XVI International Botanical Congess

Changes in phenology (seasonal plant activity driven by environmental factors) from year to year may be a sensitive and easily observable indicator of changes in biosphere. We have analysed phenological data collected by the German Weather Service and found that linear trends in phenological time series are only consistent when covering more than 30 years of observation. The annual growing season of Beech and Birch e.g. in Germany is lengthened by 4 to 5 days in the last 3 decades. Analysing data from more than 30 years of observation in the International Phenological Gardens in Europe, we found that spring events, such as leaf unfolding, have advanced by 6 days, whereas autumn events, such as leaf fall, have been delayed by 4.8 days. This means that the average annual growing season has lengthened by 10.8 days since the early 1960s. These shifts can be attributed to changes in air temperature.