Figure 7.3. Percent abundance and concentration (pollen/gram dry sediment) of pollen of Ambrosia, Poaceae, and Plantago in core MD99-2209. Arrows indicate times of initial land clearance for farming, maximum land clearance and changing agricultural practices, and urbanization, based on abundance patterns of these weedy species.

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U.S. Department of Interior, U.S. Geological Survey
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