Shale Barrens in Maryland

 

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 Fahrenheit.

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 evening primrose.

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 matrix.

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 many more.

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.

For more information, please contact:

Maryland Department of Natural Resources
Wildlife and Heritage Service
Tawes State Office Building, E-1
Annapolis MD 21401
410-260-8540
Toll-free in Maryland: 1-877-620-8DNR