Susceptibility of Alpine forest tree species to first- and second-order fire effects

Background

Climate change causes increased risks of wildfires, due to raising temperatures and the increase of drought events. Fires often are not lethal for trees, but rather trigger second-order effects, such as physiological limitations in carbon and water relations or increased susceptibility to pathogens. Knowledge on the susceptibility of European forest species and underlying first- and second order mechanisms is poor, despite fire frequencies and intensities in the Alps, and respective risks for the protective function of mountain forests, increase.

Research questions and hypothesis

This PhD-thesis aims at short- and long-term fire effects on the hydraulics of Alpine forest species. We expect species-specific impairments of the hydraulic safety in several species, which will impair water relations and reduce their resistance against consecutive drought events. We hypothesise fire-induced impairments to be more pronounced in young trees.

Approach and methods

At the main (and additional) study sites, branches and roots of adult trees will be sampled for analyses of hydraulic efficiency (Sperry-Apparatus), safety (Cavitron) and xylem structural measurements (Microscopy, SEM, Syncrotron) before and after heat treatment (temperature test chamber). Similar measurements are planned on young trees. At a natural forest fire site, monitoring (dendrometers, electrical resistivity tomography) of damaged and control trees will be continued and complemented by microbiological analysis on extracted wood cores. On young trees, (combined) effects of fire/heat (including heat plume effects) and drought will be simulated and potential effects on hydraulics analysed (see methods above and porometry, ultrasonic emissions).

Time frame