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Linköping University | Department of Physics, Chemistry and Biology Master thesis, 60 hp | Biology programme: Physics, Chemistry and Biology Fall term 2020 and spring term 2021 | LITH-IFM-x-EX--21/3965--SE How do saproxylic beetles differ in spruce (Picea abies) forests of different age? A comparison between nature reserves and production forests, in county of Östergötland. Rebecca Petersen Examinor, György Barabas, IFM Biology, Linköpings universitet Supervisor, Nicklas Jansson, IFM Biology, Linköpings universitet Table of contents 1 Abstract .......................................................................................................................................... 3 2 Introduction .................................................................................................................................... 3 3 Material and methods ..................................................................................................................... 5 3.1 Study sites ............................................................................................................................. 5 3.2 Sampling design .................................................................................................................... 6 3.3 Sorting species ...................................................................................................................... 8 3.4 Ecological variables .............................................................................................................. 8 3.4.1 Basal area ......................................................................................................................... 8 3.4.2 Dead wood ....................................................................................................................... 9 3.4.3 Vegetation cover ............................................................................................................ 10 3.4.4 Canopy openness ............................................................................................................ 10 3.5 Statistical analyses .............................................................................................................. 11 4 Results .......................................................................................................................................... 11 4.1 Differences between sites .................................................................................................... 11 4.1.1 Sampling results ............................................................................................................. 11 4.1.2 Species composition ....................................................................................................... 14 4.2 Ecological variables ............................................................................................................ 15 4.2.1 Correlations .................................................................................................................... 15 4.2.2 Impact ............................................................................................................................. 15 5 Discussion .................................................................................................................................... 17 5.1 Differences between sites .................................................................................................... 17 5.2 Ecological variables ............................................................................................................ 18 5.3 Improvements of management ............................................................................................ 19 5.4 Conclusions ......................................................................................................................... 19 5.5 Societal & ethical considerations ........................................................................................ 19 6 Acknowledgment .......................................................................................................................... 20 7 References .................................................................................................................................... 21 8 Appendix ...................................................................................................................................... 25 2 1 Abstract Today, old growth forests are continuously decreasing, due to deforestation, threatening species to extinction. Species dependent on dead wood, different stages of decaying wood, large trees, and forest cover continuity have a particularly high risk of extinction, such as saproxylic beetle species. The aim of this study was to explore effects of forest management and some ecological factors on saproxylic beetles in spruce dominated forests, in County of Östergötland in Sweden. Sampling was done by mounting 175 window traps in 35 study sites of different age, around the county. Results showed that nature reserves had the highest number of species, individuals, and threatened species, while production forest, 15-25 years old, had the lowest. Production forests, 65-85 years old, had similarities in species composition with nature reserves, probably due to historical reasons. To some extent, these kinds of forests provide habitat for threatened species at a landscape level and could provide habitat for more threatened species in the future, with the right management. Quantity and quality of dead wood, basal area/ha, and vegetation cover increased species richness and number of individuals. Suggestions to generate a successful long-term conservation is to increase total amount of dead wood, improve diversity of dead wood, leave more large-sized trees during retention and a mixture of tree species in production forests. This will probably aid species dependent on later successional stages, increase vegetation complexity, habitat heterogeneity, and probably increase both number of individuals- and saproxylic beetle species in production forests in the future. Keywords: Composition; Conservation management; County of Östergötland; Ecological variables; Forest management; Saproxylic beetle species; Species richness; Spruce forests. 2 Introduction Old growth forests are continuing to decrease, due to our growing population’s rising demand for forest products, leading to deforestation and conversion to production forests (Fox, 2000; Kulha et al., 2020; Paillet et al., 2010). The long period of intensive forest management has created production forests consisting of even-aged, even-structured trees of different successional stages, with less volume and a less diverse quality of dead wood compared to old growth forest (Koivula & Vanha-Majamaa, 2020; Similä et al., 2003). This is problematic since old growth forests provide ecosystem services, such as soil protection, air and water purification, wildlife habitat, noise control, various types of recreation, and carbon storage (Cannell, 1999; Huettl & Zoettl, 1992; Keith et al., 2014; Luyssaert et al., 2008). Carbon storage in production forests compared to old growth forests is a subject constantly up for debate, where some scientists have argued that production forests store more carbon than old growth forests when including both biomass and its use for biomaterials and bioenergy (Schulze et al., 2020). However, other scientists have argued that old growth forests store a much higher amount of carbon than production forests, working as a global carbon sink, potentially mitigating climate change (Kun et al., 2020; Luyssaert et al., 2008; Mildrexler et al., 2020; Rodríguez-Soalleiro et al., 2018). 3 Globally, boreal forests contribute to 33 % of Earth´s forested area, creating the largest terrestrial carbon source, and provides important habitat for a lot of forest-dependent species (Jacobsen et al., 2020). However, boreal forests are an important source of timber and pulp wood, causing deforestation which leads to habitat loss and fragmentation, generating a major threat to biodiversity (Aune et al., 2005; Kouki et al., 2001; Pohjanmies et al., 2017; Seibold et al., 2015) Today, species dependent on large trees, forest cover continuity, dead wood and different stages of decaying wood have a particularly high risk of extinction (Paillet et al., 2010; Seibold et al., 2015; Söderström, 1988). In Sweden, human activities have changed the landscape on a large scale since beginning of 1930, for instance replacing old-growth forests with production forests (Björse & Bradshaw, 1998; Dahlström et al., 2006). Today, 8.7 % of Sweden’s forest area is formally protected forests, consisting of national parks, nature reserves, habitat protection areas, eco parks and Natura 2000 areas (Naturvårdsverket, 2020). In total, around 60 000 species exist in Sweden today, whereas 50 % are estimated to live in forests, and 50 % of all red listed species are estimated to live in forests, demonstrating that deforestation is a big threat to biodiversity (Eide et al., 2020; SLU Artdatabanken, 2020). However, only 1 % of forest landscape in Sweden have been identified as woodland key habitats (WKH), where red-listed species occur or may occur, most of those are small and isolated patches (Aune et al., 2005). To aid forest-dependent species relying on dead wood for survival, forest companies in Sweden have been required to leave some dead wood in harvested stands, since the mid-1990s (Gustafsson et al., 2010; Jonsell & Weslien,