Mapping of the Xylobionte fauna in dead wood stocks in Gesäuse National Park

The objectives of the research project are the collection of beetle and bedbug species colonising wood in the Gesäuse National Park, the presentation of species diversity depending on, among others, forest type, altitude, exposure and dead wood richness, the identification of particularly valuable forest habitats and, if necessary, the formulation of measures to increase biodiversity in the forest. Beetles were collected in June/July 2016 at 30 locations with the help of approach traps and bark bugs were collected by hand in 2017 at 42 locations. In addition, the bedbugs of the approach traps were also evaluated, which is why bedbug data are available for 53 locations. Data from the FFH habitat type map of the national park and the forest inventory of the national park were included in the data evaluations. A total of 1,553 individual beetles have been collected, which are 231 species from 52 families. 179 species are xylobiont. Among them are 65 freshwood and 62 old wood colonists, 28 species of tree fungus living beetle species, 2 mulm cave colonisers and one species with special biology The species set includes several faunistic and natural biologically remarkable species: among others, Symbiotes armatus (1. Proof of Stmk), Zilora obscura, Cacotemnus thomsoni (both 2. Evidence Stmk), Microrhagus lepidus (3. Evidence of Stmk), Wanachia trigutata, Peltis grossa and Ostoma ferruginea. Also outstanding is the only second Styrian find of the very rare jungle relic species Lacon lepidopterus. Species numbers per location vary greatly. On average, 15-30 species were found per site, the maximum value is reached with 39 species at the Scheichkogel site. The most species-rich locations are located on the one hand at southern, foliage-dominated locations north of the Enns and on the other hand in the east of the national park on higher forest areas. Particularly species-rich forest types are spruce-tap-beech forests, relatively low-species were the investigated snow heath pine forests and the subalpine spruce forests. The evaluation of the beetle communities showed the highest level of value for four locations: Schagermauer, Gstatterstein, E Wirtsalm and E Sulzkarsee. The conservation value increases with the total dead wood volume and the volume of standing dead wood. For the national preservation of a number of extremely rare xylobionate species (e.g. Lacon lepidopterus), the National Park probably has a special responsibility. Bark bugs were detected at 40 of the 53 sites examined. In total, there are eight species. Several species occur in the national park only from a certain stage of forest development and the available deadwood qualities. The presence of dead wood in a stronger dimension and in the advanced phases of decay is crucial. As a by-catch, the Styrian first detection of the extremely rare primeval relic species Cixidia lapponica (Nordic Rindenzikade) in Central Europe was also achieved. For four xylobionte species of long-term ecology of value-determining beetles, occurrence probabilities in the National Park were modeled extensively: Hylecoetus dermestoides (Lymexylonidae; Fresh wood colonisers), melanotus castanipes (Elateridae; Waste wood colonisers), Litargus connexus (Mycetophagidae; Tree mushroom colonisers) and Dolotarsus lividus (Melandryidae; Species of jungle relic). The sum-up of the occurrence probabilities of these representatives of typical xylobionte guilds (beetles, bedbugs) provides evidence of the most valuable forest habitats in the national park for forest biodiversity. The study shows that valuing beetle and bark bug species occur in the national park only from a certain stage of forest development. The presence of dead wood in a stronger dimension (30 cm in diameter) is crucial. High abundances were observed by us on sites with a dead wood supply of more than 70 m/ha, which is about three times the average deadwood stock in the Austrian forest.