Serpentine barrens are geological areas containing soils derived from serpentinite rock. These soils are characterized by high concentrations of certain elements (such as chromium, cobalt, and nickel), low concentrations of others (such as nitrogen and phosphorus), and an imbalance of calcium (low concentration) to magnesium (high concentration). The chemical makeup of the soils usually results in low water availability. Altogether, the conditions limit which species of plants can grow there.
Serpentine soils can be found worldwide, but serpentine barrens are found only in certain parts of the Appalachian Mountains and the Pacific Coast Ranges. In the east, the largest of these ecosystems are found in Pennsylvania, and in Maryland, at Soldier’s Delight Natural Environment Area (1,900 acres in Baltimore County) and the Serpentine Barrens Conservation Park (256 acres in Montgomery County).
The latter is the place mentioned in my last post. I can’t even find a formal map of the area, but it’s apparently divided into three units. The larger serpentine barrens area seems to occur north and south of Travilah Road, from about Piney Meetinghouse Road in the east to about Sandy Branch in the west. The two North Units are on either side of the Pepco right-of-way that extends west from Piney Meetinghouse Road, south of the stone quarry.
I couldn’t find an exact count of RTE (rare, threatened, endangered) plant species in this park, nor could I find a list, but it’s well known as an RTE hot spot. I didn’t find any RTEs last week, but I did find five species that I haven’t seen elsewhere in the Piedmont.
One of the neat things about this particular serpentine barrens is that despite what you’d expect from the name, most of it is forested. Years ago when I lived in the area I would drive by and wonder why all the trees seemed so stunted. They’re short enough that you might think the area an early-stage successional woodland, but actually it’s climax-stage. On careful observation you can see that the trees are mostly much stouter than trees of the same height in neighboring areas.
More on the “new to me” species in coming days.
Further Reading (in addition to the links above):
Serpentine Barrens (DC Great Outdoors)
North America Serpentine Flora (Smithsonian Institution National Museum of Natural History)
Serpentine Soil (Wikipedia)
Natural Communities – Serpentine Grasslands (Maryland DNR)
a detailed geological map (note: this map can be fussy and not load properly, but if it does load will show the extent of the ultramafic rock formation underlying the Serpentine Barrens Conservation Park, the major rock being serpentinite)