Assessing the restoration and the dispersal of reindeer lichen after forest fire in northern Sweden: Results after eleven growing seasons

In circumboreal regions, Rangifer populations depend heavily on ground reindeer lichens (Cladonia subgenus Cladina) during the winter, but this critical resource was depleted over the 20th century as a result of land encroachment and habitat loss. Fires, both wild and controlled, can also contribute to the decline of reindeer lichen. Depending on the context, accelerating the return of winter pasture through reindeer lichen transplantation after fire may be needed to conserve threatened caribou populations and semi-domestic reindeer herding. Following a field experiment established in 2008, two years after a forest fire, we evaluated the success of restoration through lichen transplantation, measuring biomass on restoration, control and reference sites. We also assessed the dispersal of lichen fragments from the restoration plots into the surrounding burnt area. Eleven growing seasons after lichen transplantation, the lichen biomass measured on restoration sites (62 g m⁻²) was on average significantly higher than on control sites (0.8 g m⁻²), but remained non-significantly lower than on reference sites (109 g m⁻²). This confirms the success of the transplanting operation and the remaining progress towards a fully restored lichen mat. The distance distribution of lichen fragments showed that reindeer lichen had dispersed by at least 20 m from the restoration plots, and locally by much greater distances, of up to 60 m. The absence of a clear pattern of dispersal on all sites indicates the importance of microsite conditions and post-dispersal processes. Perspectives for future restoration operations are discussed, including the fire-lichen-Rangifer relationship, and implications for local and Indigenous populations who depend on them.