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Coastal Dune Restoration Native Plant Restoration Overview – Coastal Dune Native Plant Restoration Ma-le’l Dunes South Spit Cooperative Management Area
Overview Coastal Dune Native Plant Restoration The coastal dunes of Humboldt Bay and its surrounding areas constitute a unique and fragile ecosystem. The 34-mile stretch of coastline encompasses an array of habitats that support a diverse group of plant and animal species ranging from dune obligates such as endangered beach layia (Layia carnosa) and Humboldt Bay wallflower (Erysimum menziesii ssp. eurekense) to transient inhabitants like gray fox and skunks. The foredunes that run parallel to the beach are one of the prevailing physical features of the dunes. The foredunes are typified by varying environmental conditions and receive the brunt of storms as they reach the mainland. Living in this sometimes turbulent realm is a diverse assemblage of plants called the dune mat that are adapted to survive nutrient poor soils and harsh maritime environmental conditions. Despite these adaptations, invasive plants such as European beachgrass (Ammophila arenaria) issue a chronic threat of displacement to this unique plant community by disrupting natural dune processes. The Arcata Field Office (AFO) is committed to dune restoration through the eradication of invasive, nonnative vegetation and monitoring of rare and endangered native plant species. The AFO has been administering recurrent restoration activities at the Ma-le’l Dunes, South Spit Cooperative Management Area, and the Samoa Dunes Endangered Plant Protection Area. Ma-le’l Dunes The 152 acre BLM Ma-le’l Dunes is composed of two parcels: the original northern parcel (112-acres) and the recently (2003) acquired southern parcel (40 acres). Combined, these two parcels contain about 50 acres of foredunes which have now been fully treated for invasive European beachgrass (Ammophila arenaria) and planted with native dunegrass. The Bureau of Land Management (BLM) has partnered with the California Conservation Corps (CCC) for the past 14 years to achieve complete removal of European beachgrass in the foredunes, thus making way for native American dunegrass (Leymus mollis ssp. mollis) recovery efforts that would complete the optimum habitat restoration scenario. The first phase of native American dunegrass reintroduction occurred in 2004 on the original parcel with about 18,000 native dunegrass rooted culms (stems) being planted. This effort followed ten years of manual European beachgrass eradication and was made possible by the National Fish and Wildlife Foundation Native Plant Conservation Initiative (NFWF NPCI), CCC, and private plant material donors. The second phase of native American dunegrass transplantation at the BLM Ma-le’l Dunes occurred in 2008 with about 8,325 native dunegrass culms being planted in the southern portion of the BLM Ma-le’l dunes. The effort followed four years of European beachgrass removal that could not have been achieved without supplemental assistance provided by the United States Fish and Wildlife Service's Humboldt Bay Coastal Program. The second phase of the American dunegrass transplantation project was achieved with labor assistance from the CCC, financial assistance from the NFWF NPCI, and cooperation from the City of Eureka and Humboldt County Parks both providing native plant materials. In total, 26,325 native dunegrass culms have been planted at the BLM Ma-le’l Dunes area.
South Spit Cooperative Management Area (CMA) In 2002, the BLM assumed the lead in cooperatively managing about 600 acres of the 800 acre, 4.5 mile long tract of land on the south and west side of Humboldt Bay known as the South Spit. At that time, there were approximately 300 acres of the South Spit that were identified as being infested with invasive weeds (predominately European beachgrass and annual grasses) and stabilized dune scrub. Since then, the BLM has eradicated European beachgrass from over 30 acres through consistent manual removal with the assistance of the CCC that has resulted in direct habitat and population increases to native and endangered plant species.
Samoa Endangered Plant Protection Area (EPPA) The 40-acre Samoa Dunes Endangered Plant Protection Area (EPPA) is located within the 300-acre Samoa Dunes Riding Area owned and managed by the BLM. The Samoa Dunes Riding Area is situated on the Samoa Peninsula adjacent to Humboldt Bay and the Pacific Ocean. The Samoa Peninsula is home to two endangered plant species, Humboldt Bay wallflower, and beach layia. The BLM EPPA hosts one of the most robust populations of Humboldt Bay wallflower on the Samoa Peninsula; however, these populations are under chronic threat of displacement from invasive weed species. The greatest displacement forces in the EPPA have come from weeds such as yellow bush lupine (Lupinus arboreus), European beachgrass, iceplant (Carpobrotus edulis), and a collection of annual grasses, particularly quaking grass (Briza major). Together, these weeds are guilty of enriching soil fertility, increasing plant competition, and displacing native species. Another species that has surfaced in the EPPA is Bermuda buttercup (Oxalis pes-caprae). In many areas of the north spit manual weed control has proven effective and sufficient to reverse the trend of habitat loss by invasive weed, however, in the EPPA this method is not enough to reclaim habitat. The EPPA is too geographically separated from the beach and does not received fresh inundations of sand necessary to maintain the semi-stabilized environment that dune obligate species are adapted to. Thus, stabilization and consequent organic matter build-up have led to conditions suitable for other invasive species that displace native species. Methods The BLM utilized heavy equipment in 2000 to remove both plant matter and the surface layer of the soil containing the weedy seed bank. The CCC hand crews were utilized as well to hand weed and remove duff in the transitions zones and margins, and among the relict natives that survived amidst the weeds. The project began by intensively flagging the area; yellow or blue flags marked native plant individuals or boundaries, and white flags marked the disturbance perimeter for the heavy equipment. A midsize excavator was used to carefully scrape off the surface debris, plant matter, and top six inches of duff. This material was placed in another weedy area. Once this pile was sufficiently large, a pit was dug to the depth of the water table with the sterile sand being piled on another weedy area. Then, the weedy pile was placed in the pit, and capped with sterile sand. Enough sterile sand was left on the surface to create some minor dune-like topography. During this process, the excavator operator was very careful not to trample any native plants. No intact dune mat areas were traversed with the heavy equipment. In preparation for the CCC hand crews, the equipment operator left small pits with a berm of sterile sand around the edge for easy burial. Hand crews used leaf rakes to re-sculpt new dunes created by the excavator. Crews of ten people or more, worked for two weeks pulling weeds, shoveling up duff and re-seeding with natives, primarily coast buckwheat (Eriogonum latifolium). The overall project took place over a period of two and a half weeks. Current Condition Since 2000, this project has been maintained by BLM staff with assistance from the CCC. Several weeds have tried to re-infest the area including annual grasses, sheep sorrel (Rumex acetosella), and Bermuda buttercup (Oxalis pes-caprae). A combination of annual hand treatment and Waipuna™ hot foam weed treatment has enabled feasible and successful maintenance of the project area.
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