Microclimate and habitat heterogeneity as the major drivers of beetle diversity in dead wood

Abstract

1. Resource availability and habitat heterogeneity are principle drivers of biodiversity, but their individual roles often remain unclear since both factors are usually correlated. The biodiversity of species dependent on dead wood could be driven by either resource availability represented by dead-wood amount or habitat heterogeneity characterized by dead-wood diversity or both. Understanding their roles is crucial for improving evidence-based conservation strategies for saproxylic species in managed forests. 2. To disentangle the effects of dead-wood amount and dead-wood diversity on biodiversity relative to canopy openness (microclimate), we experimentally exposed different amounts of logs and branches of two different tree species representing a gradient of dead-wood diversity in 190 sunny and shady forest plots. During the 3 years after exposing dead wood, we sampled saproxylic beetles, which are together with fungi the most diverse and important taxonomic group involved in decomposition of wood. 3. The composition of saproxylic beetle assemblages differed clearly between shady and sunny forest plots, with higher richness in sunny plots. Both dead-wood amount and deadwood diversity positively and independently affected species richness of saproxylic beetles, but these effects were mediated by canopy openness. In sunny forest, species richness increased with increasing amount of dead wood, whereas in shady forest, dead-wood diversity was the prevailing factor. 4. The stepwise analysis of abundance and species richness, however, indicated that effects of both factors supported only the habitat-heterogeneity hypothesis, as the positive effect of high amounts of dead wood could be explained by cryptic variability of dead-wood quality within single objects. 5. Synthesis and applications. As canopy openness and habitat heterogeneity seem to be the major drivers of saproxylic beetle diversity in temperate forests, we recommend that managers aim to increase the heterogeneity of dead-wood substrates under both sunny and shady forest conditions. Intentional opening of the canopy should be considered in anthropogenically homogenized, dense forests. Specifically in temperate mixed montane forests, dead wood should be provided in the form of large logs in sunny habitats and a high diversity of different dead-wood substrates should be retained or created in shady forests.

The indicator side of tree microhabitats: A multi‐taxon approach based on bats, birds and saproxylic beetles

“…Compared to previous results (Paillet et al., ), the negative result for saproxylic beetles is more surprising, but may be due to the fact that most of the reserves we studied are relatively young and display relatively small amounts of favourable habitats and features compared to other European references (Bouget, Parmain, et al., ; Paillet, Pernot, et al., ). As a consequence, stands may still be in an accumulation phase where light conditions are probably not diverse enough to favour both forest specialists and light‐demanding species at a small scale (see e.g., Bouget, Larrieu, et al., ; Seibold et al., for saproxylic beetles) and the potential effect of microhabitats or large structural elements may be masked by such unfavourable light conditions (Miklín et al., ). It is thus important to take the temporal dimension of this result into account and we may expect biodiversity to increase when the reserves would be mature enough to show spatial horizontal heterogeneity at the stand scale (Paillet, Pernot, et al., ).…”

Influence of canopy gaps on saproxylic beetles in primeval beech forests: a case study from the Uholka‐Shyrokyi Luh forest, Ukraine

“…In a second step, we used a similar model including the number of individuals (log) as explanatory variable for the species richness similarly to Seibold et al . (). By this, we tested whether effects on species richness were caused by a change in the abundance of saproxylic beetles.…”

Independent effects of host and environment on the diversity of wood‐inhabiting fungi

“…Despite the importance and diversity of wood‐inhabiting fungi, our understanding of the factors driving the spatial and temporal patterns of their diversity is limited. It has been suggested that characteristics of the colonized dead‐wood object (host) and the environment surrounding an object are important drivers of the diversity of wood‐inhabiting fungi (Heilmann‐Clausen et al., ; Seibold, Bässler, Brandl, et al., ; Seibold et al., and therein). However, how the host and the environment individually affect fungal diversity on dead‐wood objects is unknown (Bradford et al., ).…”

“…This correlation is not surprising as forest gap dynamics caused by anthropogenic disturbances, for example, logging, or natural disturbances, for example, windthrows, insects, fire or snow, is an important driver influencing the diversity of forest species across numerous taxa at the landscape scale (Swanson et al., ). Variation in canopy openness is physically correlated to changes in moisture and temperature regimes and to fluctuations of these variables also within a dead‐wood object (Scharenbroch & Bockheim, ; Seibold, Bässler, Brandl, et al., ). Variation in microclimate within dead wood can therefore have pronounced effects on the fungal community (Boddy & Heilmann‐Clausen, ; Pouska, Macek, Zíbarová, & Ostrow, ).…”