| Summary: | The number of forest dwelling woodland caribou (Ranger tarandus caribou) in Ontario is declining. One of the reasons believed to be causing this decline is a reduction in critical habitat due to harvesting and post-harvest management practices. Critical habitat for woodland caribou includes a large amount of lichen biomass, which is their primary winter forage. In this study, the environmental variables that are most important for explaining lichen diversity are determined and the influence that silvicultural practices have on these variables is assessed. A method for estimating lichen biomass at the stand level was developed so comparisons could be made between forest stands and different silvicultural practices. This method requires the identification of individual lichen species. Therefore, a key and species descriptions are provided for all the fruticose lichen species in Ontario, which is the form of all the species that occurred with a high biomass in the stands assessed. Using these tools and the method developed for estimating lichen biomass, the lichen richness and biomass in forest stands across northern Ontario were examined and compared. The variables that were most important for explaining lichen richness were the number of microhabitats, the variation in the amount of light coming through the canopy and the stand age. For lichen biomass, the most important explanatory variables were the total amount of light coming through the canopy, stand age and sandy soil. Silvicultural treatments were found to have an effect on lichen diversity in the short-term (1 yr) and the long term (25-40 yrs). Lichens exhibited different tolerances to herbicides ranging from no effect to 100% mortality one year post-treatment. The long-term effects of herbicides and planting were found to alter lichen communities. Stands with herbicide treatments also had less lichen biomass than the rest of the stands examined. The creation or conservation of mature forest stands on sandy soil with low canopy closure and high structural ...
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