Subalpine dwarf shrubland
Subalpine dwarf shrubland (S2)
(formerly dwarf shrub - bilberry - rush barren)
Subalpine dwarf shrublands occur on exposed, well-drained summits, upper slopes, and ridges from 3,400–4,800 ft., primarily on peaks outside the Presidential Range. It often occurs in association with heath - krummholz communities, but in locally more exposed settings where it lacks the abundance of sheep laurel (Kalmia angustifolia), Labrador tea (Ledum groenlandicum), and krummholz trees. This community is also floristically related to the sedge - rush - heath meadow of higher elevations but has a lower abundance of Bigelow’s sedge (Carex bigelowii) and highland rush (Juncus trifidus). It is essentially a subalpine analogue to sedge - rush - heath meadow and diapensia shrubland communities. Vegetation is typically dwarfed (up to 20 cm but most often less than 10 cm in height) and dominated by crowberries (Empetrum spp.), subalpine Vaccinium spp., and three-toothed cinquefoil (Sibbaldiopsis tridentata).
Soils consist of well drained gravel and stone in a sand matrix with or without a shallow organic-rich A horizon turf (usually <10 cm). Open exposures of rock, stone, or gravel typically consist of 25% or more of the ground surface. As with diapensia shrublands, winter snow cover is often thin and melts early, and freeze-thaw influence on soils is probably significant.
This community reaches its best development on the most exposed sites of subalpine peaks where it can occupy patch sizes of more than one acre. It also occurs as smaller patches in shallow, well drained soil areas around bedrock outcrops within heath - krummholz communities. Purple crowberry appears to be more abundant where highland rush and three-toothed cinquefoil are either absent or less abundant, perhaps indicating very well drained sites on stone or bedrock transitional to heath - krummholz communities.
Characteristic Vegetation: Dominant species include crowberries (Empetrum spp.), three-toothed cinquefoil (Sibbaldiopsis tridentata), and subalpine blueberries, cranberries, and bilberries such as alpine bilberry (Vaccinium uliginosum), mountain cranberry (Vaccinium vitis-idaea), and lowbush blueberry (Vaccinium angustifolium). There may be also a moderately low cover of highland rush (Juncus trifidus) and mountain sandwort (Minuartia groenlandica), with occasional patches of krummholz. Other species present in low abundances may include diapensia (Diapensia lapponica), tussock bulrush (Trichophorum cespitosum), common hairgrass (Deschampsia flexuosa), silverling (Paronychia argyrocoma), heartleaf birch (Betula cordifolia), Labrador tea (Ledum groenlandicum), and Cutler's goldenrod (Solidago cutleri).
Good examples of this community occur on Mt. Guyot, South and North Baldface Mtns., Bondcliff, Franconia Ridge, and Mt. Chocorua. These examples are all accessible by hiking trails. Two good examples not accessed by trail are on Whitewall Mtn. (above Zealand Notch) and the southeast ridge of Carter Dome.
Subalpine dwarf shrublands often occur as part of subalpine heath - krummholz/rocky bald systems.
Subalpine dwarf shrubland on South Baldface Mtn. (photo by Ben Kimball)
Subalpine dwarf shrubland on Mt. Cardigan (photo by Ben Kimball)
Subalpine dwarf shrubland on North Percy Peak (photo by Dan Sperduto)
1. black crowberry is a common plant of subalpine communities (photo by Dan Sperduto)
2. subalpine dwarf shrubland on South Baldface Mt. (photo by Dan Sperduto)