Timing of plant phenophases in Finnish Lapland in 1997-2006

We investigated whether there were consistent changes in plant phenophases in 1997-2006 at 13 observation sites in Finnish Lapland, and whether such changes could be explained by measured climatic conditions. The phenological data were collected within the Finnish National Phenological Network organised by the Finnish Forest Research Institute (Metla). During the observation period, the effective temperature sum (ETS) increased on average by 17.7 day degrees/year, while the maximum snow depth decreased by 3.5 cm/year and the timing of snow melt advanced by 1.4 days/year. The spring phenophases advanced on average by 1-2 days/year in the case of most of the species studied, which resulted in a lengthening of their growth period. The autumn phenophases did not show any trends or relationships with respect to the studied climatic conditions, however. The mean May temperature and the date of snow melt explained best of all the onset of spring in the studied species.