| In light of multiple threats to forest biodiversity, the effective management of protected forests to maintain biodiversity is crucial. However, robust, long-term evaluations of forest conservation management are lacking. In southern Scandinavia, oak forests are particularly important for biodiversity of numerous taxa, yet they have seen drastic declines and are in need of proper management.
Twenty-two years ago, The Swedish Oak Project set out to experimentally evaluate the effect of conservation-oriented thinning contrasted with a hands-off, minimal intervention approach on oaks and several associated organism groups in 25 mixed oak forests (oaks growing among other trees) across the varied landscape of southern Sweden. Using a statistically robust before-after, control-impact (BACI) design of paired intervention and control plots allowed the project to draw strong conclusions on the effects of the two management alternatives. The results were varied, interesting, and valuable for practical conservation management, but they described primarily the short-term responses of the species groups (for a detailed Swedish website designed for outreach, see “Ekprojektet” https://www.gu.se/forskning/ekprojektet).
One of the groups which responded most positively to thinning was the wood-living beetles, one of the most ecologically important, diverse and threatened species groups in Sweden. In addition, results showed that the diversity of beetles, especially red-listed beetle species, was strongly influenced by the surrounding landscape. A small-scale follow-up study indicated that the beetles were still benefitting from the thinning 10 years later. However, after 20 years the thinned plots have seen much regrowth, while the minimal intervention plots have experienced natural dynamics, and the remaining effects are not clear. At the same time, the surrounding landscapes have also changed over the 20 years.
The aim of the current project is to do a rare 20-year follow-up of these results. Beetles will be re-sampled on all sites on which they were previously sampled, using the same methodology to allow comparisons across the years. This will provide important, actionable guidance to the practical conservation management of oak forests, and what is needed to preserve an important part of forest biodiversity.
The overall goals of the project are to:
1) Experimentally evaluate the 20-year response to conservation-oriented thinning of wood-living beetles in mixed oak forests in southern Sweden
2) Evaluate the need for continuous management vs a large, single intervention for wood-living beetles in these forests
3) Determine the effect of landscape variables on beetle diversity, and evaluate potential interactions between management outcomes and landscape context. |