Targets for maintenance of dead wood for biodiversity conservation based on extinction thresholds

Abstract

Forestry decreases the amount of dead wood, thereby threatening the persistence of many saproxylic (wood-living) organisms. This article discusses how targets for efforts to maintain and restore dead wood in managed forest landscapes should be defined. Several studies suggest extinction thresholds for saproxylic organisms. However, because the thresholds differ among species, the relationship between species richness and habitat amount at the local scale is probably described by a smoothly increasing curve without any distinct threshold. The most demanding species require amounts of dead wood that are virtually impossible to reach in managed forests. This means that unmanaged protected forests are needed. In managed forests, conservation efforts should focus on the landscape scale and on certain types of dead wood, but it is impossible to come up with any particular amount of dead wood that is desirable at the forest stand level.

Keywords:

• Beetles
• ecological thresholds
• occurrence patterns
• saproxylic
• species richness

Stig Larsson and Martin Schroeder made valuable comments on the manuscript. Support for this project came from the project “Predicting extinction risks for threatened wood-living insects in dynamic landscapes”, financed by the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning, the project “Conservation of biodiversity in managed forests” financed by the Faculty of Forestry at the Swedish University of Agricultural Sciences (SLU), Stiftelsen Lars Hiertas Minne, and a grant from the Natural Sciences and Engineering Research Council of Canada to L. F.