Size distinctions between Betula pollen types - A review

It is difficult to reliably distinguish Betula species solely on pollen morphological criteria. Size differences between the pollen of different Betula species have proved to provide a basis for their separation. Pollen grain size is affected by both sedimentary environment and laboratory treatment. Only gains from similar sediment lithologies that have had identical laboratory treatment can be considered comparable in size with each other. A simple size comparison between modern and fossil pollen is not advisable. In this paper previous methods for the separation of birch pollen types are reviewed and some new measurements of the Finnish birch species are presented and discussed.