Lukas Cizek

Volatile organic compounds (VOCs) emitted by deadwood are increasingly recognised as key olfactory cues used by saproxylic beetles to locate suitable substrates, yet their role during colonisation remains poorly understood. To address this, we quantified VOC emissions and beetle assemblages while experimentally disentangling the main ecological drivers of the deadwood volatilome (tree species, sun exposure). We exposed 1200 freshly cut branches of oak, beech, spruce, and pine across Central Europe. To mimic natural variation in deadwood and disturbance, bundles were either sterilised (reducing endogenous fungi), inoculated with a brown rot fungus ( Fomitopsis pinicola ) or a white rot fungus ( Fomes fomentarius ), or burned. From each bundle, we sampled 448 substances, 89 of which were identified as VOCs, and reared 134 saproxylic beetle species. Broadleaf and conifer species emitted distinct VOC profiles that matched beetle tree-type preferences. In conifers, bark beetles, longhorn beetles, and jewel beetles were associated with different chemical cues, whereas taxonomic separation was not observed in broadleafs. Although treatments altered VOC composition, they did not explain beetle colonisation. Our study shows that VOCs emitted during early decay are associated with distinct beetle assemblages. The VOC composition varied with tree species and treatments, indicating that chemical variation reflects the influence of multiple ecological factors. These findings suggest that tree-species diversity enhances chemical heterogeneity in deadwood, which is linked to broader beetle assemblages. Forest conservation efforts may therefore need to consider the role of chemical variation in deadwood, as it could influence saproxylic colonisation and biodiversity management.

Aim: Understanding temporal patterns of vegetation change is crucial for assessing the ecological integrity of forest understoreys under shifting management and climate regimes. This study investigates long‐term (60‐year) and short‐term (10‐year) changes in species composition, functional traits, and phylogenetic diversity (PD) of understorey communities in Central European floodplain forests. The goal is to determine how different temporal scales capture ecological dynamics and to identify trait‐based mechanisms underlying community shifts. Location: The research was conducted in floodplain forests across Central Europe, encompassing oak, ash, hornbeam, and willow‐dominated stands distributed along a gradient of soil moisture availability. Methods: We analyzed repeated vegetation plot records across two temporal scales. Changes in species richness, functional diversity (FD), and PD were quantified. Species‐level shifts were linked to plant traits such as height, seed mass, and leaf dry matter content (LDMC), with analyses stratified by forest type. Results: Over 60 years, species richness and PD declined, driven by the loss of phylogenetically distinct light‐demanding specialists and an increase in tall woody generalists with conservative strategies. FD remained stable but showed directional trait shifts. In contrast, the 10‐year data showed limited changes in diversity indices, despite continued increases in some woody species and temporary gains of specialists in drier hornbeam stands. Trait–abundance correlations indicated that taller species with high LDMC or heavier seeds were favored under conditions of canopy closure and drought. Invasive species also increased in abundance over the 60‐year period, whereas short‐term trends exhibited weaker signals. Conclusions: Long‐term data revealed compositional and trait‐based transformations missed in short‐term assessments, emphasizing the value of extended temporal monitoring. Trait–environment interactions varied among forest types, reflecting site‐specific drivers such as differences in moisture conditions. These findings highlight the need for temporally informed forest management strategies that promote resilience by addressing both species impoverishment in the forest understorey and trait‐based filters.

The insect biodiversity crisis affects diverse cultural landscapes as well as natural and semi-natural habitats. Accordingly, the effectiveness of protected areas in conserving insect communities needs to be evaluated. We employed photo-interpretation of aerial photographs from the past (1938-1947) and present (2014-2019) to analyse changes in natural habitats with diverse canopy cover in seven long-term protected areas (jointly called 'reserves') in the Czech Republic, Central Europe, and evaluated potential links between these changes and butterfly and moth (Lepidoptera) declines. We observed a marked decrease in habitat heterogeneity, largely due to the expansion of closed-canopy forests at the expense of semi-open habitats (e.g. forest steppes, open woodlands) and open grasslands. An analysis of faunistic records of 162 species of butterflies and 160 species of macro-moths before and after 2000 showed that, on average, the reserves have experienced losses of 26% of butterfly species and 19% of moth species. Trait-based analyses suggested that the losses were associated with particular life-history traits. Non-generalist butterflies with a short period of seasonal flight activity, and moths associated with grasslands and with non-feeding adults, had a greater probability of going missing (meaning potentially locally extinct) in the reserves. These findings suggest that conservation efforts should prioritise active management that aims to restore habitat heterogeneity in order to mitigate the ongoing trend of insect decline.

