Serpentine Barrens
This page is less about hiking and more about serpentine barrens — a unique type of threatened natural environment that I find fascinating.
Ninety percent of the serpentine barrens on the east coast are found in Maryland and Pennsylvania. There is an obscure natural area in Travilah in Montgomery County called the Serpentine Barrens Conservation Park. Someday it may be developed for hiking, but so far it has no public parking area or access, no trails, and no signage (other than no trespassing signs posted on the powerline swath that runs through its center). One way to access it: park at the end of Centurion Way, Rockville, MD, and follow the powerline swath to the right to get beyond the houses at the end of this street and into the woods. This is a pocket wilderness without trails. As you drive in to Centurion Way, notice how the landscaping of the adjacent houses reflects the peculiar stunted nature of the forest, making it look like a subdivision from someplace else, perhaps Florida. Soldiers Delight Natural Environment Area in Baltimore County is a 1,900-acre area that is the largest single eastern U.S. serpentine barrens site. It has more than 39 rare, threatened, or endangered plant species as well as rare insects, rocks and minerals. Soldiers Delight has a visitor center and seven miles of marked hiking trails.
There is a brief stretch of serpentine barrens along the Muddy Branch Trail, between Esworthy Road and Turkey Foot Road. It is on a hilltop where the trees are shorter and more widely spaced, there are some pines, and the vegetation is more sparse. Look around and you will see a lot of greenish serpentine rock on the ground in this section.
The landscape of serpentine barrens landscape tends to be prairie of mainly native grasses with scattered trees — usually pines, oaks, or junipers — and exposed rock. They tend to harbor rare species that are found elsewhere, in harsher, drier conditions. They often have thickets of native greenbrier and thorny vines.
The reason for the relative barrenness of the soil is that it has high levels of magnesium and nickel, and low levels of calcium, compared to other soils. This tends to favor plants that can handle nutrient stress. Serpentine soils have other distinctive qualities, but they may not account for the stress on plants. These include low levels of nitrogen, phosphorous, and potassium — the minerals needed by plants in greatest quantity (in addition to calcium). And the soils also have high levels of chromium and cobalt — two more metals known to be toxic to plants in high concentrations. Another theory is that serpentine soils are inhospitable to certain fungi that attack seedling plants, and their absence causes plants in serpentine soils to lose their resistance to these pathogens, so they become restricted to serpentine areas.
The Serpentine Barrens in Travilah has extensive thickets of greenbrier and leatherwood, an uncommon woody shrub. It's forest is more than 100 years old, with many species of oak, including white, northern red, black, post, blackjack, chestnut, swamp white, scarlet, southern red, shingle, willow. The post and blackjack oak and yellow or shortleaf pine are found nowhere else in Montgomery County. The trees are unusually small relative to their age because of the challenging growing conditions of serpentine soils. Therefore, forests appear to be early successional, but in reality are in a climax condition. Oaks as old as 175 years old will have a diameter of trees you would expect to be one or two decades old. Serpentine Barrens is an unusually large forest tract for this suburban setting that provides habitat for more than 60 species of bird, red fox, and eastern coyote. There are wetlands along Greenbriar Branch and other intermittent tributaries, vernal pools, and perched wetlands.
Serpentine barrens throughout eastern North America are under threat from ever-expanding agriculture, forestry, and mining activity, as well as fire suppression and urbanization. They tend to be strip mined or quarried for their minerals. Indeed, next to the Serpentine Barrens in Travilah is the 500-foot deep pit of the Rockville Crushed Stone Quarry that is mining the serpentine for high quality construction materials. The barrens are also at risk of losing their unique characteristics and plant community because they are not being allowed to burn periodically, which historically has helped maintain the distinctive the environment. Without periodic burns, Virginia pine, juniper, and buckthorn begin to replace the oaks, allowing a thicker soil to accumulate that supports a none-serpentine forest.
In Soldiers Delight, rare grassland plant species are threatened by invasion of Virginia pines. There is a five-year effort of underway to remove 1,000 acres of pines, and to allow prescribed burning to help the area return to natural serpentine habitat.
Fortunately, there are several serpentine preserves in the states of California, Oregon, and Washington, and in Cuba, Italy, New Caledonia, New Zealand, South Africa, and Sri Lanka, leading the way to raise awareness of the immediate need for the conservation of these unique biotas. There are several preserves in eastern North America, including the well-known Mt. Albert in Gaspesian Provincial Park, Quebec, Canada; Table Mountain in Gros Morne National Park, Newfoundland, Canada; State-Line Serpentine Barrens in Pennsylvania; Soldiers Delight; and Pine Hill Preserve, Deer Isle, Maine.
The name serpentine may come from the long, sometimes wiggly veins of minerals seen in some serpentine rocks. Or, because there are outcrops of mottled greenish bedrock in northern and northwestern Italy that are similar to those found in the barrens of Pennsylvania and Maryland. (The green color comes from chromium salts.) A snake tends to live among these rocks that has a similar mottled green coloration, allowing it to blend in and avoid hungry birds. Ancient peoples assumed that the snake and the rock were two different phases of the same mottled greenish substance, so they named the inanimate phase — the rock — serpentine.
Serpentine minerals are formed beneath the ocean floor in fracture zones — areas riddled with giant cracks from stresses created by the movement of oceanic crust plates. Seawater leaking into deep cracks reacts with olivine and pyroxene, minerals that are common constituents of a rock called peridotite, the dominant rock of the Earth's mantle — the layer beneath its crust. This reaction with water is a type of metamorphism called serpentinization, which causes the rocks to be enriched iron and magnesium, and the more toxic heavy metals (nickel, chromium, and cobalt). It also infuses the rock with oxygen and hydrogen, which makes it less dense than other oceanic rock. This sometimes allows it to float upward onto the surface of land as oceans close and continents collide. Serpentine rock can be carried further upward when land containing it is thrust up into mountains.
Pieces of this lighter oceanic crust that are found on land are usually found along coastlines, and are called ophiolites — a word coined from the Greek words for snake and rock. Ophiolites were first formed at the oceans' spreading centers, when new ocean crust was created, and they are eventually carried on ocean crust plates to the edge of continents, where they are sometimes pushed up onto land. The most extensive serpentine barrens in North America are in California and Oregon — on the younger coastline of western North America that has been the site of more recent (in geologically terms) continental collisions. In temperate eastern North America, serpentine barrens are found from Georgia to New York, but more than 90 percent of the acreage is in Pennsylvania and Maryland.
