Lichen it: Optimizing post-fire caribou lichen transplantation and assessment

Caribou lichen species are common in mid- to late-seral boreal forests, serving as an important winter diet staple for boreal woodland caribou. However, as climate change causes boreal wildfires to increase in size, severity, and frequency, available tracts of mature forest are decreasing, diminishing the extent of mature caribou lichen stands. Caribou lichens reproduce vegetatively, so bigger and more severe fires could exacerbate their dispersal limitations, potentially extending the timeline for caribou lichen stand recovery beyond 80 years. Trials have shown that “transplanting” caribou lichen fragments into disturbed areas can lead to the establishment of caribou lichen mats; as such, caribou lichen transplantation (CLT) could accelerate the recovery of caribou lichen stands by compensating for their dispersal limitations. However, much remains ambiguous about the ideal transplantation locations in burned forests, as well as the best way to assess whether CLT has been successful. In my thesis, I evaluated the health and retention of caribou lichen fragments two years post-transplantation at 50 burned plots in the Dehcho region of Northwest Territories, Canada. My thesis had three objectives: 1) to identify the macro- and microenvironmental factors influencing CLT success, including the stand and fire history, the abiotic environment, resource competition, and interspecies associations; 2) to determine if three commonly used CLT success measures (fragment retention, chlorophyll fluorescence, and vigour) respond similarly to environmental conditions, and 3) to develop an accessible dichotomous key that resource management practitioners can use to identify optimal CLT locations in burns. My results showed that CLT is more successful in sunny, dry, and conifer-dominated burns and in burned peat bogs. They also point to vegetative species that were indicative of CLT success, such as Vaccinium vitis-ideae and Rhododendron groenlandicum. My results also showed that fragment retention, chlorophyll fluorescence, and vigour – three common measures of CLT success – were not strongly correlated, indicating that these methods capture different aspects of success and should not be used interchangeably. My results will help CLT practitioners identify optimal CLT locations in burns and to assess the outcomes effectively, improving CLT efficiency and offering new possibilities for boreal woodland caribou conservation efforts.

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