Woods Hole Research Center

 

Major Dune Systems

Major dune systems are harsh environments, formed by wind, and characterized by having both primary and secondary dunes and dune bogs. Mounds of sand are stabilized by vegetation, and slowly built into a dune by the wind.

Significant dune migration occurs by the wind picking up sand grains from the dune's windward base and bouncing the grains over the crest to the leeward side, in a process called saltation. The dune's windward base may be eroded down to the point where it is intersected by the water table. Here, in wet months, pools may form, which are quickly colonized by cranberries (Vaccinium macrocarpon), sedges and wildflowers. This region is the dune bog, and it provides an unusual habitat for many types of wildlife.

Dunes are stabilized by vegetation, but poor land-clearing and agricultural practices over the last three centuries destroyed much dune vegetation, thus letting wind reach the sands. Eventually, these cleared dunes were recolonized by grasses, and succession has led to the pitch pine forests of today.

There are five major dune systems on Cape Cod: the Provincelands in Provincetown and Truro, Sandy Neck in Barnstable, Monomoy Island in Chatham, Chapin Memorial Beach in Dennis, and Chapoquoit Beach in Falmouth.

Plants and animals found in dune habitats may be hurt or killed by foot traffic and off-road vehicles.

 

Barrier Beaches

Barrier Beaches are dynamic strips of coastal dunes and beaches that are formed by long shore currents depositing sand across the mouth of an inlet or harbor. Barrier beaches are divided into frontal beach, dune, and inland beach, usually with a marsh or estuary system in the sheltered zone behind the barrier. These beaches are extremely dynamic systems that are constantly subjected to wind and wave energy. Well-vegetated areas on the barrier are somewhat stable, but sandy areas migrate significantly and large storms can rip holes right through the barrier. Inland areas are buffered by the barrier beaches, which dissipate storm wave energy by their shifting sands.

Barrier beaches provide nesting sites for certain rare species of birds including piping plovers (Charadrius melodus) and roseate terns (Sterna dougallii).

Barrier beaches are too unstable to build on, and yet many people do just that. Any structure, whether a house or a jetty, that impedes the movement of a barrier beach will cause undesirable changes in the beaches ability to dissipate wave energy. No structure is permanent if built on a barrier beach.

 

Critical Woodland Communities

The Forests of Cape Cod, which Native Americans had maintained with sporadic fires, were rapidly cut down by the first European settlers. Areas of forest were harvested for lumber and fuel, and cleared to make room for agriculture. The thin layer of topsoil quickly eroded into the sea, and large areas of the outer Cape, including Eastham and Orleans, were transformed into massive sand dunes.

Many hardwood stands were also destroyed in large fires that used to sweep across the Cape, but improvements in infrastructure and fire-fighting techniques finally ended the forest fires.

Today, the Cape is dominated by pitch pine/oak forests, which are the pioneer tree species that recolonized the cleared land. However, a few hardwood stands do exist, representing more advanced stages of succession. These stands are young and rare, found in uncleared areas missed by fires, and characterized by having fairly rich soils.

Stands of native trees that can be found on the Cape include: American holly (Ilex opaca), coastal basswood (Tilia neglecta), American beech (Fagus grandifolia), yellow birch (Betula alleghaniensis), black birch (Betula lenta) and post oak/hickory associations (Quercus stellata/Carya spp.).

Development is a major threat to the few remaining hardwood habitats.

 

Pitch Pine / Scrub Oak Barrens

These barrens are dry pitch pine (Pinus rigida) forests with acidic, sandy, nutrient-poor soils, open canopies and dense understories of scrub oak (Quercus ilicifolia). Unlike the majority of Cape forests, tree oaks do not co-dominate these areas. Instead, open areas have bearberry (Arctostaphylos uva-ursi), sedges (Carex spp.), lichens (Caladonia spp.), and broom crowberry (Corema conradii).

Pitch pine/scrub oak barrens are fire-maintained communities in which nutrients are released in ash. Succession by hardwood tree species is prevented by periodic burns. These communities survive moderate fires very well, and species diversity is greatest in the years after a burn.

Large pitch pine barrens are mosaics of small habitats, often containing kettle holes dominated by low-growing heaths. Barrens support different plant and wildlife populations than denser pitch pine/tree oak forests do, and moths especially flourish in barrens. The barrens buck moth (Hemileuca maia) is only found in pitch pine/scrub oak barrens. These barrens are often in areas desirable to developers, because the topography is well-suited to construction. Large barrens are subdivided by development, thus decreasing species diversity, which is highest in large tracts. With development comes fire suppression, which ends the burns so critical to pitch pine/scrub oak barren maintenance.

 

Sandplain Grasslands

Sandplain Grasslands are globally rare areas dominated by two bunch grasses, little bluestem (Schizachyrum scoparium), and poverty grass (Danthoria spicata). Between the grass tussocks a diverse and unusual plant community thrives, including sandplain gerardia (Agalinis acuta), a federally endangered plant found at two sites on Cape Cod. The presence of bird's foot violet (Viola pedata) indicates a healthy grassland.

Sandplain grasslands are transient communities that quickly colonize cleared areas, and then quickly succumb to succession by shrubs. Since open areas on the Cape are subject to development, these grasslands are commonly found in maintained clearings, such as along roadways or under powerlines.

Studies are being done to determine a regimen for maintaining the remaining sandplain grasslands with methods of controlled burning, mowing and grazing. Foot and vehicle traffic is damaging to these rare communities.

 

Heathlands

Heathlands are nationally significant communities dominated by dense mats of prostrate shrubs that hold the sandy soils and prevent erosion. On Cape Cod, heathlands are now found mostly in small open areas between Eastham and Truro, and in protected stretches along the Cape Cod National Sea Shore.

This habitat was probably more prevalent in previous centuries, when deforestation was at its peak, but now few areas suitable for heathland establishment are being formed. Coastal heathlands are stable communities that are adapted to the harsh seaside conditions. Here, wind and salt spray preclude invasion by taller trees.

Inland sites are transitional communities that may develop in any cleared area, but are able to survive only in maintained clearings, such as along roadways and powerlines. Inland heathlands generally have higher diversity than coastal sites.

Coastal sites are dominated by bearberry (Arctostaphylos uva-ursi), beach heather (Hudsonia tomentosa), and black huckleberry (Gaylussacia baccata), while at inland sites beach heather is typically replaced by golden heather (Hudsonia ericoides). Bushy rockrose (Helianthemum dumosum) and broom crowberry (Corema conradii), a species of special concern, may be found in all heathlands. The Hudsonia genus plants are not true heathers but belong to the Rockrose Family (Cistaceae).

Heathlands are regularly lost to development.

 

Grassy Heaths

Grassy heaths are globally rare assemblages of sandplain grassland and heathland species, with neither association being dominant. The total range of these habitats is mostly restricted to Nantucket and North Truro, and the Cape's two largest grassy heaths are on Corn Hill and Lookout Bluff in Truro.

The formation process of these habitats is unclear, but grassy heaths may be an intermediate stage between sandplain grasslands and heathlands.

Rare species that are commonly found in grassy heaths are: purple needle grass (Aristida purpurascens), Commons' panic grass (Dichanthelium ovale), Eastern spadefoot toad (Schaphiopus holbrookii), and chain dot geometer moth (Cingila catenaria).

These habitats are easily damaged by vehicle traffic and development. Quite recently, grassy heaths have been destroyed in Truro, and houses built on the sites.