Quantitative representation of local forest composition in forest‐floor pollen assemblages

1 We compared modern pollen assemblages from 60 moss polster sites in northern New York with forest composition data within 20–120 m of the sites using extended R ‐value (ERV) models, which correct for non‐linearities arising from use of pollen percentage data. Our sites were concentrated in two regions, one dominated by Tsuga and hardwood ( Acer , Betula , Fagus ) forests, and the other by Tsuga , Pinus , Betula , Acer and Quercus forests. 2 Our results confirm that forest‐floor pollen assemblages are dominated by pollen originating from trees growing more than 20 m from the site of deposition. However, our results suggest that background pollen percentages were overestimated by Jackson & Wong in 1994, owing to unusually high Pinus pollen production in the year of their sampling. 3 Expansion of our vegetation sampling radius from 20 to 120 m resulted in modest but consistent improvement in model fit and a decrease in background pollen percentages. 4 ERV model parameters (slope and background) differed substantially between the two study regions, primarily owing to differences in background pollen productivity and dispersal from regional sources. 5 High background pollen percentages may lead to poor estimation of calibration parameters in regions of complex vegetation patterns. Expansion of the vegetation sampling radius to reduce the background component may lead to better parameter estimates. 6 Calibration of pollen–vegetation relationships requires definition of the vegetation term so that it approximates the vegetation sampled by the pollen assemblages. Critical challenges are to define better the appropriate vegetation sampling area and distance‐weighting functions for application to pollen–vegetation calibration.