Hawksnest Pond was formed when the retreating glacier left behind a huge block of ice, half-buried in the sand. When the ice melted, it left a large depression called a kettle pond, or a coastal plain pond. A coastal plain pond is one of the rarest wetland types in North America.
The plants growing along the sandy shore of Hawksnest Pond together make up the Coastal Plain Pondshore Community. We'll call it the Pondshore Community for short. It's composed of a mixture of herbaceous and grass-like plants, growing between the shallow water and the shrubs that surround the pond.
They grow in soil ranging from patches of sand, sandy or muddy peat, to cobbles.
The pondshores in the Six Ponds District of Harwich are considered an "imperiled plant community" by the State. Not only is this plant community home to several rare species, but it also helps safeguard the pristine water quality of Hawksnest.
Not only do the water levels change through the year, but between years as well. Only one year in about 5 may be dry enough for the community to develop fully. The lowering of water levels during the growing season is probably the single most important factor in providing suitable habitat for the plants of the Pondshore Community.
The periodic flooding of the shore also helps to keep out shrubs and upland plants, and the periodic drying keeps out aquatic plants.
Characteristics of the community
The Pondshore Community contains a number of plants which seldom occur elsewhere. Some may be locally abundant, mixed in with more common marsh emergents such as rushes, sedges, Boneset and Purple Gerardia.
The plants of the community appear to form zones between the water and the shrubs around the pond. The driest zone, inundated only in the highest water, may have New England boneset* or Maryland meadow-beauty, both considered rare in Massachusetts. The higher shoreline is home to Thread-leaved sundew (common on these ponds but uncommon elsewhere), and Spatulate-leaved sundew. The mid to upper level is home to redroot (a species of special concern) found in the Six Ponds District.
Threats and Management
Pondshore Communities have several threats caused by human disturbance. The community requires natural fluctuation of the water levels along the shore. Artificially maintained high water levels reduce the area of shore available for the Pondshore Community. Most of the plants of the community can withstand high water for a few years, which happens naturally, but most need to be out of water to reproduce.
Human use of the pondshores, including walking, offroad vehicles, and beach building, restricts plant growth. Experiments have shown that a few walking trips can create a trail where no plants grow. In areas of heavy use, the plants of the Pondshore Community can easily be eliminated.
Nutrient enrichment from septic systems poses a serious long-term threat to the natural balance** of ponds. This can change the character of the ponds, allowing algae and pondweeds not native to the ponds to grow and reduce the habitat available to the plants of the Pondshore Community.
Excessive drawdown from pumping at town wells reduces natural fluctuations and allows woody species to advance down the shores.
Gallery of members of the community
** The upset in natural balance of ponds from too many nutrients, causing fast "aging" of the pond and blooms of toxic algae, is called "eutrophication."
This article is quoted and condensed from a fact sheet.
You can find a list of rare species for Harwich here.