Changing elevation,accretion, and tidal marsh plant assemblages in a South San Francisco Bay tidal marsh |
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Authors: | Email author" target="_blank">Elizabeth?Burke?WatsonEmail author |
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Institution: | (1) Geography Department, University of California, 507 McCone Hall, Berkeley, CA 94720, USA;(2) Department of Land, Air & Water Resources, University of California, Davis, 228 Veihmeyer Hall, One Shields Ave., Davis, CA 95616, USA |
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Abstract: | Analyses of organic content, pollen, and the carbon-isotopic composition of a 3.5-m sediment core collected from a subsided
tidal marsh located in South San Francisco Bay, California, have provided a 500-yr record of sediment accretion and vegetation
change before, during, and after a rapid 1 m increase in sea level. Core chronology was established using14C dating of fossil plant material, the first appearance of pollen types produced by plants not native to California, and changes
in lead concentrations coincident with anthropogenic contamination. Prior to the mid 19th century, rates of sediment accretion
were between 1 and 4 mm yr−1; sediment accretion accelerated to an average of 22 mm yr−1 following the initiation of subsidence. Changes in tidal marsh vegetation also accompanied this depositional change. Vegetation
shifted from a high to low marsh assemblage, as indicated by a larger percentage of grass pollen, rhizomes ofSpartina foliosa, and a strong C4 signal. Between 1980 and 2001, Triangle marsh again developed high marsh vegetation, as indicated by higher percentages of
the Amaranthaceane pollen type, seed deposition, includingSalicornia spp., and more negative carbon isotopic ratios. |
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