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Cranberry Lake/West Beach Sand Dunes: Deception Pass State Park—February 2005

By Brenda Senturia

The Oregon Coast may be famous for its sand dunes, but Puget Sound boasts a nice dune remnant at Cranberry Lake/West Beach in Deception Pass State Park. Sand dunes are a dynamic interaction of wind, water, sediments, and vegetation and form where these elements meet sufficient flat topography. While fairly stable, all stages of dune succession may be seen here, from bare sand to mature forest. Dunes often dam freshwater lakes. Begin the walk at Cranberry Lake, now dammed by the parking lot. Walk south on the paved 0.7 mile dune trail, just past the West Beach restrooms.

Dune pioneers must cope with blowing sand, which can both bury, and scour, lack of nutrients and moisture, and salt spray. Note the sand-crusted leaves of yellow sand verbena (Abronia latifolia) and the mostly buried leaves of beach silvertop (Glehnia littoralis) forming tiny mounds in areas of mostly bare sand. Deep taproots help hold the plants in place and reach the water table which can be three or more feet under the surface. The thick taproots also store energy the plants can use to grow when buried by sand. Fleshy glandular or hairy leaves also help conserve moisture and protect from wind, salt, and sand. Beach knotweed (Polygonum paronychia) has woody stems for protection and leaves with margins rolled under to reduce surface area and prevent excessive moisture loss. The branched, trailing knotweed also helps bind sand.

Major stabilizers of sand are American dune grass (Elymus mollis) and large-headed sedge (Carex macrocephala). Both plants have vigorous underground rhizomes and cover large areas. The sedge grows close to the ground where wind is less extreme, and has large seeds, spread by wind, but big enough to stay lodged in blowing sand. The taller dune grass provides cover for animals such as the rabbits whose scat accompanies and feeds it.

These pioneers moderate the climate where they grow, providing cooling, moisture conserving shade, blocking wind, and they add organic matter to the soil. These less harsh conditions suit a number of plants, including yarrow (Achillea millefollium), and bracken fern (Pteridium aquilinum). These newcomers eventually outcompete the pioneers and create conditions suitable for shrubs such as Nootka rose (Rosa nutkana) and salal (Gaultheria shallon). Young shore pine (Pinus contorta) and Sitka spruce (Picea sitchensis) grow out of the now humus-rich soil of these communities.

Forested dunes near the surf are covered with dwarfed shore pine, Sitka spruce, and Rocky Mountain juniper (Juniperus scopulorum). Lee of these forested dunes, there are areas of moss-covered sand. Kinninnik (Arctostaphylos uva-ursi) seedlings are favored in the environmental conditions of the moss carpet. Luxuriant mats of kinninnik border the trail as it heads east into mature forest bordering Cranberry Lake. Tall, wind-sculpted Douglas-fir (Pseudotsuga menziesii) line the forest edge, while upright Douglas-fir, western hemlock (Tsuga heterophylla), Pacific yew (Taxus brevifolia), salal, oceanspray (Holodiscus discolor), and birdsong fill the forest interior.

Wind can scour sand away on the lee side of dunes down to the water table, creating moist deflation plains. An unfortunate picnic table rots in one such plain, surrounded by slough sedge (Carex obnupta) and red alder (Alnus rubra). Slough sedge grows with Hooker’s willow (Salix hookeriana) at the trail’s end, the northwest shore of Cranberry Lake.

Wind, water, and fire are the traditional agents of disturbance in dune ecosystems. Add here human disturbance, from picnic parties and children building sand castles, to curious botanists stepping off the trail; all can create new areas of bare sand for pioneers to colonize.

Allow one hour to a whole day for this easy walk. Directions: drive State Route 20 to milepost 41.3 and turn west into the Whidbey Island entrance to Deception Pass State Park. Follow signs to Cranberry Lake and West Beach.



Updated: July 3, 2016
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