Ann Kraut will defend her doctoral thesis titled "Conservation of wood-inhabiting biodiversity – seminatural forests as an opportunity" on 11 May 2016 at 10.15 at Vanemuise 46-301.
Supervisor: juhtivteadur Asko Lõhmus, PhD (TÜ ÖMI)
Opponent: professor Thomas Ranius, Swedish University of Agricultural Sciences, Rootsi
Summary: Dead-wood is an essential part of forests, that provides habitat for a quarter of all forest species. Intensive management for timber production reduces its amount up to ten times and consequently endangers half of dead-wood dependent species. Semi-natural forestry, which is based on natural regeneration and multiple forest values, might provide better opportunities for deadwood inhabiting biodiversity. This thesis describes the habitat value of Estonian forest environments created by semi-natural forestry. Old growth sites had very variable structure across as well as within different forest site types and the volumes of deadwood in the studied hemiboreal forests exceeded published values for south-boreal and north-temperate zones. Beetle assemblages were clearly segregated between dry-boreal pine and spruce-mixedwood forests, and swamps had a distinct bird assemblage. In mature stands of the FSC-certified state forests several structural attributes of biodiversity importance were available similarly to old growth stands, mainly because of natural regeneration and moderate thinning intensity. However, there were large reductions in some important structures: very large trees (both live and dead), all late-successional deciduous trees, and logs in late stages of decay. Beetle and bird assemblages in these forests appeared to be smaller, more homogenous subsets of old-forest assemblages. Deadwood volumes on clear-cuts were much higher than reported for the Nordic intensive forestry. Yet, although natural renewal techniques retained large logs, their subsequent decay was accelerated and final felling greatly reduced snag abundance. The mortality of retained live trees improved the supply of standing and downed deadwood to some extent. Clearly impoverished beetle assemblages on cutovers were not detected, even after harvesting half of logging residues. This may also explain why threshold relationships were not detectable for any beetle species separately.