Skip to main content

You are here

Plants

Coastal Vegetation and Plant Ecology

Though I do not believe that a plant will spring up where no seed has been, I have great faith in a seed. Convince me that you have a seed there, and I am prepared to expect wonders.   - Henry Thoreau
Maple Leaves

Maple tree (Pat Breen, Landscape Plants:
Images Identification, and Information, Volume 1,
Oregon State University Dept. of Horticulture)

Mosses hang thick on the Big Leaf Maple trees forming a tunnel over the Yaquina River. As the morning sun breaks across the stream, steam rises in slender columns from the moss, soaking every square inch of tree in moisture. Up the bank, Highway 20 runs to Newport through a similar tunnel of maple and fir. The road cuts a thin line through the dark green forest that covers this landscape. From sword ferns and salal to pitcher plants and giant spruce trees, Oregon's north coast is thick with a diversity of plant life that rivals tropical ecosystems for diversity and biomass.

Salt Marsh Plants

Salt marshes are transitional areas between land and water, occurring along the intertidal shore of estuaries and sounds where salinity (salt content) ranges from near ocean strength to near fresh in upriver marshes.

Salt Marshes

Coastal Salt Marsh
(Outdoor Fun in the Great Northwest)

Salt marsh plants, such as pickleweed (Salicornia spp.) and saltgrass (Distichlis spicata), are uniquely adapted to the fluctuating coastal salt marsh environment, where their roots take a twice-daily bath in ocean water at high tides. As these plants die and break down, their stored nutrients enter the food web and provide a continual source of food for clams, crabs, and fish. Most animal life in the salt marsh is not easily seen, but a closer look might reveal tracks left by a raccoon or black-tailed deer visiting for a low tide snack.

Salt marsh plants are important because their matted roots stabilize the shoreline and are a buffer for pollution from runoff. As rain and debris from strong winter storms courses downstream, the salt marsh acts as a sponge, where bacteria trap and break down excess nutrients, heavy metals and other chemicals from polluted runoff water. This helps protect the water quality of the bay.

Coastal Strand

These plant communities are occurring both on beaches above high tide and on sand dunes behind the foredune.

Since the establishment and subsequent naturalization of European beachgrass, this habitat has decreased as the width and height of the foredune has increased. The physical conditions of these habitats are adverse and have high substrate instability, nutrient-poor soils, a high exposure to salt spray and "sandblasting" (caused by daily northwesterly winds) which leads to a shifting, sandy substrate.

Vegetation on beaches is generally low in species richness and plant cover. On most beaches typically only 2-3 species (such as Cakile ssp., beach bursage, and yellow sand-verbena) are present on the ocean side of the foredune. These species are typically herbaceous perennials (the exception is Cakile) which are evergreen, succulent, and prostrate. Many of these species are early colonizers which begin sand stabilization. Seed production is typically low as the majority of these species disperse by rhizomes or stolons. Seed dispersal is primarily by wind and possibly by tides. Yellow sand-verbena fruits have small wings which aid in dispersal along the beach. In some cases (although undocumented) long-distance dispersal may be caused by seeds being swept into the tide and being deposited on another beach.

Historically, (pre-European beachgrass) beaches had a low foredune, which rose gradually from the beach. The foredune consisted of rounded mounds caused by the native sand stabilizing plant species. The dominant species included American dune grass (Leymus mollis ssp. mollis), yellow sand-verbena and beach bursage. This pattern resulted in a series of dunes alternating with swales which were oriented perpendicular to the coast (that is, aligned with the prevailing onshore winds). Very few of these low, mounded foredunes remain along this section of coast, with the exception at river mouths. With the establishment of European beachgrass, these rounded dunes have been replaced by a steep foredune and inland dunes oriented parallel to the coast. European beachgrass may reduce native species richness by up to one half. This decline has resulted in many of these plant communities being threatened (although most of the plant species are relatively common).

