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Combating the Drought

Why forests in Canada are unable to withstand the increasing lack of water

Freiburg, Dec 20, 2018

Combating the Drought

A section through a pine needle shows two pores visible on the surface. These “stomata” regulate evaporation and CO2 absorption. Illustration: Miriam Isaac-Renton

An international team from Canada, Germany and Switzerland, including Prof. Dr. Heinrich Spiecker of the Chair of Forest Growth at the University of Freiburg, has shown why trees’ tolerance to dryness is low in the boreal north-west of Canada, using information stored in the annual growth rings of pines. The researchers have published their results in the science journal “Nature Communications”.

The scientists found that a lack of water damaged the cells of the pine trees from this region. They only have thin cell walls, and in droughts this can lead to air embolisms: this is when air penetrates the tree and disrupts the flow of water inside. The scientists also showed that when it is dry, the trees do not close their stomata. These are pores that act like tiny valves to control water loss in the pine needles. So the forests in this region are incapable of withstanding the occurrence of drought, which is expected to increase in the future.

The team’s results also indicate a potential solution to the problem: pine trees from southern latitudes are more resistant to drought. This means that the tolerance of the forests can be increased if they are planted slightly further north.

Original publication:
Miriam Isaac-Renton, David Montwé, Andreas Hamann, Heinrich Spiecker, Paolo Cherubini, Kerstin Treydte: Northern forest tree populations are physiologically maladapted to drought, Nature Communications, 9:5254.


Prof. Dr. Heinrich Spiecker
Professor of Forest Growth
University of Freiburg
Tel.: +49 761 203-3736