Snag degradation pathways of four North American boreal tree species

Most species survival curves exhibited a reverse sigmoid function. Trembling aspen, jack pine and to a lesser extent balsam fir presented significant lag times before initiation of a period with high fall rates. Black spruce experienced more snag losses during the first years following death. Jack pine was clearly the most persistent species due to snags high resistance to fall and stem breakage. Within the range of tree diameters in our study area, diameter per se did not significantly influence fall probability. Differential degradation pathways of the four species translate individualistic responses that are related to species autecology. This has important implications for all ecological functions related to deadwood and should be considered when planning retention strategies of legacy trees in an ecosystem management perspective.