geographic patterns in transect vegetation cover of major plant groups can be attributed 
to differences in habitat types among states. Marsh habitat was more common in 
California and San Francisco Bay, while tidal flat habitat was more abundant in 
Washington and Oregon. 
Taxa occurrence and mean relative cover of common vegetation taxa in the 
transects also displayed geographic patterns. The largest numbers of emergent 
macrophyte species were observed in the transects of sites in California (n = 11) and 
San Francisco Bay (n = 18), although most of these species occurred at fewer than 3 
sites. Nine emergent macrophyte species were observed in the transects of Oregon 
sites. The transects of only four sites in Washington had emergent macrophyte cover 
and only two species, Juncus gerardii and S. alterniflora, were present in Washington. 
Because most taxa only occurred at a few sites, average percent cover of taxa was 
calculated as the average cover at sites where the taxa occurred and not across all 
sites. Mean cover of S. virginica was 48% in California sites and 76% in San Francisco 
Bay sites (Figure 3.3.16). This species occurred at one site in Oregon and was not 
found in Washington. Mean cover of J. carnosa was 39% in California sites. This 
species was present at one site in San Francisco Bay and was present in neither 
Oregon nor Washington sites. Of the three remaining species occurring at more than 
five sites, B. maritima and S. foliosa were only encountered in California and San 
Francisco Bay sites. Distichlis spicata was not observed in Washington. Again similar 
to vegetation quadrats, geographic patterns in occurrence of common emergent 
macrophyte taxa may be attributed to differences in habitat types among states 
Seagrass species were observed in the quadrats of California, Oregon and 
Washington sites. Zostera marina was present in the vegetation transects of all three 
states. Mean relative cover of Z. marina was similar for Washington and Oregon sites 
(Figure 3.3.17). For Washington sites, mean relative cover of the invasive seagrass, Z. 
japonica, was higher than that of Z. marina, 52% and 28%, respectively. Zostera 
japonica did not occur in California or San Francisco Bay (Figure 3.3.18). Mean relative 
cover of green macroalgae was highest at California sites (63%; Figure 3.3.19). Green 
macroalgae did not occur in San Francisco Bay. 
Nonindigenous emergent macrophytes and seagrass were encountered in the 
transects at 33 sites throughout the study area. Spartina alterniflora was observed at 
three sites in Washington and Z. japonica was observed at sites in both Oregon and 
Washington. Lepidium latifolium was found at one site in San Francisco Bay. Mean 
relative cover of nonindigenous species was low (14%) throughout the West (Figure 
3.3.20). Mean cover by nonindigenous species was highest in Washington (37%), with 
nonindigenous species being found at 21 sites. Sites in Washington had both S. 
alterniflora and Z. japonica. No nonindigenous species were observed at California 
sites. 
47 
