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Discussion & conclusion

Discussion

Similarities in saproxylic beetle species composition between production forests 65-85 years old and nature reserves have been reported in earlier studies. Explanations have been: matching diversity of dead wood, or that negative effects of production forest might partly be alleviated due to historical similarities. In this study, there were no matching diversity between the foresttypes, however, they do have historical similarities. Therefore, the historical similarities is probably the reason for the similarities in composition. 

Results showed a low number of individuals, saproxylic beetle species in clear-cuts, as well as a different species composition. Previously studies found the same pattern, and argued that the differences depended on the reduced amount of dead wood, and the changed habitat/microclimatic conditions. My results indicate on the same thing, since clear-cuts had a lower amount of dead wood, a lower amount of large-sized dead wood, and a lower diversity of decaying dead wood than nature reserves and old reserves. Despite a low number of species, there were some red-listed species in this study, only found in clear-cuts, indicating that a clear-cut with suitable substrates could be beneficial for saproxylic beetles. Further, most of the red-listed species found in clear-cuts were connected to deciduous trees, for example Xyletinus pectinatus, Cerylon deplanatum, and Xylotrechus antilope, showing the importance of leaving deciduous trees.

Conclusion

Old forests provided habitat for a higher number of saproxylic beetle species and individuals than younger forests, probably because they comprised substrates important for species dependent on both late- and early successional stages. Additionally, production forests 65-85 years old are important for conservation management since they show a potential to support threatened saproxylic beetle species with habitat in the future, if left unaffected. The similarities are probably due to historical reasons. Quantity and quality of dead wood, as well as canopy openness are ecological variables important to increase number of individuals, while basal area/ha, vegetation cover and type of dead wood are important for species richness and amount of biomass. Therefore, to generate a successful conservation in a long-term, both an increase in total amount of dead wood, and diversity of dead wood together with a mixture of tree species must be improved in production forests.


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Last updated: 05/14/21