Volatile organic compounds (VOCs) emitted by deadwood are increasingly recognised as key olfactory cues used by saproxylic beetles to locate suitable substrates. However, how beetle communities respond to these cues during the colonisation of deadwood remains poorly understood. To address this gap, it is essential to quantify both VOC emissions and beetle assemblages, and to experimentally disentangle the main ecological drivers of the deadwood volatilome (i.e., tree species, sun exposure). To explore the potential role of VOCs on saproxylic beetle colonisation, we exposed 1200 freshly cut branches of oak, beech, spruce, and pine across Central Europe. To mimic natural variation in deadwood and disturbance processes, the bundles were experimentally manipulated either by sterilisation (to reduce endogenous fungi), fungal inoculation with a brown rot fungus ( Fomitopsis pinicola ), a white rot fungus ( Fomes fomentarius ), or burning. From each deadwood bundle, we sampled 448 substances, 89 of which were identified as VOCs and reared 134 saproxylic beetle species. We observed distinct VOC profiles emitted by broadleaf and conifer species, aligning with the beetles’ tree-type preferences. In conifers, bark beetles, longhorn beetles, and jewel beetles were associated with different chemical cues, whereas beetle taxonomic separation was not observed in broadleaf species. Although experimental treatments altered VOC composition, they could not explain beetle colonisation patterns. Our study highlights that VOCs emitted during the early decay stage of deadwood are associated with distinct saproxylic beetle assemblages. VOC composition varied across tree species and treatments, suggesting that chemical variation reflects multiple ecological factors. These findings indicate that deadwood diversity, particularly in tree species, contributes to chemical heterogeneity, which is linked to broader beetle assemblages. Forest conservation efforts may therefore need to consider the role of chemical variation in deadwood, as it could influence colonisation patterns of saproxylic beetles and affect the success of biodiversity management strategies.

The ability to locate and colonise ephemeral deadwood resources is crucial to saproxylic beetle assemblages. Saproxylic beetles locate suitable substrates mainly through visual cues and via olfactory cues emitted by deadwood, other insects and fungi. For the conservation of saproxylic beetles, it is essential to understand which abiotic and biotic factors most significantly influence their habitat requirements when locating suitable substrates. In a field experiment, in sunny and shaded plots, we exposed 400 bundles of freshly cut deadwood, each consisting of three logs with a combination of different tree species and treatments (i.e., fungi inoculation), mimicking biotic interactions. We sampled arriving saproxylic beetles via sticky traps directly applied on deadwood to evaluate the effect of sun exposure and the biotic interactions on arriving saproxylic beetles. We found higher species numbers and abundance of saproxylic beetles under shaded than sunny conditions, but we detected no effect on the standardised number of species (diversity). However, we observed a shift in species diversity from sunny to shaded conditions from early to late season. Beetle assemblages differ between shaded and sun‐exposed deadwood. Treatments (fungi inoculation, sterilisation and burning) did not affect the arriving saproxylic beetles. Our results suggest that saproxylic beetles' attraction to freshly cut deadwood is mainly driven by sun exposure rather than biotic interactions, despite assumed close associations between beetles and fungi. To protect the full spectrum of saproxylic beetle species, we recommend maintaining sunny and shaded areas, as each provides unique habitats supporting different assemblages.

