While climate change has increased interest in the influence of microclimate on many organisms, species inhabiting deadwood have rarely been studied. Here we explore the relationships between characteristics of forest stands, deadwood and microclimate, and analyse how the microclimate inside deadwood affects the occurrence of wood-living organisms, exemplified by the red-listed beetle Tragosoma depsarium. Some of the measured deadwood and forest variables explain much of the variation in temperature, but little of humidity aspects of the microclimate within deadwood. Several variables known to influence habitat quality for deadwood-dependent species were found to correlate with microclimate viz.: warmer conditions in standing deadwood and open canopy than in downed logs and under a closed canopy; higher humidity and more stable daily temperatures in shaded habitats and in downed and large-diameter wood, than in sun-exposed locations and standing, small-diameter wood.
T. depsarium occupancy and abundance were negatively correlated with daily temperature fluctuations, and positively related to spring and summer temperature and humidity. This can explain why the species occurred more frequently in deadwood items with characteristics associated with these microclimatic conditions, i.e. downed large-diameter logs occurring in open conditions. Since microclimatic conditions are important for T. depsarium and related to several habitat characteristics, we expect the effects of these characteristics to interact with each other, and for species’ habitat requirements to vary due to local and regional climate conditions, and to changes due to climate warming.