Facteurs-clés et seuils critiques à l’échelle du peuplement forestier pour les coléoptères saproxyliques dans une forêt à dominance de hêtre du sud de l’Allemagne

We studied the importance of five typical structural parameters (age, growing stock, breast height diameter, basal area of trees with cavities containing humus, dead wood volume) for saproxylic Coleoptera in relation to species richness and numbers of individuals in beech forest, using standard-time direct searches and window traps at 69 sampling plots (0.1 ha). Maximally selected two-sample statistics were used to identify the important parameters and calculate critical thresholds. For the factors specifi ed above we found significant correlations only for endangered species and those indicating pristine conditions. The only statistically significant factor was the amount of dead wood. For species, the critical threshold was found between 38 and 58 m3/ha and for numbers of individuals at 144 m3/haNous avons étudié en hêtraie l'importance de cinq paramètres structuraux typiques (âge, volume sur pied, diamètre à hauteur de poitrine, surface basale des arbres avec cavités contenant de l'humus, volume de bois mort) pour les coléoptères saproxyliques en relation avec la richesse spécifique et le nombre d'individus en utilisant la recherche directe en temps standardisé et des pièges à vitre dans 69 points-échantillons (0,1 ha). Des statistiques de rang dites «Maximally selected two-sample statistics» ont été utilisées pour identifier les paramètres importants et calculer les seuils critiques. Pour les facteurs spécifiés ci-dessus nous n'avons trouvé des corrélations significatives que pour les espèces menacées et celles indicatrices de conditions naturelles non perturbées. Le seul facteur statistiquement significatif fut la quantité de bois mort. Le seuil critique était de 38 à 58 m3/ha pour les espèces et de 144 m3/ha pour les nombres d'individu

Ambient and substrate energy influence decomposer diversity differentially across trophic levels.

The species-energy hypothesis predicts increasing biodiversity with increasing energy in ecosystems. Proxies for energy availability are often grouped into ambient energy (i.e., solar radiation) and substrate energy (i.e., non-structural carbohydrates or nutritional content). The relative importance of substrate energy is thought to decrease with increasing trophic level from primary consumers to predators, with reciprocal effects of ambient energy. Yet, empirical tests are lacking. We compiled data on 332,557 deadwood-inhabiting beetles of 901 species reared from wood of 49 tree species across Europe. Using host-phylogeny-controlled models, we show that the relative importance of substrate energy versus ambient energy decreases with increasing trophic levels: the diversity of zoophagous and mycetophagous beetles was determined by ambient energy, while non-structural carbohydrate content in woody tissues determined that of xylophagous beetles. Our study thus overall supports the species-energy hypothesis and specifies that the relative importance of ambient temperature increases with increasing trophic level with opposite effects for substrate energy

Arthropod communities in fungal fruitbodies are weakly structured by climate and biogeography across European beech forests

Aim The tinder fungus Fomes fomentarius is a pivotal wood decomposer in European beech Fagus sylvatica forests. The fungus, however, has regionally declined due to centuries of logging. To unravel biogeographical drivers of arthropod communities associated with this fungus, we investigated how space, climate and habitat amount structure alpha and beta diversity of arthropod communities in fruitbodies of F. fomentarius. Location Temperate zone of Europe. Taxon Arthropods. Methods We reared arthropods from fruitbodies sampled from 61 sites throughout the range of European beech and identified 13 orders taxonomically or by metabarcoding. We estimated the total number of species occurring in fruitbodies of F. fomentarius in European beech forests using the Chao2 estimator and determined the relative importance of space, climate and habitat amount by hierarchical partitioning for alpha diversity and generalized dissimilarity models for beta diversity. A subset of fungi samples was sequenced for identification of the fungus’ genetic structure. Results The total number of arthropod species occurring in fruitbodies of F. fomentarius across European beech forests was estimated to be 600. Alpha diversity increased with increasing fruitbody biomass; it decreased with increasing longitude, temperature and latitude. Beta diversity was mainly composed by turnover. Patterns of beta diversity were only weakly linked to space and the overall explanatory power was low. We could distinguish two genotypes of F. fomentarius, which showed no spatial structuring. Main conclusion Fomes fomentarius hosts a large number of arthropods in European beech forests. The low biogeographical and climatic structure of the communities suggests that fruitbodies represent a habitat that offers similar conditions across large gradients of climate and space, but are characterized by high local variability in community composition and colonized by species with high dispersal ability. For European beech forests, retention of trees with F. fomentarius and promoting its recolonization where it had declined seems a promising conservation strategy

