Introduction



     Three distinct regions make up the Oregon Coast. The South Coast is a mostly mountainous expanse comprised of sea cliffs and sandy beaches. Sea cliffs, terraces, and bays dominate the Central Oregon Coast. The North Coast is known for its steep-walled cliffs of Columbia River Basalt interspersed with long stretches of sandy beaches and spit-formed bays. Along the North Coast are the dune ridges of Clatsop County, which extend from Seaside and continue up to 13 miles to the north, nearly contacting the Columbia River. Within the dune system lies Sunset Beach State Recreation Site. Sunset Beach is 8.8 miles north of Seaside and directly east of Cullaby Lake. All of the observations on European Beachgrass were done at this beach.



Data/Observations



     The sand dunes at Sunset Beach are covered in a green blanket of European Beachgrass as far north and south as one can see from the beach. The invasive grass extends down to the bottom of the foredune and is distributed entirely over and behind the dune. However, no grass is seen on the gently sloping beach. As one walks toward dune 2, the Beachgrass still dominates while stout coniferous shrub-like trees about six feet tall dot the windward side of the dune. Large conifers upwards of 30 feet tall are mixed in with the small-statured trees. The ecocline from an area completely dominated by European Beachgrass to one dominated almost entirely by conifers is 200 feet, with smaller shrubs mixing with Beachgrass in-between. The grass has a spaced appearance in the conifers, seeking out ground to take root in between the trees. The conifers continue up dune 3, eventually giving way to a residential neighborhood and Sunset Lake. In summary, the Beachgrass is most dense on dune ridge 1 and abruptly decreases in density as one moves away from the ocean and into the conifers, which end suddenly on the windward side of dune ridge 3.

      Observing the dispersal of Beachgrass on dune ridge 1 reveals a very thick distribution broken up by bare patches of sand. In a few areas, the sand is barely visible when looking down. However, most areas examined revealed a patchy to uniform distribution with the sand still visible below.

      The European Beachgrass was anywhere from one foot to three feet tall and possessed dense, thick blades. The grass stood mostly erect, only gently curving over, and was able to withstand the gusts of strong wind without blowing over entirely. Instead of each stem of grass having its own root system, the Beachgrass had a rhizomal root structure, sharing the rhizome with as many as eight other stems. The rhizome was anchored firmly in the sand and was difficult to pull out. Therefore, one could speculate, there were more stems attached to the rhizome.

      Throughout the spread of Beachgrass were various patches of seeding stems. These stems were mostly concentrated about 15 feet from the terminal line of grass that meets the beach. The Beachgrass, from the beach terminus to the seeding grass, was not seeding and appeared to be this season’s growth.



Discussion



      European Beachgrass is an invasive perennial grass brought over from Europe to Western North America in the nineteenth century in order to stabilize shifting dunes. The first planting was in Golden Gate Park in San Francisco. Announced as a success, it was planted up and down West Coast dunes, particularly in Oregon (Pickart, 1997). The stabilizing grass also served to keep sand from blowing in estuaries stocked with Salmon (Dolan, 2006). Due to its invasive nature of creating monotypic stands, local species are now being outcompeted and many natural dune communities are suffering (“Ammophila arenaria,” 2010).

     As one stands on dune ridge 1 and looks toward dune ridge 2 and 3, the reason for the transition between the Beachgrass and the conifers becomes apparent. Dune 1 is the foredune and relatively young compared to all the other dunes. Dune 2 is a surface stabilized dune consisting of a thin layer of soil with loose sand underneath. Beachgrass doesn’t need any soil to take root in and can root in the sand of dune 1. While trees and shrubs need some soil to root down in and absorb the nutrients they need.

     The boundary between the grass and the conifers represents the line between a stable and unstable environment. Beachgrass is an r-selected species, meaning it is a successful colonizer and propagator. r-selected species colonize recently disturbed environments and are short-lived. They usually facilitate intermediate species and k-selected species (long-lived), which come in after the environment is stable. The foredune of the Clatsop dune system is inundated with Beachgrass, because of the fluctuating temperatures, shifting wind directions, and blowing sand that make for an unstable beach environment. Dune ridge 2 to 5 are sheltered from some wind, blowing sand, and are not exposed to the crashing waves so are able to provide a more stable environment for the accumulation of soil and k-selected species.

     In the winter, the beach is covered with water, while waves crash directly below the foredune. The new growth that is taking place several meters up the fore dune can be explained by the winter waves washing away and depositing rhizomes in this zone. This process also explains one way (besides through seeds) that Beachgrass is able to travel down dune systems.
A main problem with the invasive Beachgrass lies in its evolutionary history. It has evolved in unstable environments and found ways to take root in the loose sand without being blown away. The consistent winds of the beach keep the grass from reaching taller than 3.9 feet. However, the grass takes on an underground rhizomal structure, growing extremely fast (7 feet in six months) and sending up over 100 shoots per season (“Ammophila arenaria,” 2010).

     These structures can break off, remain viable, and establish themselves in a new area, as described above (Pickart, 1997). As more rhizomes grow, the complex becomes more interlinked and more secure. Consistent burial of the grass encourages new rhizomal structures to develop (Pickart, 1997). The deep root structure and underground spreading of Beachgrass has “locked” the Clatsop foredune in place causing a cessation of growth unlike any active and healthy foredune. Beachgrass inundated dunes are also excellent sand accumulators and tend to over-steepen the faces making it more difficult for sand to accumulate on the dunes behind the foredune (Pickart, 1997).

     Understanding how the ecology of European Beachgrass interacts with the geology of the dunes is important if we want to win the battle against the invasive grass. Many efforts have been put forward to eradicate European Beachgrass throughout the Pacific Northwest. Manual control, mechanical control, and chemical control have all been used in different areas to various degrees with no complete success (Pickart, 1997). It is possible that a highly effective method of removal will one day replace old techniques and the dunes of Clatsop County and other dunes along the Pacific Northwest coast will be revegetated and restored to their natural communities.