Advancing phenology in Europe's last lowland primeval forest: non-linear temperature response

We analysed phenological observations of first flowering and peak flowering dates of 7 species of woodland herbs in the Bialowieia National Park (Poland), Europe's last remaining lowland primeval forest and a World Heritage Site, during 1964-2007. There was substantial evidence for an advance in both first and peak flowering dates and flowering was closely related to temperature, which had risen substantially in this area. Similar advances have been reported from elsewhere, but typically from human-modified habitats. A comparison with contemporary data from the UK suggests that flowering was both later and less responsive in Poland. Examination of the data from the 2 countries over a wide range of temperatures hints at possible non-linear temperature responses; thus estimates of phenological change from linear regression may seriously underestimate changes which may occur in Bialowieia in the future.