Being on a shale barren feels a bit
like being in an old western. Hot. Dry. Gritty. Stunted trees and
copperheads, crumbling rock and open sky. All that's missing is the
withered old prospector. But you won't find gold in "them thar hills."
There's a different kind of treasure here.
The treasure of shale barrens is not
gold or silver. The hidden treasure of the shale barrens is the
collection of rare and endemic plants and animals, the unusual geology,
the extreme conditions that encourage patience and determination to
unlock the secrets of this rare and forbidding natural community.
Shale barrens, for the most part, occur
along a band of Devonian shale in the Ridge and Valley physiographic
province of the Appalachian Mountains. Locally, that means you can find
them in Allegany County; there are several good examples in
Green Ridge State Forest.
Shale barrens are the result of a
unique combination of geology, soil, topography and climate. At the
base of it all is bedrock, shale. Shale is a highly friable rock,
meaning it crumbles easily. Small fragments of rock, called "channers,"
cascade down the steep south- to west-facing slopes, creating a highly
unstable substrate. The soil is consequently shallow. It sheds water
easily so it tends toward a xeric, or dry, state. Rains hit the shale
and run off, causing erosion, resulting in crumbled rocks and loose
soil. Couple the lack of infiltration by water with the hot sun from a
southern exposure and you have desert-like conditions, especially in the
summer when temperatures on the outcrops easily exceed 100 degrees
This environment is not for every plant
or animal. These hostile conditions favor open canopies, often with
rock outcrops, and usually sparse woodlands of stunted drought-tolerant
trees with little herbaceous understory. Plant species composition and
density can vary with the acidity of the soil, with the more acid soils
supporting fewer scattered species and the neutral or basic soils
hosting a more developed herbaceous layer with higher diversity.
The most commonly found trees include scrubby forms of chestnut oak,
Virginia pine, eastern redcedar and pignut hickory. Other typical trees
include white ash, oaks (post, black and red), pines (table-mountain and
white), and shagbark hickory.
The few shrub species include shadbush,
black huckleberry, deerberry and bear oak. Many of the herbaceous
species that do occur on shale barrens are endemic or near-endemic,
meaning they are found on no other habitat type. Their names tell the
story: shale-barren pussytoes, shale-barren ragwort, shale-barren
Unusual habitats often support rare species and shale
barrens are a perfect example of this. Kate's-mountain clover,
yellow nailwort, and low false
bindweed are three rare species associated with shale barrens. Common
plants that occur on shale barrens can also be found on other natural
communities that also tend toward dry conditions; these species include:
wavy hairgrass, common dittany, rattlesnake-weed, poverty oat-grass,
little bluestem, birdfoot violet and reindeer lichens. Herbaceous
openings are sparsely vegetated and often scattered within a woodland
Even with these extreme conditions,
there are some animals that still call shale barrens their home.
Reptiles include five-lined skinks, eastern fence lizards, wood
turtles, copperheads and timber rattlesnakes. Birders will find pine
warblers, prairie warblers, Carolina wrens, common ravens and broadwing
hawks. Turkeys have been spotted soaring from the elevated heights of
the barrens to the floodplains of the Potomac below. The sunny
herbaceous openings provide patrolling areas for many skippers,
butterflies and moths. Several mammal species, both game and nongame,
can be found on shale barrens: white-tailed deer, eastern gray
squirrels, foxes, coyotes, striped skunks, bobcats, eastern red bats and
Even though many shale barrens are
remote, there are still threats to their existence. The greatest of
this is the encroachment of invasive species.
Certain non-native species, which have no natural control, are capable
of moving into an area and changing the conditions, adding organic
material to the soil and shade to the open canopy while crowding out the
native species. Non-native grasses, spotted knapweed, Japanese
honeysuckle, garlic-mustard and tree-of-heaven are all on the "Least
Wanted" list for shale barrens. Unfortunately, these species utilize
manmade disturbances, such as roads, logging, or agriculture as
corridors into the isolation of the barrens.
Maryland Department of Natural Resources
Wildlife and Heritage Service
Tawes State Office Building, E-1
Annapolis MD 21401
Toll-free in Maryland: 1-877-620-8DNR
580 Taylor Ave, Annapolis MD 21401