Description:  This system occurs on summits and ridges from about 3,000 ft. to 4,900 ft. outside the Presidential Range and Franconia Ridge.  It is characterized by one or, less frequently, both of the two heath – krummholz communities and sometimes subalpine dwarf shrublands in more exposed areas.  A few peaks have extensive, sparsely-vegetated bedrock exposures classified as subalpine rocky balds.

The two heath – krummholz communities that are diagnostic of this system contain bilberry, cranberry, and blueberry heaths joined by various mixtures of Ledum groenlandicum (Labrador-tea) and Kalmia angustifolia (sheep laurel).  The lichens are common and often abundant.  Heath - krummholz communities occur as nearly pure dwarf shrublands (<10-15 cm tall) to mixtures of 20-60% krummholz.  Heath – krummholz usually has substantial rock, talus, gravel, or stone exposure (>25%).  Picea rubens (red spruce) is among the krummholz-forming trees below 3,500 ft., and Picea mariana (black spruce) appears above 3,500 ft.  Betula cordifolia (heartleaf birch) and Abies balsamea (balsam fir) are found throughout.  Sheep laurel - Labrador tea heath - krummholz occurs on peaks between 3,000 and 3,500 ft.; above this, sheep laurel, red spruce and other species drop out, marking the transition to Labrador tea heath - krummholz.  Typically either one or the other of these heath - krummholz communities is present, probably due to the restricted elevation range of the subalpine area on any given peak.

More exposed areas of this system on rocky or gravelly substrate correspond to subalpine dwarf shrubland (above 3,400 ft.) or subalpine rocky bald (mostly below 3,500 ft.) communities.  Floristically, the subalpine dwarf shrubland is intermediate between heath – krummholz and sedge – rush – heath communities; it lacks the abundance of Kalmia angustifolia (sheep laurel), Ledum groenlandicum (Labrador-tea), and krummholz patches found in heath – krummholz communities and has a lower abundance of Carex bigelowii (Bigelow’s sedge) and Juncus trifidus (highland rush) than found in the sedge – rush – heath community of higher elevations.  It occurs in exposed settings with shallow or ephemeral snow cover.  Vegetation is typically dwarfed (less than 20 cm in height) and dominated by crowberries, subalpine Vaccinium species, and Potentilla tridentata (three-toothed cinquefoil).  Higher elevation alpine tundra and alpine ravine/snowbank species are absent or intermittent in this system (see list under alpine tundra system).


Diagnostic natural communities:

      • Subalpine dwarf shrubland (S2)

      • Black spruce - balsam fir krummholz (S2S3)

      • Labrador tea heath - krummholz (S2)

      • Sheep laurel - Labrador tea heath - krummholz (S2)

      • Subalpine rocky bald (S2)


Peripheral or occasional natural communities:

      • Diapensia shrubland (S1)

      • Red spruce - heath - cinquefoil rocky ridge (S3S4)

      • Montane heath woodland (S2)

      • Montane level fen/bog


Landscape settings:  exposed summits and ridges

Soils: dry to moist, mostly very acidic, well drained, shallow organic and/or coarse mineral soils (sand, gravel) over bedrock or talus, with frequent rock outcrop exposures

Spatial pattern: small to large patch (<5 – 200+ acres), irregular zonation

Physiognomy: sparsely vegetated to dwarf shrubland structure with patches of krummholz (stunted trees < two meters tall)

Distribution: White Mountains and high elevations to the south from about 3,000 to 4,900 ft. elevation


Characteristic species:

Species characteristic of the heath – krummholz communities:
Krummholz trees (<2 m height)
   Betula cordifolia (heartleaf birch)
   Abies balsamea (balsam fir)

Shrubs 
   Ledum groenlandicum (Labrador-tea) 
   Vaccinium uliginosum (alpine bilberry)
   Vaccinium vitis-idaea (mountain cranberry)
   Vaccinium angustifolium (late low blueberry)
   Vaccinium myrtilloides (velvet-leaved blueberry) 
   Empetrum nigrum (black crowberry)
   Empetrum atropurpureum (purple crowberry)

Lichens
   Cladina rangiferina
   Cladina alpestris
   Cetraria islandica


Species restricted to sheep laurel type:
   Picea rubens (red spruce) 
   Kalmia angustifolia (sheep laurel) 
   Rhododendron canadense (rhodora) 
   Nemopanthus mucronatus (mountain holly)


Species restricted to Labrador tea type:
   Picea mariana (black spruce)

Species characteristic of subalpine dwarf shrubland:
Shrubs 
   Vaccinium uliginosum (alpine bilberry)
   Vaccinium vitis-idaea (mountain cranberry)
   Vaccinium angustifolium (late low blueberry)
   Potentilla tridentata (three-toothed cinquefoil)
   Empetrum nigrum (black crowberry)
   Empetrum atropurpureum (purple crowberry)
   Ledum groenlandicum (Labrador tea)
   Diapensia lapponica (diapensia) (>3,500 ft.)

Herbs
Occasional species:
   Carex bigelowii (Bigelow’s sedge)
   Juncus trifidus (highland rush) 
   Solidago cutleri (Cutler's goldenrod)

Lichens
   Cladina rangiferina
   Cetraria islandica

Species characteristic of subalpine rocky bald:
Shrubs 
   Rhododendron canadense (rhodora)
   Nemopanthus mucronatus (mountain holly)
   Kalmia angustifolia (sheep laurel)
   Vaccinium uliginosum (alpine bilberry)
   Vaccinium vitis-idaea (mountain cranberry)
   Vaccinium angustifolium (late low blueberry)
   Sibbaldiopsis tridentata (three-toothed cinquefoil) [formerly Potentilla tridentata]
   Empetrum nigrum (black crowberry)
   Empetrum atropurpureum (purple crowberry)
   Ledum groenlandicum (Labrador tea)

Herbs
   Minuartia groenlandica (mountain sandwort)
   Juncus trifidus (highland rush)

Lichens
   Cladina rangiferina
   Cetraria islandica


Associated natural community systems:  Most examples of this system occur at the tops of higher peaks outside of the Presidential Range and Franconia Ridge, and therefore do not transition to alpine tundra systems.  At lower elevations this system does often transition to montane rocky ridge system or high-elevation spruce - fir forest system.  In parts of the White Mountains, this system forms mosaics with alpine/subalpine bogs that have collectively been referred to as “heath balds.”  These “heath balds” occur mostly below 4,000 ft. elevation on flat to gently sloping ridgetops of the Mahoosuc, Carter-Moriah, and Baldface Ranges, with a few smaller examples found in several other scattered locations.

subalpine heath - krummholz/rocky bald system on Shelburne-Moriah Mtn. (photo by Ben Kimball)