Natural Community Systems -- Photo Guide

Northern hardwood - conifer forest system

Northern hardwood - conifer forest system near North Baldface Mtn. (photo by Ben Kimball for the NH Natural Heritage Bureau)
Northern hardwood - conifer forest system near North Baldface Mtn. (photo by Ben Kimball)

Northern hardwood - conifer forest system near the Kancamagus Highway (photo by Ben Kimball for the NH Natural Heritage Bureau)
Northern hardwood - conifer forest system near the Kancamagus Highway (photo by Ben Kimball)
 

Description New Hampshire’s northern hardwood forests are characterized by Fagus grandifolia (American beech), Acer saccharum (sugar maple), and Betula alleghaniensis (yellow birch).  These forests are positioned latitudinally and elevationally between the high-elevation spruce - fir forest and hemlock - hardwood - pine forest systems.  Northern hardwood forests are generally found between 1,4002,500 ft. in elevation in northern NH and along the western highlands (Sunapee Uplands subsection), although the tolerance range of individual species varies.  Some occurrences can be found down to about 1,000 ft. elevation.

The upslope ecotone to spruce - fir forest is marked by the appearance of Picea rubens (red spruce), Abies balsamea (balsam fir), the increased importance of yellow birch, and the disappearance of sugar maple and beech; the downslope ecotone to the hemlock - hardwood - pine forest system is marked by the appearance of more Tsuga canadensis (hemlock) along with Quercus rubra (red oak), Pinus strobus (white pine), and occasionally Ostrya virginiana (ironwood) and decreased dominance of yellow birch and sugar maple.

The matrix forest community type of this system, sugar maple - beech - yellow birch forest, mixes with patches of several other communities.  Hemlock - oak - northern hardwood forests occur at lower elevations (8002,000 ft.) and are differentiated from the matrix community by a substantial presence of hemlock.  It occurs in valley bottoms and lower mountain slopes of the White Mountains, and middle to higher elevations of hills and low mountains of the Sunapee Uplands subsection of western New Hampshire.  Hemlock - spruce - northern hardwood forests are also found at elevations below 2,000 ft.  This is a conifer to mixed community type with considerable hemlock and spruce mixing with variable amounts of birches, other northern hardwoods, balsam fir, and sometimes white pine.  It occurs primarily on river terraces, stream ravines, and compact till settings in the mountains where it transitions to more pure northern hardwoods on better soils (e.g., fine tills).  Semi-rich mesic sugar maple forests are a common but relatively small part of the mosaic formed by this system where there is slightly enriched till or fine river terrace sediments.  Both beech forest and hemlock forest types are occasional in this and the hemlock - hardwood - pine forest systems, but they generally only form relatively small patches.  Northern hardwood - spruce - fir forests mark the transition to high-elevation spruce - fir forest, but in most cases are considered part of the northern hardwood - conifer forest system because the hardwood trees that disappear in high-elevation spruce - fir (due to climate and/or soil conditions) are still present.  Some spruce - fir or mixed forests that have been cut or heavily disturbed may currently support a hardwood or mixed forest canopy, and may or may not succeed to greater spruce - fir prominence.


Diagnostic natural communities:

      • Sugar maple - beech - yellow birch forest (S5) – matrix forest type

      • Hemlock - spruce - northern hardwood forest (S3S4)

      • Hemlock - oak - northern hardwood forest (S4)

      • Semi-rich mesic sugar maple forest (S3S4)

      • Northern hardwood - spruce - fir forest (S4)


Peripheral or occasional natural communities:

      • Beech forest (S4)

      • Hemlock forest (S4)


Landscape settings: mountains, high hills, and mountain valleys

Soils: loose and firm glacial till, glacio-fluvial soils (e.g., river and kame terraces, outwash), stabilized talus

Spatial pattern: matrix (<10–1,000+ acres); irregular and linear zonation of component communities

Physiognomy: forest

Distribution: 1,4002,500 ft. elevation in northern NH and along the western highlands; occasionally found down to about 1,000 ft. elevation in cool, mesic settings


Characteristic species:

Characteristic species of the northern hardwood – conifer forest system:
   
Trees -- hardwoods
      Acer saccharum (sugar maple)
      Fagus grandifolia (American beech)
      Betula alleghaniensis (yellow birch)
      Acer rubrum (red maple)
      Betula papyrifera (paper birch) 
      Acer pensylvanicum (striped maple)
      Prunus pensylvanica (pin cherry)
      Fraxinus americana (white ash)

   Trees -- conifers
      Tsuga canadensis (hemlock)
      Abies balsamea (balsam fir)
      Picea rubens (red spruce)
      Pinus strobus (white pine) – infreq. at low elev.

Understory species absent or less frequent in communities of hemlock – hardwood – pine forest system:
   
Herbs and fern allies
      Clintonia borealis (bluebead lily)
      Huperzia lucidula (shining clubmoss)
      Dryopteris campyloptera (mountain wood fern)
      Oxalis montana (northern wood sorrel)
      Aster acuminatus (whorled aster)
      Streptopus lanceolatus (rose twisted stalk)

   
Shrubs & dwarf shrubs
      Acer spicatum (mountain maple)
      Viburnum lantanoides (hobblebush)
      Cornus canadensis (bunchberry)
      Coptis trifolia (goldthread)
      Lonicera canadensis (Canadian honeysuckle)
      Polystichum braunii (Braun’s holly fern)

Species common to communities of both systems:
      
Dryopteris intermedia (intermediate wood fern)
      Aralia nudicaulis (wild sarsaparilla)
      Trientalis borealis (starflower)
      Uvularia sessilifolia (sessile-leaved bellwort)
      Epifagus virginiana (beechdrops)
      Maianthemum canadense (Canada mayflower)
      Mitchella repens (partridgeberry)
      Monotropa uniflora (Indian pipes)

Species infrequent in northern hardwood – conifer system (characteristic of hemlock – hardwood – pine forests):
      
Betula lenta (black birch)
      Betula populifolia (gray birch)
      Prunus serotina (black cherry)
      Quercus rubra (red oak)
      Hamamelis virginiana (witch hazel)
      Gaultheria procumbens (wintergreen)
      Viburnum acerifolium (maple-leaved viburnum)


Associated natural community systems:  Upslope, this system transitions to high-elevation spruce – fir forest system.  Downslope they transition to either 1) hemlock – hardwood – pine forest systems, especially in low elevation valleys of White Mountains and further south; or 2) lowland spruce – fir forest/swamp systems in the North Country and some valley bottoms in the White Mountains.



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