Lichens on dead wood : A comparison between dead wood in burnt and unburnt areas of Tyresta National Park and nature reserve

Burned forests provide plenty of dead wood that can host rare and threatened species, especially fire dependent species that need charred wood to survive. Few studies have investigated the difference in lichen assemblages on dead wood in forests that have burned with those that have not. In this study lichens on snags of Pinus sylvestris in burnt and unburnt areas of Tyresta national park and nature reserve were investigated, with the aim to assess differences in lichen diversity and richness. In total 42 trees were analysed, and 25 species were identified. No threatened or rare species were found in the burnt area, possibly as none of the snags were charred. There was no significant difference in diversity or richness between burnt and unburnt areas. However, lichens were generally more abundant in the burnt area where the light levels also were higher, especially on the northern sides of the snags. Only macrolichen species were significantly more abundant in the burnt area. The species composition in the areas differed slightly with a majority of microlichen species in the unburnt area while the burnt area had equally many macro- and microlichen species. However, several species of microlichen were missing in the burnt area. Together with previous studies this could indicate that microhabitats forming post-fire are favourable for some lichen but not for others. Further studies are needed to confirm which species are favoured by burning to optimize the restoration and managing of burned forests as well as the conservation of threatened species