Zweiter Beitrag zur Dytisciden- und Hydrophilidenfauna Nordbayerns (Col. Dytiscidae, Hydrophilidae)

Volume: 037Start Page: 5End Page: 1

Key factors and critical thresholds at stand scale for saproxylic beetles in a beech dominated forest, southern Germany

We studied the importance of five typical structural parameters (age, growing stock, breast height diameter, basal area of trees with cavities containing humus, dead wood volume) for saproxylic Coleoptera in relation to species richness and numbers of individuals in beech forest, using standard-time direct searches and window traps at 69 sampling plots (0.1 ha). Maximally selected two-sample statistics were used to identify the important parameters and calculate critical thresholds. For the factors specifi ed above we found significant correlations only for endangered species and those indicating pristine conditions. The only statistically significant factor was the amount of dead wood. For species, the critical threshold was found between 38 and 58 m3/ha and for numbers of individuals at 144 m3/ha.Facteurs-clés et seuils critiques à l’échelle du peuplement forestier pour les coléoptères saproxyliques dans une forêt à dominance de hêtre du sud de l’Allemagne. — Nous avons étudié en hêtraie l’importance de cinq paramètres structuraux typiques (âge, volume sur pied, diamètre à hauteur de poitrine, surface basale des arbres avec cavités contenant de l’humus, volume de bois mort) pour les coléoptères saproxyliques en relation avec la richesse spécifique et le nombre d’individus en utilisant la recherche directe en temps standardisé et des pièges à vitre dans 69 points-échantillons (0,1 ha). Des statistiques de rang dites «Maximally selected two-sample statistics» ont été utilisées pour identifier les paramètres importants et calculer les seuils critiques. Pour les facteurs spécifiés ci-dessus nous n’avons trouvé des corrélations significatives que pour les espèces menacées et celles indicatrices de conditions naturelles non perturbées. Le seul facteur statistiquement significatif fut la quantité de bois mort. Le seuil critique était de 38 à 58 m3/ha pour les espèces et de 144 m3/ha pour les nombres d’individus.Müller Jörg, Bussler Heinz. Key factors and critical thresholds at stand scale for saproxylic beetles in a beech dominated forest, southern Germany. In: Revue d'Écologie (La Terre et La Vie), supplément n°10, 2008. 4ème colloque sur la conservation des coléoptères saproxyliques, tenu à Vivoin (Sarthe – France) du 27 au 29 juin 2006 / Proceedings of the 4th symposium and workshop on the conservation of Saproxylic beetles, held in vivoin, sarthe department – France 27–29 June 2006. pp. 81-90

Learning From A Benign Neglect Strategy In A National Park: Response Of Saproxylic Beetles To Dead Wood Accumulation

Increasing demands for firewood owing to rising energy costs have accelerated discussions about the amount of dead wood needed for conservation. A sharp increase in dead wood caused by bark beetles in a German national park provides lessons for management of commercial and protected forests. We investigated the effects of dead wood due to bark beetle infestation as well as tree senility on abundance and richness of saproxylic species of beetles. Increasing amounts of spruce dead wood and opening of the canopy by bark beetles had positive effects on the abundance of host-generalist, conifer-specialist, and red-listed saproxylic beetles. Broadleaf specialists were positively associated with the amount of broadleaf dead wood and negatively associated with canopy openness. Gradient analysis of beetle assemblages revealed two major environmental axes: canopy openness and amount of dead wood. We found a threshold for community divergence at a canopy openness of 23% (confidence interval CI: 11-49) and at an amount of dead wood of 64m3ha-1 (CI: 35-160). Critically endangered species served as indicators of dense and open forests, but only when the amount of dead wood was high. Our results suggest that, to maintain saproxylic beetle assemblages, the amount of dead wood in commercial montane forests (at present ≈15m3ha-1) needs to be tripled, with a focus on broadleaf wood in dense stands and spruce wood in open stands. For large protected areas in Europe, our data suggest that bark beetle infestation and senescence without active forest management improves habitat conditions for saproxylic beetles. © 2010 Elsevier Ltd

