Geoscience Reference
In-Depth Information
The roots of marram grass knit together the dune sands, which are vulnerable to wind and wave.
Farther away from the shore, a variety of salt-tolerant plants begin to take root on the leeward side of the
dune and on the secondary dunes that often form behind the primary one. Among them are seaside goldenrod,
common wild rose, and beach heather, which add splashes of color to the seaside scene. Eventually, soil begins
to form on the lee side of dune systems, resulting in a transition to a more terrestrial flora, with the growth of
shrubs such as northern bayberry. This shrub bears buckshot-sized fruit covered in a waxy coating favored by
birds such as the myrtle (or yellow-rumped) warbler, which takes its name from the plant, sometimes known as
myrtle. Both bayberry and beach pea are capable of nitrogen fixation, the conversion of atmospheric nitrogen
into organic nitrogen compounds. They achieve this through a symbiotic relationship with nitrogen-fixing bac-
teria. This nitrogen is key in the nutrient sustainability of the dunes.
In rare instances, a parabolic, or wandering, dune system develops. One such system is the Greenwich
Dune, now an adjunct to the Prince Edward Island National Park. This dune is moving from the tip of the
Greenwich peninsula in the direction of the maritime forest behind it. The leading edge of the dune is traveling
at the dreamlike, but inexorable, rate of 3 to 6 meters (10 to 20 feet) per year. Evidence of its travels is seen in
the skeleton forest left in its wake. The tops of white birches stick out of the sand like candelabra gracing an
immense white tablecloth. Characteristically, a parabolic dune is horseshoe shaped, with the prongs of the U
