Sandplain Grasslands
by Dr. Sarah D. Oktay
Managing Director UMass Boston Nantucket Field Station
I am hoping many of you have already heard about one of the most prized habitats on Nantucket, the Sandplain Grassland, but this time of year is one of the best times to go see and enjoy them, so I thought a refresher might be helpful. According to the Natural Heritage & Endangered Species Program (Mass Natural Heritage), which is part of the Massachusetts Division of Fisheries & Wildlife, sandplain grasslands are defined as grassland communities on flat outwash plains with dry, low nutrient soils. Most occurrences are near the ocean and within the influence of high winds and the salt spray of storms. The community grades into sandplain heathlands, shrublands, dunes, or forest in various areas around the island. Sandplain grasslands have a state ranking (SRANK) of S1, which means that this habitat is critically imperiled in the state of Massachusetts. Excellent examples of sandplain grasslands on Nantucket can be seen at Ram’s Pasture at Sanford Farm, Head of the Plains, and the Linda Loring Nature Center off Eel Point, among others. They are generally found on the southern portion of the island, geologically known as the outwash plain, where fine sand and debris were deposited by glacial meltwaters.
Grasslands are dominated by graminoids (grasses and grasslike plants, including sedges and rushes), usually little blue stem grass (Schizachyrium scoparium), Pennsylvania sedge (Carex pensylvanica), and poverty oatgrass (Danthonia spicata), with bearberry (Arctostaphylos uva-ursi), scrub oak (Quercus ilicifolia), stiff aster (Ionactis linariifolius, formerly Aster linariifolius), bayberry (Myrica pennsylvanica), lowbush blueberry (Vaccinium angustifolium), and black huckleberry (Gaylussacia baccata) trying to muscle in here and there. There can be a fair amount of species overlap with sandplain heathlands, but sandplain grasslands are much richer in vascular species. A vascular plant is any plant containing food-conducting tissues (the phloem) and water-conducting tissues (the xylem). These include ferns and seed-bearing plants but not mosses or algae. Sandplain grasslands are transient communities that quickly colonize cleared areas, and then quickly succumb to succession by shrubs.
Rare plants found in sandplain grasslands within the past 25 years on Nantucket include: Nantucket shadbush (Amelanchier nantucketensis), purple needlegrass (Aristida purpurascens), purple milkweed (Asclepias purpurascens), eastern silvery aster (Symphyotrichum concolor endangered in MA), commons’ panic grass (Dichanthelium ovale ssp. Pseudopubescens – great name), birdfoot violet (Viola pedata), Sandplain Flax (Linum intercursum; of special concern in MA), purple cudweed (Gamochaeta purpurea), New England blazing star (Liatris scariosa var. novae-angliae), sandplain blue eyed grass (Sisyrinchium arenicola), papillose nut sedge (Scleria pauciflora var. caroliniana), and bushy rockrose (Helianthemum dumosum; threatened and globally rare). Use this link: http://www.mass.gov/dfwele/dfw/nhesp/townn.htm, to find out what type of rare and endangered things live in your city in Massachusetts. Threatened species recognized by Mass Natural Heritage as likely to out-compete the species above include exotics such as scotch broom (Cytisus scoparius), Japanese knotweed (Polygonum cuspidatum), cypress spurge (Euphorbia cyparissias), and cool season grasses such as sheep fescue (Festuca ovina), sweet vernal grass (Anthoxanthum odorata), velvet-grass (Holcus lanatus), and bluegrass (Poa pratensis).
The coastal areas of Cape Cod and Long Island, including Block Island, the Elizabeth Islands, Martha’s Vineyard, and Nantucket have historically hosted large areas of the sandplain grassland community. However, the coastal sandplain habitat has been all but eliminated on Cape Cod and Long Island due to development, agriculture, the reduction of grazing, and fire. It is estimated that over 90% of the remaining sandplain habitat in the world is located on the islands of Nantucket, Martha’s Vineyard, and Tuckernuck. Nantucket alone has 620 acres of sandplain grassland. This habitat supports one of the highest concentrations of rare and endangered species in the Commonwealth and is, in fact, an endangered habitat as opposed as an endangered species. Scientists and naturalists in the ecology and conservation biology fields have started to concentrate on the preservation of ecosystems as the best method to preserve and protect endangered plants and animals and the functions associated with these habitats. Studies are being done to determine a regimen for maintaining the remaining sandplain grasslands using methods such as controlled burning, mowing, brush-cutting, grazing, and harrowing. Foot and vehicle traffic is damaging to these rare communities.
