Natural Communities of NH -- Photo Guide

Sedge meadow marsh (S4)

(formerly northern medium sedge meadow marsh and fenny marsh)

Sedge meadow marshes
occur in seasonally flooded or seasonally saturated areas where water level fluctuations are relatively moderate compared to the other meadow marsh communities. Water levels remain close to the ground surface throughout the growing season. These sedge or sedge-grass meadows are transitional between marsh and fen, with emergent or meadow marsh plants mixing with fen sedges and peat mosses. Common settings for this community are relatively stagnant headwater basins, hydrologically isolated lobes of larger drainage marshes, and behind abandoned beaver impoundments. All of these are areas where lowered water levels allow for the accumulation of organic matter. This community also occurs on grounded peat mats in seasonally flooded portions of medium fens. 

The substrate is often saturated, with pHs between 4.4 and 5.7, and has relatively little microtopography. It usually consists of grounded, well-decomposed organic soils, or mineral soils with a high organic content.

Many examples are probably former swamps or medium level fen systems with grounded peat mats in beaver drainages, or late-successional emergent marsh beaver meadows that developed following dam-abandonment and subsequent paludification of the basin. These marshes likely succeed into a mixed tall graminoid - scrub shrub marsh or shrub swamp and depending on dominant hydrologic regime, to different types of forested swamps. With paludification, this community could become a fen, or, with renewed impoundment by beavers, retrogress to a wetter marsh or aquatic bed.

This community is distinguished from floating marshy peat mats by vegetation differences and a mostly grounded (rather than floating) substrate. It is distinguished from marshy moats by the moat's position along peatland margins and the relatively narrow width of most moats.

Characteristic Vegetation: There is often a significant cover (25% to over 50%) of Sphagnum moss, but the community is dominated by graminoids and forbs of at least weakly minerotrophic and more marshy tendencies (i.e., they are not restricted to fen habitats). Dominant plants usually include some combination of bottle-shaped sedge, silvery sedge, tussock sedge, prickly sedge, and peat mosses. Bluejoint may be common, but it is not as abundant as the sedges.

Characteristic species include silvery sedge (Carex canescens), tussock sedge (Carex stricta), bottle-shaped sedge (Carex utriculata), bluejoint (Calamagrostis canadensis), three-way sedge (Dulichium arundinaceum), northern blue flag (Iris versicolor), rushes (Juncus spp.), common water horehound (Lycopus uniflorus), swamp candles (Lysimachia terrestris), common arrowhead (Sagittaria latifolia), woolly bulrush (Scirpus cyperinus), lesser bur-reed (Sparganium americanum), Sphagnum moss, and marsh St. John's-wort (Triadenum virginicum).

Other species are prickly sedge (Carex echinata), lake sedge (Carex lacustris), wire sedge (Carex lasiocarpa), spike-rushes (Eleocharis spp.), St. John’s-worts (Hypericum spp.), cinnamon fern (Osmunda cinnamomea), flat-topped white aster (Doellingeria umbellata), and common cattail (Typha latifolia). Tree saplings, peatland heaths, and other shrubs typically occur with <5% cover and include red maple (Acer rubrum), speckled alder (Alnus incana ssp. rugosa), gray birch (Betula populifolia), buttonbush (Cephalanthus occidentalis), leatherleaf (Chamaedaphne calyculata), winterberry (Ilex verticillata), male berry (Lyonia ligustrina), sweet gale (Myrica gale), meadowsweet (Spiraea alba), steeple bush (Spiraea tomentosa), poison sumac (Toxicodendron vernix), and highbush blueberry (Vaccinium corymbosum).

Two variants are presently recognized:

Typic southern variant: 
   As described above. This variant is most common in central and southern New Hampshire and is distinguished from the next variant by the absence of species more frequent in northern NH [e.g., swollen-beaked sedge (Carex rostrata), northeastern spotted Joe-Pye weed (Eupatorium maculatum var. foliosum), and Fraser's marsh St. John's-wort (Triadenum fraseri)] and/or the presence of species more common in southern NH (e.g., poison sumac and highbush blueberry).

Northern medium sedge meadow variant: 
   This variant is dominated by medium sized sedges [0.3–0.6 m (1–2 ft.) high] and other herbs and occurs in old, abandoned, “filled-in” beaver marshes in montane settings in the northern part of the state. Characteristic species are prickly sedge, bottle-shaped sedge, and a diverse assemblage of marsh forbs. Other marsh plants may include bent-grasses (Agrostis spp.), bluejoint, tussock sedge, lake sedge, three-way sedge, northeastern spotted Joe-Pye weed, bedstraws (Galium spp.), rattlesnake mannagrass (Glyceria canadensis), St. John’s-worts, northern blue flag, Canada rush (Juncus canadensis), cutgrasses (Leersia spp.), common water horehound, woolly bulrush, purple-stemmed aster (Symphyotrichum puniceum), tall meadow-rue (Thalictrum pubescens), and Fraser's marsh St. John's-wort. The rare swollen-beaked sedge (Carex rostrata) can occur in this variant.

Good examples of this community occur at Pisgah State Park (Chesterfield), Deering Wildlife Sanctuary (Deering), Orenda-Stickey Wicket Wildlife Sanctuary (Marlow), Blackwater Flood Control area (Salisbury), Norton Pool Preserve (Pittsburg), and Elbow Pond (Woodstock).

Sedge meadow marshes often occur as part of larger emergent marsh - shrub swamp systems and medium level fen systems.

sedge meadow marsh in Stoddard/Nelson (photo by Dan Sperduto for the NH Natural Heritage Bureau)
Sedge meadow marsh in Stoddard/Nelson (photo by Dan Sperduto)

A sedge meadow marsh at Pisgah State Park (photo by Pete Bowman for the NH Natural Heritage Bureau)
A sedge meadow marsh at Pisgah State Park (photo by Pete Bowman)