Species richness and abundance of saproxylic beetles in power-line corridors: effects of different management practices
Master thesis
Permanent lenke
http://hdl.handle.net/11250/277756Utgivelsesdato
2015-02-25Metadata
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- Master's theses (INA) [593]
Sammendrag
Beetles (Coleoptera) are a major component of forest biodiversity. Approximately 900 of the 3558 known beetle species in Norway are facultative or obligate saproxylic, that is, directly or indirectly dependent on dead wood. Saproxylic beetles are considered vulnerable in the Norwegian forest landscape, due to modern forestry practices that typically reduce the abundance of dead wood. Establishment and maintenance cutting of power-line corridors resembles clear-cutting of forest. However, after cutting, all the woody biomass is usually left behind in the power-line corridors, and thus dead wood accumulate in the corridors. The aim of this study was to investigate whether power-line clearings can provide suitable habitats for saproxylic beetles, and if abundance and richness was influenced by management practice. This was done by carrying out a large-scale field experiment at 19 sites in southeast Norway, with three different treatments (‘cut’ where the biomass was left in the treatment after cutting , ‘cut and removed’ where the biomass was removed from the treatment after cutting and ‘uncut’ where the trees were not cut). Beetles were sampled with flight interception traps: at each site, three traps were deployed in late spring in each treatment. The traps sampled beetles continuously throughout the summer 2013, and sampled individuals were collected once a month and brought to the lab for species identification. In total 29 298 beetles were sampled and identified to 856 species. 22 105 beetle individuals with 420 species were classified as saproxylic. Saproxylic beetle abundance was positively affected by the increasing amount of dead wood in ‘cut and removed’ and ‘uncut’, while in ‘cut’ treatments there was a threshold level. 7189 beetle individuals with 436 species were classified as not saproxylic. The abundance of not saproxylic beetles was low in all treatments, highest in ‘cut’ thereafter ‘cut and removed’ and lowest in the ‘uncut’ treatments. There were no specific correlations with increasing amount of dead wood in the treatments. Species richness of saproxylic beetles was high while not saproxylic species richness was low in all treatments. There were positive effects of sun-exposure for both saproxylic and not saproxylic beetles in ‘cut’ and ‘cut and removed’ treatments while in ‘uncut’ treatments the species richness was not affected by sun-exposure.
My results suggest that frequent cutting and no biomass removal of early successional forest in power-line corridors prevent the loss of dead wood dependent beetles.