Landscape openness and pollen records: a simulation approach

A model of pollen deposition on the surface of an entire basin is developed to estimate pollen source area, and results are compared with those for a point at the center of a basin (I. C. Prentice, 1985, Quaternary Research 23, 76-86; 1988, "Vegetation History," (pp. 17-42, Kluwer Academic). This model is more appropriate for approximating the source area of pollen in lake sediment, since mixing in lake water and focusing of sediment redistribute pollen originally deposited over the entire surface. In general, the pollen source radius for the entire basin surface is 10-30% smaller than the source radius for a point at the center; the difference in the source radius is more profound for heavier pollen types such as spruce and sugar maple than for lighter types such as oak and ragweed. The average pollen input to the entire surface is more strongly influenced by nearby pollen sources than pollen deposition at the center. The pollen record from a lake may therefore provide different spatial resolution than the record from a bog of similar radius.