Hemlock - beech - oak - pine forest  (S5)

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Hemlock - beech - oak - pine forests are one of the most common upland forest communities in southern and central parts of the state. They contain a wide mix of tree species, often indicative of a forest recovering from agriculture or past management. Hemlock and beech are the primary late- successional dominants. Early to mid-successional species include red oak, white pine, red maple, and black birch, or paper birch. Understory species vary widely, but often include witch hazel and wintergreen. Species more typical of Northern Hardwood Forests, such as northern wood sorrel and blue-bead lily, are absent or sparse. 

Bedrock beneath this community tends to be igneous or siliceous metamorphic rock that produces acidic soils with low nutrient availability. Soils are moderately to extremely well drained, dry-mesic to mesic loamy sands and sandy loams of varying degrees of stoniness and seasonal water availability. As with most upland forests of the region, single-tree windthrow is the primary natural disturbance, with occasional larger blowdown from hurricanes. Both soil and disturbance related variation is apparent. These forests are latitudinally, elevationally, and floristically transitional between northern hardwood forests and Appalachian oak - hickory forests. 

Characteristic vegetation: Hemlock (Tsuga canadensis), American beech (Fagus grandifolia), red oak (Quercus rubra), and white pine (Pinus strobus) are the primary mid to late successional tree species, and each is present in fully intergrading degrees of prominence. Since most examples in the state are early to mid successional, hemlock and beech may be present primarily in the understory or otherwise increase in prominence over time. At the extreme ends of the canopy-gradient, either hemlock or beech dominates to the exclusion of nearly all other tree species (these types are described as separate communities; see hemlock forest, hemlock - white pine forest, and beech forest). Other abundant or frequent early to mid- successional tree species include paper birch (Betula papyrifera), red maple (Acer rubrum), and striped maple (Acer pensylvanicum). Other occasional species that may be present in low abundance includeblack cherry (Prunus serotina), black birch (Betula lenta), sugar maple (Acer saccharum), white ash (Fraxinus americana), yellow birch (Betula alleghaniensis), and gray birch (Betula populifolia). Red spruce and balsam fir are uncommon or absent.

Canopy dominance combinations vary and may yield primarily hardwoods, a mix of hardwood and conifer, or mostly conifer-dominated stands. Hemlock prefers more mesic to wet-mesic, coarse or infertile soils, or sites with distant fire histories. Beech tends to occur on drier to more mesic coarse soils (e.g., washed tills. White pine grows well on early to mid-successional sites of all types, particularly those with an agricultural history, and does well longer term on either drier, coarser soils or those with fire histories. Black birch reaches its best development on mesic sites, but it may be present on somewhat drier sites as well.

The understory association of woody and herbaceous plants is reasonably distinct from northern hardwood and spruce - fir forests. Good differential species that are found primarily in this community include witch hazel (Hamamelis virginiana) and wintergreen (Gaultheria procumbens). Species that are less frequent or abundant than in northern hardwoods include northern wood sorrel (Oxalis montana), shining clubmoss (Huperzia lucidula), Canadian honeysuckle (Lonicera canadensis), mountain wood fern (Dryopteris campyloptera), blue-bead lily (Clintonia borealis), and twisted stalks (Streptopus spp.). Other characteristic species, many of which also occur in northern hardwood forests, include wild sarsaparilla (Aralia nudicaulis), sessile-leaved bellwort (Uvularia sessilifolia), intermediate wood fern (Dryopteris intermedia), beechdrops (Epifagus virginiana), partridgeberry (Mitchella repens), starflower (Trientalis borealis), Indian pipes (Monotropa uniflora), and Canada mayflower (Maianthemum canadense). The globally rare small whorled pogonia (Isotria medeoloides) is also preferential to this forest type.

This community grades into oak - pine forests on drier soils, to northern hardwood forests such as sugar maple - beech - yellow birch forest in the mountains and at higher elevations, and to mesic Appalachian oak - hickory forest in southern New Hampshire. The low abundance and frequency of sugar maple and yellow birch help distinguish it from hemlock - oak - northern hardwood forests.

Variants: Two variants are currently described.

1. Typic variant: 
   As described above. This variant is found on dry-mesic to mesic terrace flats and ablation till soils, generally with no seasonally high water table. 

2. Compact till/low river terrace variant: 
   This variant has a seasonally high water table and is found on low river and kame terraces or on compact basal till soils with a densipan. Soils include Paxton, Woodbridge, Skerry, Scituate series, including drumlin landscapes, or mesic river and kame terrace soils also with seasonally high water tables (e.g., Ninigret or Sudbury soil series). In addition to many of the understory plants described for the typic variant, ferns can be prominent on these sites including New York fern (Thelypteris noveboracensis), cinnamon fern (Osmunda cinnamomea), interrupted fern (Osmunda claytoniana), northern lady fern (Athyrium filix-femina var. angustum), and hay-scented fern (Dennstaedtia punctilobula; especially in gaps). Clubmosses (Lycopodium spp.) are frequent. White ash (Fraxinus americana) is often present in low abundance on compact till sites, and rattlesnake plantains (Goodyera spp.) are occasional. American hazelnut (Corylus americana) or beaked hazelnut (Corylus cornuta) are frequent on river terraces (beaked hazelnut extends further north).


Good examples of hemlock - beech - oak - pine forest (HBOP) can be seen at Hemenway State Forest (Tamworth), College Woods (Durham), Sheldrick Forest Preserve (Wilton), Five Finger Point (Sandwich), Hollis Town Forest (Hollis), and Chase Hill (Albany).

This community often occurs as part of a larger hemlock - hardwood - pine forest system.

Hemlock - beech - oak - pine forest (HBOP) community in Hollis, NH (photo by Ben Kimball)


Hemlock, beech, oak, and pine in a forest in Stratham (photo by Ben Kimball)


Old hemlock - beech - oak - pine forest at UNH's College Woods (photo by Ben Kimball)


Hemlock - beech - oak - pine forest at St. Gaudens National Historic Site
in the CT River Valley (photo by Ben Kimball)

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