Abstract
Restoration of habitats is critically important in preventing full realization of the extinction debt owed as a result of anthropogenic habitat destruction. Although much emphasis has been placed on macrohabitats, suitable microhabitats are also vital for the survival of most species. The aim of this large-scale field experiment was to evaluate the relative importance of manipulated microhabitats, i.e., dead wood substrates of spruce (snags, and logs that were burned, inoculated with wood fungi or shaded) and macrohabitats, i.e., stand types (clear-cuts, mature managed forests, and forest reserves) for species richness, abundance and assemblage composition of all saproxylic and red-listed saproxylic beetles. Beetles were collected in emergence traps in 30 forest stands in 2001, 2003, 2004 and 2006. More individuals emerged from snags and untreated logs than from burned and shaded logs, but species richness did not differ among substrates. Assemblage composition differed among substrates for both all saproxylics and red-listed saproxylic species, mainly attributed to different assemblage composition on snags. This suggests that the practise of leaving snags for conservation purposes should be complemented with log supplementation. Clear-cuts supported fewer species and different assemblages from mature managed forests and reserves. Neither abundance, nor species richness or assemblage composition differed between reserves and mature managed forests. This suggests that managed stands subjected to selective cutting, not clear-felling, maintain sufficient old growth characteristics and continuity to maintain more or less intact assemblages of saproxylic beetles. Thus, alternative management methods, e.g., continuity forestry should be considered for some of these stands to maintain continuity and conservation values. Furthermore, the significantly higher estimated abundance per ha of red-listed beetles in reserves underlines the importance of reserves for maintaining viable populations of rare red-listed species and as source areas for saproxylic species in boreal forest landscapes.
Highlights
Human activities have caused substantial fragmentation, loss and degradation of habitats worldwide [1,2]
We address the following questions: 1) Are some substrates more important than others for saproxylic species in general and red-listed saproxylic beetles in particular? We ask if snags, the most commonly used substrate for conservation purposes, supports a higher richness and abundance of saproxylic beetles including redlisted beetles but we evaluate the complementarity of different substrate types
Species richness and abundance The total abundance of saproxylic species per stand differed among substrates but not among forest types and there was no significant interaction between these factors (Table 1)
Summary
Human activities have caused substantial fragmentation, loss and degradation of habitats worldwide [1,2]. In the short-term, many species have survived the initial decrease in habitat availability, but it is likely that an extinction debt is yet to be paid [3], with many species in decline. Without intervention, these species may become extinct. Managed habitats present an opportunity for conservation and production to co-exist through the restoration of microhabitats, which may improve both spatial and temporal connectivity for many species. Conservation of species with specific resource requirements, such as many invertebrates, might be achieved through retaining or restoring microhabitat elements [4,5,6]. Many forms of agriculture completely transform landscapes, silvicultural systems often provide the opportunity to retain many elements of the original landscape, so they are more suitable for this blend of conservation and production
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