3.3.2 Plant Community 
Vegetation data were collected from both a quadrat and along a transect at each 
site, and data from these two approaches are presented separately. Vegetation percent 
cover, maximum plant height (emergent macrophyte) or leaf length (seagrass), and 
biomass of each taxon were recorded from each vegetation quadrat. Only vegetation 
percent cover was estimated along each transect. 
Quadrat Species Assemblages and Percent Cover 
Vegetation was present in the quadrats at 150 of the 217 sites sampled. The 
types of vegetation recorded within the quadrats included 28 emergent macrophytes, 2 
seagrasses, and macroalgal taxa (Appendix Table 4). Three emergent macrophytes, 
Cotula coronopifolia, Lepidium latifolium, and Spartina alterniflora, are nonindigenous 
species. Two species of seagrass, Zostera marina and Z. japonica (nonindigenous) 
were recorded. These seagrass species were found at 21 and 24 sites, respectively. 
Three groups of macroalgae, green algae, brown algae and red algae, were identified in 
the quadrats. Green algae (e.g., Ulva, Cladophora, Enteromorpha) occurred at 84 sites. 
Red algae were observed at one site and brown algae at six sites. As macroalgae were 
only identified to major taxonomic group, it could not be determined if any 
nonindigenous algal species were present. 
Throughout the West, the vegetation quadrats were dominated by bare area 
(Figure 3.3.7). Relative cover by bare area ranged between 2 and 100% throughout the 
West (Appendix Table 5). Mean relative cover of emergent macrophytes (26%) was 
higher than that of seagrass (9%) or algae (16%) throughout the West (Figure 3.3.7). 
The relative cover of emergent macrophytes ranged between 1 and 100% in the West 
(including all San Francisco sites) (Appendix Table 5). Most emergent macrophyte taxa 
occurred at only a few sites (Appendix Table 4). Eighty-two percent of taxa occurred at 
three or fewer sites. The most frequently occurring emergent macrophyte taxa were 
Jaumea carnosa and Salicornia virginica. The paucity of emergent vegetation at most 
sites may be attributed to the fact that most of the sites in the sample frame were 
classified as unvegetated tide flats (Figure 3.1.2). 
The relative cover by major plant groups (emergent macrophytes, seagrass, 
macroalgae) and bare area displayed geographic patterns (Figure 3.3.7). Bare area 
was highest for sites in Oregon and Washington, while cover by emergent macrophytes 
was highest in California and San Francisco Bay. Mean bare area was 62% in Oregon 
and 63% in Washington. Mean bare area was 42% in California and 42% for sites in 
San Francisco Bay. Mean relative cover of emergent macrophytes was 3% in 
Washington and 7% in Oregon and 38% in California and 62% in San Francisco Bay. 
Cover of emergent macrophytes was higher than that of algae or seagrass in California 
and San Francisco Bay sites. Relative cover of seagrass was higher than that of 
emergent macrophytes in Oregon and Washington sites. Mean relative cover of 
seagrass was less than that of emergent macrophytes or algae in California sites. 
Mean relative cover of algae (all types) was highest for Oregon sites (Figure 3.3.7). 
43 
