"Even under warmer conditions, we won't be seeing 'green Christmases' under freshly blooming trees," says Prof. Annette Menzel, TUM Chair for Ecoclimatology and a fellow of the TUM Institute for Advanced Study. "Nonetheless, the differing growth patterns will affect the entire plant and animal world. The native tree species in our forests have only a limited ability to adapt themselves to climate change."
Shortened winter in the climate chamber
For their experiments, the researchers used twigs around 30 centimeters long from 36 different trees and shrubs, which they exposed to different temperature and light conditions in climate chambers. Each climate chamber experiment lasted six weeks. The twigs came from the "Weltwald" or "World Forest" near Freising, in which Bavarian state foresters have planted stands of trees from different climate regions.
The cold effect showed most strongly with the beeches, the hornbeams, and the North American sugar maple. With shortened cold periods, bud burst occurred significantly later. In contrast, the lilac, the hazel bush, and the birch proved to be less dependent on the cold.
"Overall, however, a chaotic picture emerges," Menzel adds. "Through warmer winters, the usual sequence of leaf development can get completely mixed up. Many of the cultivated species that are at home today in central Europe come originally from warmer climate zones. In the absence of adequate protection against freezing, they could become victims of their own too-flexible adaptation and freeze to death in a late frost in the spring."
|Contact: Barbara Wankerl|
Technische Universitaet Muenchen