Veteran and ancient trees are key structures sustaining biodiversity in wooded landscapes. Their value depends on tree‐related microhabitats (TreMs) such as hollows, cracks and other structures related to wounds and wood decay. Decline and loss of veteran trees results in the loss of TreMs thus threatening the biodiversity associated with them. Veteranisation , that is, interventions aimed at creating or accelerating formation of rare TreMs in live trees, are thus increasingly applied to bridge gaps in habitat continuity and sustain the biodiversity associated with veteran trees. Several studies investigated the use of artificially created TreMs by various organisms. No study has, however, investigated saproxylic beetles attracted to freshly veteranised trees, and how different veteranisation techniques affect attractivity of veteranised trees to saproxylic beetles. We veteranised 48 sessile oaks using two types of deep and two types of shallow cuts and trapped saproxylic beetles on the veteranised and control trees in the first season after the intervention. The sampling yielded 280 species (6171 individuals) of saproxylic beetles, including 64 that are threatened. Veteranised trees attracted more abundant and diverse communities than control trees. Community composition differed between shallow and deep cuts and between the two types of deep cuts. Freshly veteranised trees thus attract diverse and abundant communities of saproxylic beetles consisting mainly of species potentially exploiting the wounds. The high proportion of threatened species, often associated with old oaks, suggests that veteranised trees benefit even some threatened saproxylic biodiversity already during the first year after the veteranisation.

Aim: Understanding the processes that structure biological communities along environmental gradients remains one of the main aims of ecological research. A leading question is how differences in species composition between sites, that is, β‐diversity, change in habitats ordered along environmental gradients and how such changes vary with species relative abundances. The existing literature remains descriptive, mostly comparing communities from different parts of a gradient, but not tracking sequential changes of β‐diversity along the entire gradient.Location: Temperate deciduous forests in Central Europe.Taxa: Saproxylic beetles.Methods: We applied a generalized concept of Hill numbers to data on the distribution of saproxylic beetles to test (i) whether community dissimilarities correlate with dissimilarities in major environmental variables (canopy openness, tree diameter and tree genus) and (ii) which mechanisms explain sequential changes of β‐diversity along these environmental gradients. Furthermore, we illustrate changes in the mean (α‐diversity) and total (γ‐diversity) number of species along the gradients.Results: Dissimilarities in saproxylic beetle communities were positively correlated with dissimilarities in all studied environmental variables. Changes in β‐diversity along the gradients differed for different weighting of rare, common and dominant species, with rare and dominant species always showing opposite trends. β‐diversity increased simultaneously with increasing γ‐diversity when weight was given to dominant species. On the other hand, β‐diversity decreased when weight was given to rare species.Main conclusions: The different response of rare and dominant species indicates a similar importance of stochastic and deterministic processes in determining β‐diversity. Although the changes in β‐diversity detected along the environmental gradients were relatively slight, major community dissimilarities were found when comparing communities in different locations of the environmental gradients.

European forests are facing a rapid decline in light‐demanding biota. This has prompted active interventions to re‐establish and maintain partial habitat openness in protected areas. Managers of protected areas, however, need substantially more scientific evidence to support their decisions on where, when and how to intervene. We investigated the importance of spatial continuity of open forest habitats in different years of succession, using six pairs of experimental clearings established in the formerly open, oak‐dominated forests of the Podyji National Park (Czech Republic). In each pair, one clearing was connected to the forest edge, while the other was isolated in closed forest. We sampled butterflies (74 spp.), moths (435 spp.), saproxylic beetles (465 spp.) and vascular plants (567 spp.) on the 12 clearings during the first 5 years of succession. We then compared species richness, abundance and composition of the four taxa between the two clearing types and along the succession. All studied insect groups were substantially more species rich and more abundant in connected than in isolated clearings. Species composition of plants, moths and butterflies differed between the clearing types. The number of species of all studied taxa generally increased from the first to the second or third year after cutting; species composition of all taxa differed among years. This suggests rapid changes in habitat quality and thus limited time for colonisation by light‐demanding organisms. Synthesis and applications. Our results offer an evidence that spatial connectivity and rapid temporal dynamics are important habitat features for light‐demanding insects. Attempts to create or restore habitats for light‐demanding forest biota should take into account that: (a) Insects benefit from direct connection of new open patches to open habitats or flight corridors such as forest edges. (b) Considering plants, the optimal solution is to connect newly created open forest habitats to existing habitats with established biota of high conservation value. (c) Interventions should be carried out within short time intervals, that is within years rather than decades. (d) A fine mosaic of interconnected, open woodland patches in various successional stages is more beneficial than a single large patch with a single successional stage.