Wednesday, 19 November 2003: 8:30 AM
The Effect of Fire Severity on Early Development of Understory vegetation Following a Stand Replacing Wildfire
Four boreal mixedwood stands burned by the 1999 Black River wildfire in southeastern Manitoba were sampled to study the effect of fire severity on the early (1999 to 2003) dynamics of vegetation recovery. Three fire severity classes (scorched, lightly burned, and severely burned) were identified on each stand based on the degree of forest floor consumption. Six plots per severity class were randomly selected on each stand. It was found that fire severity significantly affected post-fire vegetation response, and changes in plant community over time were depended on fire severity. Among the three major life form groups, abundance of woody plants reduced with fire severity while abundance of moss and liverwort increased with fire severity. Abundance of forbs and grass was higher on the intermediate fire severity. As expected, invasive species increase with fire severity while sprouting species decreased with fire severity. Seedbank species performed the best at the intermediate fire severity. Species richness and diversity were reduced only in the 1st post-fire year by severe burning. The rate of plant community recovery, in reference to mature stands, was decreased with fire severity. Nevertheless, most species found in mature stands were currently present on each fire severity class. Unique species, especially those unique to slightly and/or severely burned plots, were not found in mature stands. Within the four post-fire years, rapid changes were observed only during the initial three post-fire years regardless of fire severity. As most differences observed among the three fire severity classes remained significant at the 4th post-fire year, how long it would take for plant communities developed on these fire severity classes to converge is not clear.