Natural Communities of NH -- Photo Guide


Alder - lake sedge intermediate fen  (S2S3)


(formerly speckled alder - lake sedge intermediate fen)

Alder - lake sedge intermediate fens
are dominated by medium shrubs, tall shrubs, and robust herbs. They occur in central and southern parts of the state, usually where there is enriched groundwater seepage influence. The prominence of shrubs, deeper organic soil, and greater abundance of peat moss separates this minerotrophic fen community from herbaceous seepage marshes; the abundance of herbs (25-90% cover) distinguishes it from other fen communities; and the absence or low cover of trees in the overstory (<25%) differentiates it structurally from seepage swamps.

In three examples, peat soils were one meter thick over sand or loam materials. Poorly decomposed surface peat transitioned to well decomposed peat within 20-30 cm of the surface. Hummock and hollow topography is well developed and pronounced. Measured pH ranges from 4.4 to 5.7. 

Characteristic Vegetation: The tall shrub layer varies from 5 to 40% cover, with Alnus incana (speckled alder) usually being the most abundant species. Others include Ilex verticillata (winterberry), Lyonia ligustrina (maleberry), Viburnum nudum (witherod), and Vaccinium corymbosum (highbush blueberry). Medium shrubs are usually abundant (5-50% cover). Frequent species include Chamaedaphne calyculata (leatherleaf), Myrica gale (sweet gale), Rhododendron canadense (rhodora), Spiraea alba (meadowsweet), Kalmia angustifolia (sheep laurel), K. polifolia (bog laurel), and Andromeda glaucophylla (bog rosemary).

Robust herbs that indicate a higher nutrient status and help distinguish it from winterberry - cinnamon fern wooded fen, sweet pepperbush wooded fen, and highbush blueberry - sweet gale - meadowsweet shrub thickets include lake sedge (Carex lacustris), royal fern (Osmunda regalis), and skunk cabbage (Symplocarpus foetidus). Less frequent or abundant herbs include Carex utriculata (bottle-shaped sedge), C. oligosperma (few seeded sedge), Calla palustris (wild calla), Lysimachia terrestris (swamp candles), Triadenum virginicum (marsh St. John’s-wort), Calamagrostis canadensis (bluejoint), and Smilacina trifolia (three-leaved false Solomon’s seal). Peat mosses (Sphagnum spp.) are abundant (20-80% cover) and include Sphagnum fallax, S. magellanicum, S. angustifolium, and S. flexuosum.

Trees may include eastern larch (Larix laricina), black spruce (Picea mariana), red maple (Acer rubrum), and gray birch (Betula populifolia). The rare swamp birch (Betula pumila) is sometimes found in this community.


A good example of this community occurs south of Ossipee Lake (Ossipee).

Alder - lake sedge intermediate fens sometimes occur as part of larger medium level fen systems.


an alder - lake sedge intermediate fen in Ossipee (photo by Dan Sperduto for the NH Natural Heritage Bureau)
an alder - lake sedge intermediate fen in Ossipee (photo by Dan Sperduto)

back to Natural Communities of NH Photo Guide