Moving beyond the cambium necrosis hypothesis of post-fire tree mortality: cavitation and deformation of xylem in forest fires

Abstract

It is widely assumed that post-fire tree mortality results from necrosis of phloem and vascular cambium in stems, despite strong evidence that reduced xylem conductivity also plays an important role. In this study, experiments with Populus balsamifera were used to demonstrate two mechanisms by which heat reduces the hydraulic conductivity of xylem: air seed cavitation and conduit wall deformation. Heat effects on air seed cavitation were quantified using air injection experiments that isolate potential temperature-dependent changes in sap surface tension and pit membrane pore diameters. Heat effects on conduit wall structure were demonstrated using air conductivity measurements and light microscopy.

Citation

Michaletz, S.T.; Johnson, E.A.; Tyree, M.T. 2012. Moving beyond the cambium necrosis hypothesis of post-fire tree mortality: cavitation and deformation of xylem in forest fires. New Phytologist. 194: 254-263.