Climate change makes apple trees bloom earlier

Researchers are studying the effects of global warming on vegetation

Apple trees are always blooming © IfL
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In many regions of Germany, the apple blossom starts earlier and earlier. This is illustrated by current maps of the Leibniz Institute for Regional Geography (IfL), which have now been published in the online journal National Atlas.

Long-term records of periodic phenomena in plants have shown that flowering and leaf development are continuing to move forward in Europe. After all, the change in the last 30 to 50 years was 1.4 to 3.1 days per decade, the researchers said.

The reason is the general warming. Apple trees start to bloom 2.5 to 6.7 days earlier when the air temperature rises by one degree Celsius.

Connection with temperature curve occupied

Time series of the beginning of flowering, for example for Jork in the Old Country near Hamburg, for Göttingen or also for Endingen in the Kaiserstuhl show a clear connection with the continuously rising temperature curve.

However, the current Germany maps of the IfL on apple blossoms also illustrate that this general trend is significantly less pronounced in climatically favored areas. Reason: Here, the amount of radiation required for growth is reached early in the year even in normal years. display

According to the scientists, a strong shift of the so-called phenological phases was observed in 2007, when the apple bloom averaged two to three weeks rather than the long-term average.

"Fingerprint" of climate change on the trail

Such outliers, however, are no indication of climate change, meteorological extreme events have also been in the past again and again. According to various sources, for example, the winter of 1795/96 was so mild that fruit trees in the eastern Harz foreland already flourished in January.

Altogether, the current IfL article makes it clear that phenological data, according to the interpretation of the Göttingen geographers Jobst Augustin and Stefan Erasmi, are not only an indicator of the regional climate, they can also be interpreted as a kind of "fingerprint" of climate change.

(idw - Leibniz Institute for Regional Geography, 23.05.2008 - DLO)