Natural Communities of NH -- Photo Guide

Semi-rich oak - sugar maple forest  (S2S3)


(formerly semi-rich Appalachian oak - sugar maple forest)

Semi-rich oak - sugar maple forest occurs at low elevations in central and southern New Hampshire, mostly below 1,500 feet. It is dominated by oaks, sugar maple, and white ash, with a moderate to well developed woody understory and a scattered to moderately abundant herb layer. Examples of these forests that occur on steep or flat river terraces can have diverse tree and shrub layers. 

This community is similar to semi-rich mesic sugar maple forest, but occurs on sites that are somewhat drier and contains significant amounts of Appalachian species such as shagbark hickory (Carya ovata), ironwood (Ostrya virginiana), white ash (Fraxinus americana), black oak (Quercus velutina), and other southern or drier site species, especially in southern examples below 1,000 feet elevation. It is distinguished from more nutrient-poor forest types by having species indicative of weakly enriched conditions, and from rich mesic forests by the absence of strong enrichment indicators (see below). It also lacks many of the rare and uncommon species diagnostic of rich rocky woods communities.

Soils are well to moderately well drained fine sandy loams, loams, or silt loams with a very shallow hemic O horizon (1-2 cm+), shallow very dark gray to brown A horizons (2-10 cm), and brown to yellowish brown upper B horizons. Moisture availability ranges from dry-mesic to mesic and may be at least seasonally drier than most rich mesic forests. Bedrock types include formations that are mafic or have intermediate base-cation content such as diorites and gabbros, and the Elliot, Berwick and Kittery formations. Some sites have silty soils associated with marine deposits. Settings range from flat to moderately sloped terrain or colluvial positions at slope bases.

Characteristic Vegetation: This community is characterized by a moderately diverse tree canopy dominated by a combination of sugar maple (Acer saccharum), red oak (Quercus rubra), and white ash (Fraxinus americana). White pine (Pinus strobus) is frequent. Basswood (Tilia americana), black birch (Betula lenta), and black cherry (Prunus serotina) are occasionally present in some abundance, but not as constant as the other dominants. Hemlock (Tsuga canadensis) is occasional but never dominant (<15%), and beech (Fagus grandifolia) is infrequent and not abundant. Ironwood (Ostrya virginiana) is often abundant or dominant in the understory, and musclewood (Carpinus caroliniana) is occasionally abundant. Among these trees sugar maple, ash, basswood, ironwood, and musclewood are usually indicative of at least somewhat enriched conditions.

Tall shrubs include an abundance of maple-leaved viburnum (Viburnum acerifolium) and lesser amounts and constancy of witch hazel (Hamamelis virginiana), northern arrowwood (Viburnum dentatum var. lucidum), and beaked hazelnut (Corylus cornuta). Barberries (Berberis spp.) are common in disturbed examples.

Any combination of three or more of the following semi-rich differential species will distinguish the type from more acidic forests: Christmas fern (Polystichum acrostichoides), blunt-lobed hepatica (Anemone americana), hairy Solomon's seal (Polygonatum pubescens), wide-leaved sedges (Carex blanda, C. laxiflora, and C. laxiculmis), red baneberry (Actaea rubra), cluster-leaved tick trefoil (Desmodium glutinosum), broad beech fern (Phegopteris hexagonoptera), round-leaved violet (Viola rotundifolia), foamflower (Tiarella cordifolia), and poison ivy (Toxicodendron radicans). Most sites have only a few of these differential species. The following species may be found in more mesic microhabitats: Jack-in-the-pulpit (Arisaema triphyllum), sensitive fern (Onoclea sensibilis), interrupted fern (Osmunda claytoniana), small enchanter's nightshade (Circaea alpina), violets (Viola spp.), and white avens (Geum canadense).


Other characteristic species that may present (and are not restricted to enriched conditions) include partridgeberry (Mitchella repens; often abundant), spinulose wood fern (Dryopteris carthusiana), intermediate wood fern (Dryopteris intermedia), starflower (Trientalis borealis), northern lady fern (Athyrium filix-femina var. angustum), sessile-leaved bellwort (Uvularia sessilifolia), blue-stemmed goldenrod (Solidago caesia), Canada mayflower (Maianthemum canadense), wild sarsaparilla (Aralia nudicaulis), and Indian pipes (Monotropa uniflora).

Various other species of northern hardwood and transition hardwood forests tend to be absent. The broader range of enriched site species noted for rich mesic forests are also lacking (though all of the above mentioned species may also occur in that community). Some of these indicators of strong enrichment that are notably absent include blue cohosh (Caulophyllum thalictroides), wild ginger (Asarum canadense), maidenhair fern (Adiantum pedatum), and Goldie's fern (Dryopteris goldiana)

Variants: Two variants are described.

1. Typic variant

   (as described above).

2. Appalachian variant

   This variant can contain any of the species found in the typic variant, but also includes a significant component of Appalachian species in the tree canopy, particularly shagbark hickory (Carya ovata). Other diagnostic species include black oak (Quercus velutina), white oak (Q. alba), and flowering dogwood (Cornus florida).


Good examples of this community occur in the Crommet Creek vicinity (Durham), at the Merrimack River Conservation Center (Concord), and at Pawtuckaway State Park (Nottingham).

Semi-rich oak - sugar maple forestoften occur as part of larger rich Appalachian oak rocky woods systems and Appalachian oak - pine forest systems, and sometimes as part of rich mesic forest systems.


 Semi-rich oak - sugar maple forest on Cave Mtn. (photo by Dan Sperduto for the NH Natural Heritage Bureau)
Semi-rich oak - sugar maple forest on Cave Mtn.
(photo by Dan Sperduto)

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