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Hilltop Scrub
Description
On rocky hilltops where there is a thin persistent soil cover, an association of shrubs and stunted trees forms. Trees are few and scattered, and the shrubs often form dense thickets.
This association occurs mixed with balds and hilltop woods, often in a complex mosaic.
Selected Plants
The top of Mount Misery
Trees
- Pinus rigida (Pitch pine)
- Quercus montana (Chestnut oak)
- Prunus pensylvanica (Fire cherry)
Shrubs
- Quercus ilicifolia (Bear oak)
- Vaccinium angustifolium (Lowbush blueberry)
- Gaylussacia baccata (Huckleberry)
- Comptonia peregrina (Sweet-fern)
- Aronia arbutifolia (Chokeberry)
Herbs
- Danthonia spicata (Poverty grass)
- Schizachyrium scoparium (Little bluestem)
- Carex pensylvanica (Sedge)
- Deschampsia flexuosa (Hairgrass)
Occurrence
The top of Black Rock
Hilltop scrub is found at the top of Black Rock and along the ridges of Rattlesnake Hill and Sackett. Sites are usually small, often ringing hilltop meadows.
A good example of a scrub association formed by a recent fire can be seen on the ridge of Mount Rascal.
Ecology
Soil depth determines which type of association occurs on a hilltop site. The thinnest soils have grassy meadows. Slightly thicker and more permanent soils support shrub associations. Deeper soils alllow trees to grow and sparse woodlands to develop.
Fire is also an important factor. The hilltops become extremely dry by midsummer and are very vulnerable to fire. Organic matter in dry soils can burn readily, and fire can kill off the aboveground portions of trees and shrubs.
Hilltops are also exposed to cold, dry winter winds that can kill exposed buds and branches, often sculpting trees into bonsai-like shapes.
History
Hilltop shrub was probably more widespread in the past, when hilltop trees were cut for firewood or charcoal and fires were not vigorously suppressed.
Also Called
- Raup (1938): Scrub oak—pitch pine association
- Eyre (1980): 43. Bear Oak
- Breden (1989): Ridgetop pitch pine—scrub oak forest (part)
- Reschke (1990): Pitch pine—oak—heath rocky summit
- Collins & Anderson (1994): Hilltop
- NVCS: Quercus ilicifolia shrubland alliance
For general references see the reference page.
Photos: Paul Harwood, Kerry Barringer