Restoration of reindeer lichen pastures after forest fire in northern Sweden: Seven years of results

Abstract

Fire suppression since the 19th century has modified the functioning of boreal forest ecosystems in northern Sweden. In the long run, it induces changes in understory vegetation that result, especially on mesic sites, in feather mosses and Ericaceous dwarf shrubs outcompeting ground lichens, thus decreasing winter pastures for reindeer husbandry. In 2008, a field experiment was established in which, two years after a large forest fire, reindeer lichen (Cladonia spp.) was transplanted across various plots. The general objective was to accelerate the recovery of lichen-rich reindeer pastures, and test the ability of lichen thalli to establish on burnt surfaces following different post-fire treatments (tree harvest and standing trees retained), in different transplantation seasons (summer and winter) and at different doses (0.45Lm−2 and 2.25Lm−2). The abundance and level of occupancy of viable and established lichen fragments was determined in 0.25m2 quadrats in 2010, 2013 and 2015. There was a continuous increase in lichen establishment over time, and seven years after transplantation, established lichen occupied, on average, 55% and 83% of the 0.25m2 quadrats treated with the lower and higher doses, respectively. Nine years after fire, no lichen had colonized the control, i.e. the burnt surface outside the experimental area. At the site with standing trees retained, lichen had already formed a well-established mat with a significantly higher lichen occupancy and abundance than in the open, clear-cut sites, where lichen agglomerated in proto-mats. Lichen transplanted in late-summer exhibited higher abundance and occupancy than that transplanted in late-winter. On average, the difference in lichen occupancy and abundance between different doses after seven years was of lower magnitude than between the doses of lichen transplanted initially. The experiment reveals useful results for the restoration of reindeer pastures and for specifying fire management regimes adapted to both forestry and reindeer husbandry.