Conservation of saproxylic species : an evaluation of set-asides and substrates in boreal forests

Sammanfattning: Forest management has altered the prerequisite of many species in forest landscapes. The new, more conservation-oriented forest management includes a range of different strategies that aim to prevent losses of biodiversity. Evaluating these strategies is essential in order to identify where they might fall short of their aims and to identify where to make any necessary improvements. In this thesis the importance of different conservation strategies is evaluated in terms of what they might contribute to the conservation of beetles dependent on deadwood. Furthermore, patterns of biodiversity and mechanisms that affect biodiversity are explored. In one study, species richness, composition and substrate characteristics were compared in three conservation strategies: nature reserves, woodland key-habitats and retention patches; and old managed forests that had not been set-aside. In a second study, high-cut stumps and other retained dead wood in clear-cuts were evaluated for their importance in the recruitment of the red-listed beetle Peltis grossa at the landscape level. A third study explored species richness co-variation, surrogate capacity and beta-diversity among bryophytes, lichens, saproxylic beetles and dead wood. A fourth study examined the priority effects among beetles and fungi colonizing high stumps in clear-cuts over a period of 15 years. Overall, woodland key-habitats were found to have a high conservation value in terms of species richness, richness of red-listed species, and diversity of dead wood. Reserves had the highest dead wood diversity; old managed forests had a relatively high number of red-listed species; and retention patches deviated in species composition. Leaving sun-exposed, coarse wood, which eventually develops into brown-rotten wood due to the fungi Fomitopsis pinicola, in a late stage of decay appeared to be a particularly efficient conservation strategy for P. grossa. The third study showed that the richness of red-listed lichens and bryophytes can be used to indicate each other's presence, and dead wood diversity appeared to be an efficient surrogate for beetles and bryophytes. A study of priority effects revealed that two early-colonizing species, Hylurgops palliatus and F. pinicola, positively affected the later colonizing species, P. grossa, whereas Monochamus sutor had a negative effect.

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