Potential biodiversity impacts of forest biofuel harvest: lichen assemblages on stumps and slash of Scots pine

Harvesting stumps and logging residues for energy production may have negative impacts on forest species, especially those associated with dead wood. We assessed the potential impact of biofuel harvest on epiphytic lichens by studying the lichen assemblages on stumps and downed fine woody debris (FWD) of Scots pine (Pinus sylvestris L.) in clear-cut, mature managed, and old-growth forest stands in eastern Finland. We also examined the impact of tree retention level and prescribed burning on these assemblages. A total of 102 lichen species (including 13 red-listed species) were observed, with 95 species on stumps and 69 species on downed FWD. Composition of the species assemblages differed between stumps and downed FWD and between stumps of different age. Tree retention (in comparison with clear-cut sites) and prescribed burning resulted in a slightly higher species richness on cut stumps 12 years after harvest but did not affect the assemblages on downed FWD or older stumps. We conclude that stumps and downed FWD of Scots pine can host high numbers of lichen species, including red-listed ones. Most of the species occurred also on other substrates and are, therefore, not likely to be affected by biofuel harvest. However, for dead wood dependent lichen species, intensive biofuel harvest is potentially harmful, though the severity of this impact likely depends on the landscape-level availability of other woody substrates.