Spatial distributions of pollen in surface sediments of the Potomac estuary1

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Abstract
Pollen of trees extracted from surface sediments of the Potomac estuary represent all components of the arboreal vegetation, with the exception of Liriodendron tulipifera (tulip poplar), and reflect the major forest gradients in a broad band adjacent to the estuary. Pollen of common trees restricted to the upper watershed, 60 km upstream of the limit of tidal influence, are not present in downstream estuarine deposits.A comparison of the statistical variability in pollen data from estuarine sediments with tree data in the area adjacent to the estuary suggests that atmospheric or estuarine transport processes erase the local patchiness of the trees from the pollen distributions in the sediment. Although dispersion is selective for different pollen types, none of the pollen is transported far enough to mask regional forest gradients.Pollen distributions in Potomac estuary sediments suggest that once particles of approximate hydraulic equivalence become part of the suspended sediment load, they are not widely dispersed within the estuary before initial deposition.