Page 48 - Green knowledge 2023

Photo: John Yngvar Larsson
Warmer climate yields more heat-loving trees
What do trees do when the climate changes, and the weather gets warmer? The trees’ temperature requirements provide us with the answer.
Trees are at the mercy of the local conditions they grow in. They need sun and warmth to germinate and thrive, and summer temperatures affect how far north and how high up the mountains they can grow. However, some types of trees, such as dwarf birch, are not so picky about temperature. As long as the mean temperature of June, July, August, and September is above 4.3 degrees, dwarf birch will grow.
The dwarf birch has the lowest summer temperature requirement of all Norwegian tree species. More heat-loving tree species like elm, ash, beech, oak, hazel, lime, maple, and black alder demand higher summer temperatures. Precisely this high tempera- ture requirement is the reason why species like ash, oak, and beech are only found in certain areas in the southern part of Norway.
But what happens if the average summer tempera- tures increase?
Increased temperatures over the past century have allowed different tree species to grow further into the country and higher up in the mountains than before.
Therefore, when forest owners plan for the future, knowledge is needed about how temperature changes affect the growth and development of trees. The tree species we choose to plant today – whether it is spruce, pine, birch, black alder, or beech – will have to grow and thrive in an entirely different climate than today.
Climate researchers at NVE and NIBIO have thus produced maps showing changes in mean summer temperatures over the last 60 years. Changes in mean temperature of the four summer months are relevant for forestry, in that heat-loving trees like beech, for example, might extend further into the country – if other important requirements are also met.
Purpose:
Collaboration: Funding:
Contact:
Develop maps illustrating changes in temperature during the growing season as a basis for selecting future tree species.
The Norwegian Water Resources and Energy Directorate (NVE) The Research Council of Norway
Research Scientist Stephanie Eisner. Email: stephanie.eisner@nibio.no,
phone: (+47) 904 13 678. Division of Forest and Forest ResourcesØverst i skjemaet
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