Patterns and drivers of deadwood volume and composition in different forest types of the Austrian natural forest reserves

Deadwood is an important structural feature in forests providing essential resources for various organisms. Both forest management and conservation are increasingly focusing on the integration of deadwood into forest management. Deadwood volume and composition are driven by forest type, stand age, natural tree mortality, tree species composition and harvesting intensity. Here, we used inventory data from 28 unmanaged natural forest reserves (NFR) in Austria to analyse the patterns and drivers of: (i) the volume of standing and lying deadwood, (ii) the diversity of deadwood in different forest types. Eight forest types are located in the investigated NFRs covering a wide range of vegetation types with altitudes of 140–1825 m asl. The volumes of living wood and deadwood differed markedly between forest types. The average deadwood volume per forest type ranged from 23 m3 ha−1 in larch forests to 109 m3 ha−1 in spruce-fir-beech forests. Likewise, deadwood diversity (species diversity as well as diversity in diameter classes and degree of decomposition) differed significantly among forest types, with the highest deadwood diversity found in beech and spruce forests and the lowest in hardwood floodplain forests, carbonate pine forests and larch forests. Our results show that volume and composition of deadwood vary greatly among different forest types. Regression models revealed that the availability of deadwood was mainly driven by tree- and stand related factors (e.g. forest type, diameter at breast height and volume of living stand), whereas site-related (e.g. altitude) and climatic factors (e.g. mean annual precipitation) had a minor influence. The variables tree species diversity, aspect and slope showed no significance and were therefore not integrated into the final model. This study provides insights into deadwood availability and diversity in NFRs on a national scale, providing reference data for unmanaged temperate forests and aiding decision-making in nature conservation and forest management, since NFRs are reference areas for close-to-nature forestry. © 2020