European beachgrass deserves special attention due to its impact on vegetation along the Pacific Coast. It was first introduced to North America in 1869 at San Francisco. Extensive plantings occurred on the Oregon coast from the 1930s to 1950s. It now occurs from the Queen Charlotte Islands south to southern California. European beachgrass grows best in areas where sand accretion is greatest (windward side of dunes). When established, the plants develop a vigorous rhizome system, both horizontal and vertical. Under conditions of heavy sand accretion many new shoots arise from the nodes of the vertical rhizomes, thus creating hummocks. Although the plants produce numerous seeds, very few of these survive. It appears that conditions along the Oregon coast, such as strong onshore winds, moderate year round temperatures, ample rainfall and an abundant sand supply favor the growth of European beachgrass. Many efforts have been made in recent years to control European beachgrass in certain areas, all with little success. Methods have included herbicides, burning, tilling, salt-water irrigation, and manual removal. It appears the best method may be a combination of two or more of these methods over a long period of time.

As a result of dune stabilization, many of the plant species occurring on the dunes are introduced species. These include; sweet vernalgrass (Anthoxanthum odoratum), ripgut brome (Bromus diandrus), hairy cat's-ear (Hypochaeris radicata), and in this area, gorse (Ulex europaea). These and other exotic species make up a large proportion of the vegetation on most of the sand dunes in the area.

Deflation Plain

Behind the foredune is the deflation plain, which is formed when sand is eroded away to the water table. Since the establishment of European beachgrass the deflation plain has steadily increased in width. Species present in these communities include many species of sedges (Carex ssp.), rushes (Juncus ssp.) and spike rushes (Eleochaeris ssp.).

Coastal Headlands

Coastal headlands are dominated by evergreen shrubs, usually less than 2 meters tall, and wind pruned tress. Species include coyote brush (Baccharis pilularis), salal, black crowberry (Empetrum nigrum), common juniper (Juniperus communis), hazel nut (Corylus cornuta), black twinberry (Lonicera involucrata), and wax myrtle (Myrica californica). Herbaceous species include reed grass (Calamagrostis nutkaensis), frosted paintbrush (Castilleja affinis var. littoralis), and Bolander's sneezeweed (Helenium bolanderi). These plant communities endure very harsh environmental conditions including, strong winds, year round salt spray, and fog.

Coniferous Forests

Coniferous forests in this region occur on soils ranging from stabilized sand to soils on old marine terraces. These forests are primarily composed of shore pine, Sitka spruce (Picea sitchensis) and, in more protected areas, Douglas-fir (Pseudotsuga menziesii var. menziesii) and western hemlock (Tsuga heterophylla). These coastal forests have a dense understory composed of many shrubs such as rhododendron (Rhododendron macrophyllum), salmonberry (Rubus spectabilis), black twinberry, and wax myrtle. Aerial photographs from the 1940s and 1990s show that these forests have become more abundant on sand dunes. This is probably a result of the establishment of European beachgrass which has caused secondary succession to occur more rapidly by removing the historical disturbance factor (moving sand).

pitcher-plant

Pitcher plant
(Barbara Logan, 1991)

Freshwater Wetlands

These habitats include deflation plain wetlands, sphagnum bogs, and lakes formed by small creeks that have been blocked by moving sand dunes. Sphagnum bogs typically occur in depressions and in coastal headlands with Blacklock soils where water is "perched." Species present in these communities include pitcher-plant (Darlingtonia), russet cottongrass (Eriophorum chamissonis), yellow pond-lily (Nuphar luteum ssp. polysepalum), and bladderwort (Utricularia vulgaris).

Sources

California Natural Resources. California Natural Resources Agency.

Bruce Rittenhouse, Botanist, Coos Bay District BLM.

United States Environmental Protection Agency. Coastal Watershed Factsheets - Estuaries and Your Coastal Watershed. EPA 842-F-98-009. July 1998.

Oregon Coastal Atlas. Learn from the Oregon Coastal Atlas. Resources and News. International Coastal Atlas Network.

Compiled by John Ame, Science Writer (2007)

randomness