Tidal Wetland Vegetation in the San Francisco Bay-Delta Estuary

Abstract

We analyzed tidal wetland vegetation patterns in the San Francisco Bay-Delta estuary (Bay-Delta) and discuss their significance for future conservation. Our objective was to conduct a balanced, random sample of six historic "remnant" tidal wetlands along a salinity gradient that ranged from southern San Pablo Bay to the lower Delta. We also wanted to compare diversity among these sites at five different scales, ranging from small subplots to total species per site. We randomly established twenty 0.1-ha plots at each site, and sampled ten 7-m 2 circular subplots (subplot scale) in each plot for species presence and cover. We calculated total species per plot (plot scale) and total species per site (site scale) based on these subplot data. We calculated importance values for each species found in subplots based on frequency of occurrence and proportion of total cover at each site. In addition, we recorded species found within the 0.1-ha plot but not sampled in subplots (plot_all scale), and calculated the total species for each site based on these plot_all data (site_all scale). Thus, richness at each site was evaluated at five different scales that ranged from 7 m 2 to 20,000 m 2 . We conducted a one-way ANOVA that compared mean richness among three scales with continuous data: subplot, plot, and plot_all. At lower estuary (San Pablo Bay) sites, richness values at these three scales were significantly lower than upper estuary (Suisun-Delta) sites. In Suisun-Delta sites, significant differences in richness varied, depending on sampling scale. Rush Ranch, a brackish wetland, had the highest average number of species per plot, whereas Sand Mound Slough, a freshwater wetland, had the highest average number of species at the subplot scale and the most total species at the site_all scale. Sand Mound Slough also had the highest number of unique species (22) compared to the other sites. We found a strong negative correlation (r 2 = 0.99) between total species number and salinity (the most in the Delta at the lowest salinity, and the least at China Camp with the greatest salinity). Our analysis suggests the following conservation recommendations: (1) restore habitat for freshwater plant species diversity in the Delta; (2) restore transitional brackish wetland habitat in salt marshes of the San Pablo Bay and San Francisco Bay; and (3) focus on control of pepperweed (Lepidium latifolium) in brackish marshes.

Can community structure track sea‐level rise? Stress and competitive controls in tidal wetlands

“…Although the difference in salinity is small, the effect on species diversity (Vasey et al. ) and biomass (Vasey, Parker, Herbert, & Schile unpublished data) is notable.…”

Coupled impacts of sea-level rise and tidal marsh restoration on endangered California clapper rail

“…Field surveys indicate that tidal marshes with a higher ambient salinity level tend to have a higher density of clapper rail (Fig. S11) because of vegetation changes associated with this higher salinity (Evens and Collins, 1992;Parker et al, 2011;Vasey et al, 2012). The SLR-induced salinity rise results in more marshes with salinity level in the preferable range (22.1-30.0 psu).…”

“…Salinity and tidal conditions represent two primary physiological stressors of coastal wetland vegetation and thus have the potential to drive changes in wetland ecosystem composition and productivity (Parker et al, 2011;Vasey et al, 2012;Woodrey et al, 2012).…”

Field assessment of environmental factors constraining the development and expansion of Schoenoplectus californicus marsh at a California tidal freshwater restoration site

“…Schoenoplectus californicus is an important plant species in many of the freshwater marshes of the San Francisco Bay Estuary (Watson and Byrne 2009;Vasey et al 2012). It is native to California and occurs in marshes around the globe (de Lange et al 1998;Banack et al 2004;Pratolongo et al 2008).…”