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Vegetation and soil characteristics of intertidal habitats colonized by Spartina anglicain Padilla Bay, WA, USA.
Hellquist, C. Eric1, Black, R. Alan1, 1
ABSTRACT- At Padilla Bay in northern Puget Sound, USA, Spartina anglica (Poaceae), an introduced cordgrass, has become a prominent species in salt marshes and mudflats. Spartina anglica tends to colonize low intertidal zones. Middle intertidal zones of marshes are occassionally colonized by S. anglica, while high intertidal zones bordering uplands usually are not colonized. To describe soil characteristics and vegetation patterns of intertidal zones invaded by S. anglica, transects parallel to the shoreline were surveyed for soil redox potential, salinity, water content, water potential, and percent cover of vegetation. In low intertidal zones (n=191 plots) vegetation was dominated by Salicornia virginica (30%), Spergularia canadensis (10%), Distichlis spicata (5%), and Triglochin maritimum (3%). Mean soil redox potentials were negative (-116 mV, n=191) and mean soil salinities were high (42 ppt, n=170). Middle intertidal zones of marsh sites (n=71 plots) where S. anglicatends not to colonize, were dominated by Distichlis spicata (70%), Salicornia virginica (37%), Atriplex patula (3%) and Spergularia canadensis (1%). Redox potential was higher (91 mV, n=71), while soil salinities were slightly lower (40 ppt, n=55) than the low intertidal zone. Our results suggest that at Padilla Bay, S. anglica establishes among the lowest fringe of vascular vegetation within waterlogged, anoxic, and highly saline sediments and is less likely to become established within intermediate and high intertidal zones.
KEY WORDS: Spartina anglica, invasion, Puget Sound