Endangered Species Bulletin: Partners Restore Rare Serpentine Ecosystem

Serpentine "barrens" are rare natural communities composed of grasslands and oak savanna growing around outcrops of serpentine, a magnesium-rich mineral that contributes to dry, acidic, erodible, nutrient-poor soils. Despite their name, such habitats are not really barren. They contain a high percentage of rare species adapted to these harsh conditions.

Since colonial times, over 100,000 acres (40,470 hectares) of native serpentine habitat have been destroyed in the Mid-Atlantic region of the United States, leaving only small fragments of this unique ecosystem. But recently, the U.S. Fish and Wildlife Service's (FWS) Chesapeake Bay Field Office joined a partnership with the Maryland Department of Natural Resources' Heritage and Biodiversity Conservation Program and the Maryland/District of Columbia chapter of The Nature Conservancy to restore one of the largest and most biologically diverse serpentine habitats remaining: Soldier's Delight Natural Environment Area.

Prior to European settlement, Maryland contained over 50,000 acres (20,235 ha) of serpentine habitats, consisting of two primary plant communities: little-bluestem (Andropogon scoparius) dominated grasslands, and oak savanna characterized by stunted hardwoods, primarily blackjack oak (Quercus marilandica) and post oak (Q. stellata). Serpentine oak savanna is considered the State's rarest natural community.

For thousands of years, serpentine plant communities were maintained by periodic exposure to fires caused by lightning or set by Native Americans. Following the decimation of native peoples, pine and cedar trees invaded the serpentine savanna and grasslands. Many of the serpentine barren habitats have become dominated by conifers, while the native grassland and oak species have all but disappeared. Mining activities and recent residential development have destroyed most of the remaining serpentine habitats.

In Maryland, only four sites remain, totaling about 2,500 acres (1,010 ha). The largest, Soldier's Delight, is also the largest serpentine grassland in all of North America, with about 1,800 acres (730 ha) of serpentine soils. This site contains at least 28 state-listed threatened or endangered species, including 90 percent of all populations of the federally-listed sandplain gerardia (Agalinis acuta). The site also contains serpentine aster (Aster depauperatus), a candidate for Federal listing.

In 1996, the Maryland Department of Natural Resources began restoring hundreds of acres of serpentine barren habitat at Soldier's Delight. The FWS Partners for Fish and Wildlife program recognized the importance of this work to restoring viable populations of sandplain gerardia and maintaining biodiversity in Maryland. In 1997, Partners staff at the FWS Chesapeake Bay Field Office, in cooperation with the Maryland/D.C. chapter of The Nature Conservancy, joined the restoration team, contributing funds for contracting the manual site clearing and staff for surveying sandplain gerardia colonies.

Restoration actions include removal of large, invasive conifers and periodic, controlled burning to maintain grassland and savanna communities. First, pine trees were cut and manually removed from the site, uncovering small stands of scrub-type oaks, some of which are more than 100 years old. Due to the easily-compacted nature of serpentine soils, cutting and chipping activities were done manually, minimizing heavy equipment impacts. Project volunteers included local Soldier's Delight supporters, the Boy Scouts of America, and members of The Nature Conservancy. Last summer, the Partners program and Maryland Department of Natural Resources had trees removed from 50 acres (20 ha) of serpentine habitat at Soldier's Delight.

As with Midwestern prairie systems, species richness and productivity on serpentine barrens are maintained by frequent, low-intensity fires. Burns control colonization by conifers and greenbriar (Smilax sp.), which have overwhelmed the grasses and oaks over the past 50 years. Burning also encourages the growth of native warm-season grasses and rare serpentine community plants, including sandplain gerardia. Forty acres (16 ha) on which pines had been cut down were burned last fall. The burned area will be transformed into an oak savanna, complete with. native prairie grasses. Another 50 acres of serpentine habitat have been restored through cutting and will be burned sometime this fall.

These efforts are part of a long-term plan by the Maryland Department of Natural Resources, The Nature Conservancy, and the FWS to eliminate invasive plants and restore 1,000 acres (404 ha) of the serpentine ecosystem. Soldier's Delight provides exceptional opportunities for recovery of sandplain gerardia and research on eastern grassland communities. But perhaps more important is this area's value as a tool for teaching about rare habitats and associated biodiversity issues.

Laura Mitchell, formerly with the FWS Chesapeake Bay Field Office in Annapolis, Maryland, is now at Cornell University with the New York Cooperative Fish and Wildlife Research Unit.