A phytosociological survey of the halophytic vegetation of North America's temperate-boreal Pacific coast

Questions: What is the floristic composition of the plant communities that inhabit the coastal salt marshes and adjacent wetlands of the temperate-boreal Pacific coast of North America? What are their ecological relationships in the zonal and successional gradients typical of coastal marsh systems? Does climate affect the latitudinal distribution of the azonal vegetation? What other environmental factors influence their distribution on the regional or local scale? What is the syntaxonomical framework of the communities analyzed? Study area: Pacific coast of North America between Oregon (42 degrees 05'N) and Alaska (61 degrees 30'N). Methods: Fieldwork was based on a set of 458 phytosociological releves obtained by sampling 94 sites. In all localities, zonation was interpreted by considering transects from the shoreline inland. Through traditional phytosociological tabular classification, average linkage clustering and fidelity calculations, releves were syntaxonomically classified. Syntaxa are described and interpreted according to their phytogeographical distribution, their relationships with macrobioclimates and bioclimates, and to the topographic and ecological gradients typical of coastal marshes. In order to compare the results of the European phytosociological classification with the American classification system, a crosswalk between units of the US National Vegetation Classification and syntaxa, and a key to the halophytic associations of western North America were performed. Results and conclusions: We describe the zonation of salt marshes and define the optimum zones for several helophytic and halophytic plants and communities. Despite being presently considered a type of azonal vegetation, supralitoral halophilous communities show clear relationships with the zonobiomes. Plant communities detected were finally ascribed to four classes (Asteretea tripolii, Juncetea breweri, Phragmito-Magno-Caricetea and Spartinetea maritimae), seven orders, eight alliances and 15 associations. Fourteen new syntaxa are described and typified according to ICPN: Caricetum lyngbyei, Caricion lyngbyei, Jaumeo carnosae-Sarcocornietalia perennis, Jaumeo carnosae-Sarcocornietum perennis, Jaumeo carnosae-Sarcocornion perennis, Potentillo pacificae-Calamagrostietum canadensis, Potentillo pacificae-Deschampsietum beringensis, Puccinellietum andersonii, Puccinellietum nutkaensis, Puccinellion nutkaensis, Sarcocornio perennis-Deschampsietum beringensis, Schoenoplectetum americani, Triglochino maritimae- Plantaginetum juncoidis and Triglochino maritimae- Sarcocornietum perennis.