Forest fires: How surviving trees can suffer from heat injuries

Forest fires usually leave behind many living but injured trees. These surviving trees are often found to die several years after the fire as a result of legacy effects (post-fire mortality). The underlying physiological mechanisms governing this post-fire tree mortality are not completely understood. To gain better insights into the fire effects on surviving trees, a study in Absam, Tirol, where a large forest fire occurred in 2014, was conducted. We demonstrated that the heat exposure during a fire can lead to permanent impairments of the plant water transport system. Consequently, fire-injured trees are more susceptible to future drought disturbances and thus suffer a higher risk of mortality. As global warming will cause an increase in frequency of forest fires and of drought events, understanding post-fire physiological processes will become highly important to better estimate future impacts of forest fires. 



Fig. 1: Electrical resistivity tomograms of control and fire-exposed Norway spruce (Picea abies) stems.
The water-conducting sapwood of the intact control tree appears as a distinct ring (blue, low electrical resistivity), surrounding the central heartwood (red, high electrical resistivity). The resistivity shifts in the tomography pattern of the fire-exposed stem indicate a profound loss of functional sapwood area, which curtails the water transport from roots to the crown.


Bär A, Nardini A, Mayr S. 2018. Post‐fire effects in xylem hydraulics of Picea abies, Pinus sylvestris and Fagus sylvatica. New Phytologist 217: 1484-1493.


For his paper in the journal New Phytologist DP-student Andreas Bär received the LFUI Best Student Paper Award.

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