1. Norwegian Forest and Landscape Institute; NO-1431 Ås Norway
2. Laboratory of Palaeoecology and Archaeobotany; Department of Plant Ecology; University of Gdańsk; PL-80-308 Gdańsk Poland
3. Institute of Plant Sciences and Oeschger Centre for Climate Change Research; University of Bern; CH-3013 Bern Switzerland
4. National Centre for Biosystematics; Natural History Museum; University of Oslo; Blindern NO-0318 Oslo Norway
5. Swiss Federal Research Institute for Forest; Snow and Landscape Research (WSL); CH-8903 Birmensdorf Switzerland