Wood decomposition is a central process contributing to global carbon and nutrient cycling. Quantifying the role of the major biotic agents of wood decomposition, i.e. insects and fungi, is thus important for a better understanding of this process. Methods to quantify wood decomposition, such as dry mass loss, suffer from several shortcomings, such as destructive sampling or subsampling. We developed and tested a new approach based on computed tomography (CT) scanning and semi-automatic image analysis of logs from a field experiment with manipulated beetle communities. We quantified the volume of beetle tunnels in wood and bark and the relative wood volume showing signs of fungal decay and compared both measures to classic approaches. The volume of beetle tunnels was correlated with dry mass loss and clearly reflected the differences between beetle functional groups. Fungal decay was identified with high accuracy and strongly correlated with ergosterol content. Our data show that this is a powerful approach to quantify wood decomposition by insects and fungi. In contrast to other methods, it is non-destructive, covers entire deadwood objects and provides spatially explicit information opening a wide range of research options. For the development of general models, we urge researchers to publish training data.

Bavarian Forest National Park Freyungerstrasse 2 94481 Grafenau Germany

Berchtesgaden National Park Doktorberg 6 83471 Berchtesgaden Germany

Ecosystem Dynamics and Forest Management Group Technical University of Munich 85354 Freising Germany

Faculty of Biological Sciences Institute for Ecology Evolution and Diversity Goethe University Frankfurt 60438 Frankfurt am Main Germany

Faculty of Biology Department of Ecology Animal Ecology Philipps Universität Marburg Karl Von Frisch Strasse 8 35032 Marburg Germany

Field Station Fabrikschleichach Animal Ecology and Tropical Biology Biocenter University of Würzburg Glashüttenstrasse 5 96181 Rauhenebrach Germany

Forest Nature Conservation Georg August University Göttingen 37077 Göttingen Germany

Forest Nature Conservation Northwest German Forest Research Institute NW FVA 34346 Hann Münden Germany

Laboratory of Environmental Microbiology Institute of Microbiology of the Czech Academy of Sciences Videnska 1083 14220 Praha 4 Czech Republic

MITOS GmbH Lichtenbergstrasse 8 85748 Garching Germany

Terrestrial Ecology Research Group Technical University of Munich 85354 Freising Germany

USDA Forest Service Southern Research Station Athens GA USA

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