Acknowledgements
This investigation was financed by the State Forest Authorities of Mecklenburg-Vorpommern. The author thanks Martin Theuerkauf, Institute of Botany and Landscape Ecology, Ernst-Moritz-Arndt-University Greifswald, Germany, for providing the pollen counts of the three lowest samples and Pim de Klerk, State Museum of Natural History, Karlsruhe, Germany, for commenting on the manuscript and improving the English.
Disclosure statement
No potential conflict of interest was reported by the author.