Distribution of seed plants with respect to tide levels and water salinity in the natural tidal marshes of the northern San Francisco Bay Estuary, California

摘要: Shoaling of subtidal and intertidal mud flats has permitted tidal marshes to spread across large marginal areas the San Francisco Bay estuary during past several thousand years. By 1850 A.D. estuary, including those Sacramento Joaquin Delta, covered an area nearly twice as open water. Nearly 95 percent these have been diked or filled 125 Species distributions along leveled transects at six indicate that elevation water salinity are principal ecological factors control distribution seed plants in remaining natural northern estuary. Marsh surfaces situated near mean tide level populated by robust monocotyledons (e.g., Spartina foliosa, Scirpus californicus), whereas high-tide levels support dicotyledons a few small monocotyledonous species Salicornia virginica, Distichlis spicata). Marshes seaward end typically occupied 10-15 salt-tolerant (e^g., foliosa virginica), riverward inhabited many 30 species, most which known tolerate moderate amounts salt spp., Phragmites communis, Typha latifolia). INTRODUCTION Purpose More than half California (MacDonald Barbour, 1974, p. 212-213). Despite widespread concern for preservation wetlands, published information about their flora is scanty. Quantitative data on gathered only southern arm (Hinde, 1954; Rountree, 1973, 203-225). Published fringing part restricted general descriptions lower reaches (Howell, 1970; Ffclice, 1954), topical studies located upper estuary.and subjected seasonal inundation duck clubs (George, Anderson, McKinnie, 1965; Mall, 1969; Rollins, 1973). The purpose this study make reconnaissance ~of This applications: (1) regional marsh appears be controlled salinity. Our records present plant permit comparative some future date, when salinities may differ because proposed reductions volume fresh-water inflow (California Dept. Water Resources, 1960). (2) within each mainly surface they grow. Knowledge ranges permits detection historic uplift subsidence from changes Gilbert, 1908, 81-87; Jepson, 1908; Harvey, 1966, 22). (3) living can used interpret former sea fossils contained core samples deposits. These interpretations determination shoreline vertical crustal movement recent geologic Redfield, 1972; Atwater, Hedel, Helley, unpub. data). Acknowledgements supported U.S. Geological Survey's efforts identify earthquake hazards region. We grateful private .land-owners Department Parks Recreation granting access land. Steve Talco drafted plates 3-8, Virgil Frizzell reviewed manuscript. METHODS OF STUDY angiosperms were investigated noting marshes. chosen range location (fig. I) order determine effect floral populations. None pristine all undergone years attributed activities man. As much possible, however, we visited changed very little according following criteria (table 1): minimal disruption circulation levees ditches, particularly landward edge marsh; existence least * prior 1850; minimal' land due withdrawal ground gas. In addition, tried investigate displayed transitions high-marsh low-marsh low^narsh barren mudflats. poorly represented Petaluma, Fairfield, Bethel Island, where drop abruptly into man-made sloughs 1; 5, 7, 8). A topographic profile was constructed spot elevations horizontal intervals m less (plates 3-8). Elevations referenced nearest bench mark National Geodetic Survey (formerly, Coast Survey). leveling monuments, obtained early 1950*s late 1960*s, minimize errors (see explanatory notes bench-mark transferred Figure 1. fresh 25 California, Sierra Nevada (snow-capped top), meets Pacific Ocean. report, refers open-water tidal-marsh between Golden Gate eastern Sacramento-^San Joatjuin thereby Pablo Bay, Carquinez Strait, Suisun Sacramento-San Delta index map). Triangles map show approximate locations marches studied Infrared photograph courtesy Aeronautics Space Administration (Ames Research Center, Moffett Field, Calif.), taken April 14, 1972, altitude 2(X,000 m(65,000 ft) U-2 aircraft.