management implies the management of social and economic, as well as 

 natural, systems. (J.B.) 



Keywords: coastal marshes, conservation, planning and management, 

 Chesapeake Bay 



B. Marsh Grass Productivity Studies 



II-B-1 



Eilers, H.P., III. 1975. Plants, plant communities, net production and 

 tide levels: the ecological biogeography of the Nehalem salt marshes, 

 Tillamook County, Oregon. Ph.D. Thesis. Oregon State University. 

 387 pp. (Diss. Abstr. 35:5851-B) 



Nehalem Bay is located on the northern coast of Oregon in Tillamook 

 County and contains approximately 243 ha of salt marsh. The Nehalem 

 marshes occur as islands and land-tied units. West Island is the 

 largest marsh island with an area of 82.9 ha and a maximum elevation 

 of 3.079 m above mean lower low water (MLLW). Three divisions on 

 West Island, based on inundation period, have been identified: intertidal 

 marsh, below mean high water (MHW); transitional marsh, from MHW to 

 2.76 m above MLLW; and extratidal marsh, above 2.76 m. West Island may 

 be further subdivided into four topographic units based on the steepness 

 of the elevation gradient: edge marsh, from the lower margin to 

 2.00 m; low marsh, 2.00 to 2.36 m; transitional marsh, 2.36 to 2.76 m; 

 and high marsh, 2.76 m and above. 



Creek density is low for the lower intertidal marsh for the edge 

 marsh, and for the higher extratidal marsh and is high for the upper 

 intertidal and transitional marsh. Salt marsh vegetation on West Island 

 was sampled by harvesting above-ground biomass along seven transects 

 at two-month intervals from May 1972 to September 1972. Plant species 

 diversity increased with elevation and each species displayed a particular 

 elevation range. Analysis of dry-weight data by an ordination routine 

 suggested the presence of 11 plant communities along the elevation gradient 

 on West Island. 



Plant communities named by dominant species are Triglochin , Scirpus , 

 Carex (tall and short phases), Carex-Deschampsia-Triglochin , Triglochin- 

 Deschampsia , Carex-Deschampsia-Triqlochin-Agrostis , Juncus-Agrostis , 

 Juncus-Agrosti s-Festuca , Aster-Potentilla-Oenanthe , Carex-Aster-Oenanthe , 

 and Picea-Salix . Plant communities are readily identified by signatures 

 on aerial photographs. Net areal production on West Island increased 

 with elevation and varied from a minimum of 518 g/m^/yr for the 

 Triglochin community to a maximum of 1936 g/m^/yr for the Aster-Potentilla- 

 Oenanthe~cbmmu n i ty . 



33 



