Natural Communities of NH -- Photo Guide

Sharp-flowered mannagrass shallow peat marsh  (S1)



Sharp-flowered mannagrass shallow peat marshes
are a wetland community characterized by semi-permanently flooded to intermittently-exposed, shallow peat swales dominated by the floating-stemmed sharp-flowered mannagrass, a species at the northern edge of its range. Other vegetation is sparse, but includes rattlesnake mannagrass, diverse-leaved water-starwort, various pondweeds, and yellow pond lily. Soils consiste of 10-35 cm of well-decomposed peat over a shallow sandy muck layer over sand to >1.2 m (histic and mineral histic epipedons). The community is very rare in New Hampshire.

Characteristic vegetation: Peat mosses (Sphagnum spp.; including S. cuspidatum) vary from being present in low abundance to being co-dominant with floating-stemmed sharp-flowered mannagrass (Glyceria acutiflora). Drawdown periods produce habitat for mud flat ruderals such as Smith's bulrush (Schoenoplectus smithii), Pennsylvania smartweed (Persicaria pensylvanica), nodding bur-marigold (Bidens cernua), common beggarticks (Bidens frondosa), swamp beggarticks (Bidens connata), fireweed (Erechtites hieraciifolia), and fall panic grass (Panicum dichotomiflorum), and for seedling establishment of Glyceria acutiflora. Other vegetation is sparse but includes rattlesnake mannagrass (Glyceria canadensis), diverse-leaved water starwort (Callitriche heterophylla), Oakes' pondweed (Potamogeton oakesianus), Tuckerman’s panic-grass (Panicum tuckermanii), and variegated yellow pondlily (Nuphar variegata). Lower central zones in this community may be dominated by seedlings of Glyceria acutiflora surrounded by an outer zone of mature fruiting plants, rooting at the nodes.


A good example of this community occurs on private land in south-central New Hampshire. There are no known examples on public land.

Sharp-flowered mannagrass shallow peat marsh occurs along with others as part of a sand plain basin marsh system.


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