Sand dunes are found along the coasts of most of the large land
masses of the world. Because of their proximity to man and his
activities, the maritime sand dunes of Europe, particularly Germany,
France, Holland and Scandinavia, have the longest history of stabilization
activities and botanical investigation. There are coastal dune
areas, some of great extent, in Africa, tropical Asia, Australia, and
South America. In general, little published information is available
concerning these areas. Ecological studies of coastal dune vegetation
and environment have been most extensive in Great Britain, and
to a lesser extent, in North America.
Of the North American coastal dunes, those of the east coast
have received considerable attention while those of the west coast
have been largely neglected. Along the Oregon coast are found some
of the most extensive and best developed coastal sand dune areas in
North America. Occurring on some 225 km. of the state's 500 km. of ocean facing coastline, these areas are made up of a great variety
of dune landscape features and present unique conditions for the development
and maintenance of vegetation.
There are many places in this dune area where the strong,
constant winds have eroded the sand surface to or near the water
table resulting in a stabilized surface - the deflation plain - which
provides an excellent starting point for the development of vegetation.
After preliminary ground and air reconnaissance, 11 deflation plains
were selected for detailed study, ranging in location from Sand Lake
on the north to Tahkenitch Creek on the south. These deflation plains
and their location are described in detail.
Vegetation data (species and cover) were taken on a total of 134
sampling stands, each consisting of five meter-square quadrats for
herbaceous vegetation, and one 6 x 6 meter quadrat for shrub and
forest vegetation. The species and stand data we arranged on comparative
charts so as to bring together stands with mutually occurring
species. This resulted in the delineation of seven communities
with definite successional relationships. Primary succession begins
with one of four herbaceous communities: dry meadow, meadow,
rush meadow or marsh. Succession then proceeds to low shrub,
tall shrub and finally forest.
The dry meadow is dominated by three species: Lupinus
littoralis, Ammophila arenaria and Poa macrantha. The site is dry with no standing water at any time. Sand deposition and deflation
occur in varying degrees. The important species of the meadow are
Festuca rubra, Aira praecox, Hypochaeris radicata and Fragaria
chiloensis. The surface is dry except for short periods of standing
water during the winter months. There is no sand deposition. The
rush meadow is characterized by its dense growth of Trifolium
willdenovii and Juncus phaeocephalus. The site is low and moist,
with water standing on the surface during the winter months. The
marsh is found on areas which are quite damp-water stands on the
surface for around six months of the year, and is just below the
surface for the remainder of the time. It is made up of dense stands
of Carex obnupta and Potentilla anserina.
The low shrub community is an open stand of Salix hookeriana,
Gaultheria shallon, Vaccinium ovatum and Myrica californica. This
develops into a tall shrub stage which is frequently an impenetrable
thicket with increasing dominance of seedlings of Pinus contorta and
Picea sitchensis. Development of a forest of Pinus and Picea is very
rapid. If the area is free from disturbance long enough, the shorter
lived Pinus dies out, leaving a forest of Picea.
The deflation plains represent only part of the many aspects of
the total dune landscape still awaiting investigation. The increasing
importance of the Oregon coastal dunes to industry and recreation
make imperative the initiation of long term ecological studies
