Natural Communities of NH -- Photo Guide

Black spruce swamp  (S3)

(formerly black spruce - larch swamp, which was split into this community and larch - mixed conifer swamp

Black spruce swamp
 occurs in northern New Hampshire. Black spruce dominates this classic “bog forest” community (the endpoint of the peatland successional sequence), which often surrounds open bogs or fens or simply dominates entire closed-canopy, forested basins. This is a forest or woodland swamp found either on nutrient-poor, moderately deep to deep peat soils in stagnant basins or in stagnant areas within other wetland complexes. Several species of peat mosses (Sphagnum spp.) cover the ground. This community differs from red spruce swamps and larch - mixed conifer swamps by four factors: a shift to black spruce in the tree canopy, usually a greater abundance or dominance of dwarf heath shrubs, lower abundance and frequency of cinnamon fern (Osmunda cinnamomea), and generally deeper, wetter, and more nutrient-poor peat soils.

Black spruce exceeds 250 years of age in some New Hampshire swamps. While relatively intolerant of shade, this species is tolerant of saturated conditions. It can adjust to changing water conditions by producing adventitious roots from the stem, layering from branches, and (to some extent) by root sprouting. Black spruce usually dominates on oligotrophic peatlands of low pH (3.0-4.0), a pattern which relates well to the general ecological principal that coniferous evergreen species have a competitive advantage at low-nutrient sites because of the higher nutrient-use efficiency afforded by evergreen foliage.

Soils consist of organic muck and peat material greater than 40 centimeters in depth. They are typically moderate to deep (>0.5 m) and nutrient-poor (oligotrophic). Some of these swamps have shallower peat soils and mix with lowland spruce - fir forests dominated by red spruce and balsam fir. Most sites are saturated, with the water table at or near the surface most of the year.

Moderately large examples are found only in the six northernmost subsections of the state. Small disjunct examples are associated with open peatlands or stagnant basins in the Coastal Plain and Coastal Lowland subsections. Elevations mostly range from 1,000-3,500 ft., with small examples in the southern part of the state occurring as low as ca. 200 ft.

Characteristic vegetation:
Black spruce (Picea mariana) forms a discontinuous canopy cover of 25% to >80%, usually with a moderate to dense dwarf heath shrub layer, a variable tall shrub layer, an abundance of three-seeded sedge (Carex trisperma var. trisperma), and a low to modest cover of other herbs. Tall shrubs include mountain holly (Nemopanthus mucronatus), witherod (Viburnum nudum var. cassinoides), male berry (Lyonia ligustrina), and black chokeberry (Photinia melanocarpa). Dwarf heath shrubs include Labrador tea (Ledum groenlandicum), sheep laurel (Kalmia angustifolia), rhodora (Rhododendron canadense), velvet-leaf blueberry (Vaccinium myrtilloides), leatherleaf (Chamaedaphne calyculata), bog laurel (Kalmia polifolia), small cranberry (Vaccinium oxycoccos), and creeping snowberry (Gaultheria hispidula).

Herbaceous plants include peatland-restricted species such as three-leaved false Solomon's seal (Maianthemum trifolium) and pitcherplant (Sarracenia purpurea), as well as other northern plants including goldthread (Coptis trifolia) and bunchberry (Cornus canadensis). Cinnamon fern (Osmunda cinnamomea) is occasional. A diversity of peat moss species (Sphagnum spp.) cover the entire ground surface. 

Two variants are described.

1. Typic woodland variant:

   As described above. This variant includes most examples north of and including the White Mountain region. Note: A more closed-canopy expression of this variant, with a less well developed heath layer, a sparse to moderate tall shrub layer, and a well developed moss layer may deserve recognition as its own variant.

2. Southern highbush blueberry - huckleberry variant
This variant includes examples in southern and central New Hampshire containing species that reach their northern limit in central New England, including black huckleberry (Gaylussacia baccata) and highbush blueberry (Vaccinium corymbosum).

Good examples of this community occur at Bradford Bog (Bradford), Cape Horn State Forest (Northumberland), Norton Pool (Pittsburg), South Bay Bog (Pittsburg), Spruce Swamp (Fremont), and Whitewall Mountain (Bethlehem).

Black spruce swamps often occur as part of black spruce peat swamp systems, and sometimes as part of near-boreal minerotrophic peat swamp systems.

Black spruce swamp in Lancaster, NH (photo by Ben Kimball)

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