In 2007, over on Martha’s Vineyard, scientists from the Marine Biological Laboratory and the Nature Conservancy started work to restore Bamford Preserve from its use as a agricultural area back to a diverse sandplain grassland capable of sustaining harriers and hawks. Sandplain grasslands are characterized as having nutrient poor soil and the addition of fertilizers to agricultural fields tends to favor non-native plants instead of the tough plants that thrive in salty, less fertile maritime soils. Converting a fertilized and heavily tilled field back to sandplain grassland can take several years.
Sandplain grasslands also support a variety of wildlife including moths, butterflies, rodents, and raptors such as short-eared owls and Northern Harriers. Unfortunately, here on Nantucket we have lost one of the denizens of sandplain grasslands, the Regal Fritillary butterfly, when hurricane Bob (1991) managed to wipe out a remnant population that had existed for many years, but which was in precipitous decline. The Northern Harrier (Circus cyaneus), also called the marsh hawk, seems to be rebounding on Nantucket with several nests active this year, and 50-55 nesting pairs identified by Dr. Rhys Bowen in previous years, making Nantucket one of the largest population sites in the Northeast. The northern harrier is a federally endangered species, easily identified by a white bar across the rear feathers. This raptor feeds on meadow voles and other rodents who will colonize sandplain grasslands. Much of the initial restoration efforts were designed to provide habitat for marsh hawk foraging. In 1996, the Partnership for Harrier Habitat Preservation (PHHP) was formed by island conservation groups to develop a large-scale vegetation management program aimed at restoring greather than 373 hectares of grassland to create and sustain habitat for Northern Harriers through prescribed burning and mechanical restoration (see the link from the Nantucket Conservation Foundation at the end of this article for more information).
On Nantucket, several conservation groups have extensive programs to protect and maintain our sandplain grasslands. The largest effort underway is conducted by the Nantucket Conservation Foundation (www.nantucketconservation.org). Mowing, controlled burns, and controlled grazing by sheep are the various methods used and researched by the NCF. Fire keeps the sandplain grassland habitat open and prevents trees and woody shrubs from taking over the open meadow. Some grassland species actually depend on the heat of the fire for their survival. Fire also replenishes the soil by releasing nutrients back into the surface layers. Originally, these habitats may have been created by natural fires caused by lightning and the combination of our poor soil and salty air. The Wampanoags on island continued to preserve the sandplain grasslands by setting fires. The NCF acts in tandem with the Nantucket Land Bank, Massachusetts Audubon Society, the Nature Conservancy, and the Land Council, among other groups to conduct prescribed burns to maintain this habitat. The Madaket Land Trust has been using brush-cutting on their properties as a land management tool and for habitat restoration (http://www.madaketlandtrust.com/projects/brush.html).
Interestingly, a dissertation by Andrea Stevens (“The paleoecology of coastal sandplain grasslands on Martha’s Vineyard, Massachusetts - UMass Amherst”) in 1996 discovered that the sandplain grasslands had existed before Europeans arrived and began farming, and grazing sheep, which indicated that burning from Native Americans played a large part in the creation of the vegetation. Paleoecology delves into the vegetation history of an area through the use of soil cores which are sifted for pollen, charcoal and seeds and dated using a variety of radionuclide dating and forensic dating techniques. Deeper cores would indicate if the habitat existed prior to any anthropogenic (man-made) intervention, which is certainly plausible considering natural fire occurrences.
Livestock grazing by the early settlers also kept down the growth of woody plants, and helped the survival of sandplain species. Close to 15,000 sheep were spread across Nantucket by 1845; their grazing created a cultural landscape that favored the preservation of the rare plants and animals associated with sandplain grasslands. In 2005, the NCF reintroduced sheep grazing to their repertoire of habitat conservation practices to control the expansion of woody species. In addition to the consumption of above-ground plant material, sheep disturb the roots and soil with their hooves, creating ideal sites for the germination of grassland-associated species. These effects, along with variations in grazing patterns over time, are hard to reproduce with brushcutting and/or prescribed burning treatments. The scientists and interns at the NCF, led by the Manager of the Department of Science and Stewardship, Karen Beattie, established several research plots to monitor pre and post treatment of vegetation by mowing, prescribed burns and grazing to establish how each plot surveyed changes vegetatively. The NCF conducts a total of 6-8 research projects each year to evaluate the success of land management techniques and the current populations and distribution of endangered harriers and plants associated with the sandplain grasslands (http://www.nantucketconservation.com/ click on Science and Stewardship – Current Research). But it doesn’t take a scientist to appreciate the natural beauty of these habitats or the incredible opportunity we have to see them. Make sure when you are visiting these areas not to disturb any of the vegetation plots and to tread lightly and stay on the trails.
