Wood-living beetle diversity and Swedish forest management

• Main Author: Gran, Oskar
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2022
• Subjects: biodiversity; forestry; harvest; insects; landscape; management; Fennoscandian
• Online Access: https://hdl.handle.net/2077/71971

Humans have impacted Fennoscandian forests for thousands of years, through grazing, burning, and since the industrial revolution increasingly through efficient industrial forestry. These impacts have changed the composition and structure of these forests, by reducing forest age, simplifying forest structure, and reducing the amount of broadleaved trees, among other things. To achieve a forestry model that is sustainable, the consequences of these changes on forest biodiversity need to be evaluated. In this thesis, I focus on saproxylic (wood-living) beetles, within south-central Swedish forestry and forest conservation. This ecological group utilizes dead wood in various forms and is species-rich (1,200 Swedish species), threatened (400 red-listed Swedish species), ecologically diverse, and of high conservation and management relevance. In Paper I, I test the 10-year effect of conservation-oriented thinning on oakassociated saproxylic beetles in 8 pairs of 1-hectare oak-dominated forest plots spread across southern Sweden. For each pair, one plot was treated with thinning in 2002/2003, and one was left as a minimal intervention reference plot. Beetles were sampled shortly before, shortly after, and in my study, 10 years after thinning. The number of beetle species in the thinning plots relative to the reference plots increased slightly and non-significantly shortly after thinning, but significantly 10 years later, equaling around a 33% increase. In Paper II, I compare the diversity of saproxylic beetles and several ecological subgroups between a common spruce forestry stage (young pre-commercially thinned stands), and small broadleaf-dominated unmanaged semi-natural stands (Woodland Key Habitats). Ten pairs of stands of the two forest types were used, spread across Jönköping county in southern Sweden. While the local (alpha) diversity of beetles was similar between the forest types, the total (gamma) diversity was higher for red-listed and broadleaf-associated species in the Woodland Key Habitats. Further, the ...