Aus der M\ufcnchner Entomologischen Gesellschaft

Volume: 050Start Page: 90End Page: 10

Diversity and conservation of saproxylic beetles in 42 European tree species: an experimental approach using early successional stages of branches

Tree species diversity is important to maintain saproxylic beetle diversity in managed forests. Yet, knowledge about the conservational importance of single tree species and implications for forest management and conservation practices are lacking. We exposed freshly cut branch‐bundles of 42 tree species, representing tree species native and non‐native to Europe, under sun‐exposed and shaded conditions for 1 year. Afterwards, communities of saproxylic beetles were reared ex situ for 2 years. We tested for the impact of tree species and sun exposure on alpha‐, beta‐, and gamma‐diversity as well as composition of saproxylic beetle communities. Furthermore, the number of colonised tree species by each saproxylic beetle species was determined. Tree species had a lower impact on saproxylic beetle communities compared to sun exposure. The diversity of saproxylic beetles varied strongly among tree species, with highest alpha‐ and gamma‐diversity found in Quercus petraea. Red‐listed saproxylic beetle species occurred ubiquitously among tree species. We found distinct differences in the community composition of broadleaved and coniferous tree species, native and non‐native tree species as well as sun‐exposed and shaded deadwood. Our study enhances the understanding of the importance of previously understudied and non‐native tree species for the diversity of saproxylic beetles. To improve conservation practices for saproxylic beetles and especially red‐listed species, we suggest a stronger incorporation of tree species diversity and sun exposure of into forest management strategies, including the enrichment of deadwood from native and with a specific focus on locally rare or silviculturally less important tree species

Decadal effects of landscape-wide enrichment of dead wood on saproxylic organisms in beech forests of different historic management intensity

Aim: European temperate forests have lost dead wood and the associated biodiversity owing to intensive management over centuries. Nowadays, some of these forests are being restored by enrichment with dead wood, but mostly only at stand scales. Here, we investigated effects of a seminal dead-wood enrichment strategy on saproxylic organisms at the landscape scale. Location: Temperate European beech forest in southern Germany. Methods: In a before-after control-impact design, we compared assemblages and gamma diversities of saproxylic organisms in strictly protected old-growth forest areas (reserves) and historically moderately and intensively managed forest areas before and a decade after starting a landscape-wide strategy of dead-wood enrichment. Results: Before enrichment with dead wood, the gamma diversity of saproxylic organisms in historically intensively managed forest stands was significantly lower than in reserves and historically moderately managed forest stands; this difference disappeared after 10 years of dead-wood enrichment. The species composition of beetles in forest stands of the three historical management intensities differed before the enrichment strategy, but a decade thereafter, the species compositions of previously intensively logged and forest reserve plots were similar. However, the differences in fungal species composition between historical management categories before and after 10 years of enrichment persisted. Main conclusions: Our results demonstrate that intentional enrichment of dead wood at the landscape scale is a powerful tool for rapidly restoring saproxylic beetle communities and for restoring wood-inhabiting fungal communities, which need longer than a decade for complete restoration. We propose that a strategy of area-wide active restoration combined with some permanent strict refuges is a promising means of promoting the biodiversity of age-long intensively managed Central European beech forests

Locations of flight-interception traps within our study area in salvage-logged (A) and non-salvage-logged windthrows, sampled from 2008 to 2011 (B).

<p>Locations of flight-interception traps within our study area in salvage-logged (A) and non-salvage-logged windthrows, sampled from 2008 to 2011 (B).</p