Can partial-cut harvesting be used to extend the availability of terrestrial forage lichens in late-seral pine-lichen woodlands? Evidence from the Lewes Marsh (southern Yukon) silvicultural systems trial.

Abstract

In northern British Columbia and southern Yukon woodland caribou forage extensively on terrestrial lichens, predominately mat-forming Cladina species in late-successional pine-lichen woodlands. Many of these stands are now reaching a point in their development where lichen abundance declines as feather-moss mats increase. We evaluated the response of forest floor plant communities in pine-lichen woodlands from the southern Yukon Lewes Marsh partial-cutting trial eight years after harvesting. Photoplot results documented a major decline (>60% ± 5.6% S.E.) in the mean surface area of existing large clumps of C. mitis in control (unharvested) treatments, whereas mean surface area of large C. mitis clumps declined by 28% (± 15% S.E.) in the one-third basal-area removal, and showed an increase of 13.5% (± 25% S.E.) in the two-third’s basal-area removal. Line-intercept transects documented no changes in overall stand-level lichen abundance between pre- (2012) and post-harvest (2021) measurements, while feather-moss mats and dwarf shrubs showed declines and increases respectively in partial-cutting harvest plots. Stand thinning may provide a bridging strategy to extend the period of forage lichen availability in late-seral pine-lichen woodlands, an important consideration in landscapes where increasing severity and frequency of fires is changing the seral-state distribution of caribou habitat.