.e., mineral vs. organic soils) and geography, although many of the natural communities in this system have wide geographic ranges.  Most of the variation among examples relates to diversity of flood regime conditions and effects of beaver activity on community composition.

Diagnostic natural communities:

   Emergent marshes and aquatic beds

      • Tall graminoid meadow marsh (S4)

      • Sedge meadow marsh (S4)

      • Short graminoid - forb meadow marsh/mudflat (S4)

      • Emergent marsh (S5)
      • Cattail marsh (S4)

      • Aquatic bed (S4S5)

      • Herbaceous seepage marsh (S3)

      • Bayonet rush emergent marsh (S2)

   Shrublands, shrub thickets, and wooded swamps 

      • Mixed tall graminoid - scrub-shrub marsh (S4S5)

      • Highbush blueberry - winterberry shrub thicket (S4)

      • Buttonbush shrubland (S4)

      • Alder alluvial shrubland (S3)

      • Alder - dogwood - arrowwood alluvial thicket (S4)

      • Alder seepage thicket (S3)

      • Meadowsweet alluvial thicket (S3S4)

      • Mixed alluvial shrubland (S4)

      • Seasonally flooded red maple swamp (S4S5)

Landscape settings: along streams and small rivers in drainageways and in open headwater depressions

Soils: well decomposed muck and mineral soils, very poorly to poorly drained; moderately to strongly minerotrophic; pHs mostly in 5s and 6s; limnogenous

Spatial pattern: large patch (<1 - 200+ acres); extensive broad-linear shape with inlets and outlets; irregular or linear zonation (parallel to stream corridors and pond and lake margins)

Physiognomy: aquatic beds, herbaceous emergent and meadow marshes, medium and tall shrublands and shrub thickets, forested and woodland swamp

Distribution: widespread throughout New Hampshire

Characteristic species:
Common meadow marsh species (shallow variety):
Calamagrostis canadensis (bluejoint)
   Carex stricta (tussock sedge)
   Glyceria canadensis (rattlesnake mannagrass)
   Leersia spp. (cut grasses)
   Scirpus cyperinus (woolly bulrush)
   Carex utriculata (bottle-shaped sedge)

Common emergent marsh species:
Pontederia cordata (pickerel weed)
   Peltandra virginica (arrow arum)
   Sagittaria latifolia (common arrowhead)
   Sparganium americanum (lesser bur-reed)
   Eleocharis palustris (marsh spike-rush)
   Typha latifolia (common cattail)

Aquatic bed species:
Potamogeton spp. (pondweeds)
   Brasenia schreberi (water shield)
   Nuphar variegata (variegated yellow pondlily)
   Nymphaea odorata (white waterlily)
   Utricularia macrorhiza (common bladderwort)
   Lemna minor (lesser duckweed)
   Vallisneria americana (tapegrass)
   Myriophyllum spp. (water milfoils)
   Megalodonta beckii (water marigold)
   Persicaria hydropiperoides (mild water pepper)

Common species of shrub communities:
Ilex verticillata (winterberry)
   Vaccinium corymbosum (highbush blueberry)
   Alnus incana ssp. rugosa (speckled alder)
   Viburnum nudum var. cassinoides (witherod)
   Salix spp. (willows)
   Myrica gale (sweet gale)
   Spiraea alba (eastern meadowsweet)
   Cephalanthus occidentalis (buttonbush)

Seepage marsh species:
Alnus incana ssp. rugosa (speckled alder)
   Carex lacustris (lake sedge)
   Impatiens capensis (spotted touch-me-not)
   Onoclea sensibilis (sensitive fern)
   Eupatorium maculatum (spotted Joe-Pye weed)
   Symplocarpus foetidus (skunk cabbage)
   Aster puniceum (purple-stemmed aster)
   Toxicodendron vernix (poison sumac)
   Hydrocotyle americana (water pennywort)
   Carex stipata (awl sedge)
   Equisetum sylvaticum (wood horsetail)
   Osmunda regalis (royal fern)

Associated natural community systems: Emergent marsh - shrub swamp systems are found in association with some medium level fen systems and sometimes transition to oligotrophic peat swamp or minerotrophic swamp systems.

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