Assessment of the minimum sample size required to characterize site-scale airborne pollen

Abstract

Many palynological investigations require the comparison of large collections of samples and here the optimization of the effort is crucial. A method to determine the pollen sum according to the intrinsic characteristics of the site pollen composition is proposed. Different variables such as pollen spectra, typological lists, richness, diversity, intra- and inter-sites affinities, are alternatively analyzed in order to determine the minimum sample size and the results are compared. An example of this methodology is developed for the airborne pollen from an agroecosystem in the Pampean grasslands. Increasing pollen counts from 150 to above 2700 does not yield different results among the dominant and subdominant types, which account for 70%-80% of the pollen sum. Both diversity estimates and similarity among sites are not significantly affected when quantitative coefficients are employed. As pollen counts increase, there is an increment in the number of types, but the types added with counts over 150 are always rare, their overall relative frequency never exceeding 6%. The minimum sample size obtained as shown here provides the necessary information to reconstruct the major pollen fraction of the site and it provides reliable estimates of the typologie diversity and the affinities among sites. © 1998 Taylor & Francis Group, LLC.