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Feuchtwangen, Germany

Muller J.,Bavarian Forest National Park | Muller J.,TU Munich | Bussler H.,Am Greifenkeller 1b
Journal of Insect Conservation | Year: 2013

Natural landscapes characterized by heavy disturbance regimes were displaced in Europe by managed cultural landscapes over the past centuries. The associated loss of biological legacies, such as dead or dying trees, has exposed numerous saproxylic species to high risks of extinction. In contrast, extensive wilderness forests in Northern Mongolia have been sustained owing to significant cultural differences. Here we used saproxylic beetle abundance data gathered during two sampling campaigns in the Mongolian taiga to address whether (1) the saproxylic beetle fauna of the Mongolian taiga is comparable to that of European boreal forests, (2) fires are a natural disturbance regime, indicated by the occurrence of many pyrophilous species, and (3) species rare in Europe are also rare in the Northern Mongolian wilderness. Of 191 saproxylic beetle species identified, 150 (79 %) were also found in Europe. The high number of pyrophilous beetle species (20) indicated that natural species communities are well adapted to this disturbance regime. The species rarity in Germany was significantly positively correlated with the species rarity in Finland, but the species rarity in these two countries was negatively correlated with that in the Mongolian wilderness. Our results indicated that wilderness areas with natural disturbances provide biological legacies important for rare species. Therefore, exploitation of the unique, remaining natural landscapes of the Palaearctic wilderness areas should be stopped. Moreover, we urge conservationists to expand controlled burning for restoration at relict sites of rare boreal species also outside Fennoscandia. © 2013 Springer Science+Business Media Dordrecht. Source

Thorn S.,Bavarian Forest National Park | Thorn S.,TU Munich | Bassler C.,Bavarian Forest National Park | Bussler H.,Am Greifenkeller 1b | And 7 more authors.
Forest Ecology and Management | Year: 2016

The simultaneous control of insect pests and compliance of conservation targets in conifer-dominated forests has intensified public debate about adequate post-disturbance management, particularly in protected areas. Hence, mechanical bark treatments, such as debarking, of disturbance-affected trees have been widely promoted as an on-site method of pest control that accounts for conservation targets because woody biomass is retained. However, the effects of debarking to non-target biodiversity remain unclear. We analyzed data from a two-and-a-half-year field survey of wood-inhabiting fungi, saproxylic beetles and parasitoid wasps in twelve artificial windthrows, created by pulling down mature Norway spruce trees (Picea abies) with winches. Each experimental windthrow comprising one control tree, one completely debarked tree and one bark-scratched tree. Insects were sampled using stem emergence traps. Fruiting bodies of wood-inhabiting fungi, number of wood wasp emergence holes, and number of holes made by foraging woodpeckers were assessed by visual counts. We recorded the amount of time needed to complete debarking by machine, bark-scratching by machine and bark-scratching by chainsaw each on 15 separate trees to estimate the economic costs of mechanical bark treatments. Our results revealed that both debarking and bark-scratching significantly decreased numbers of the emerging target pest Ips typographus to in median 4% (debarked) and 11% (scratched bark) of the number of individuals emerging from untreated control trees. Compared to control trees, debarking significantly reduced the species density of wood-inhabiting fungi, saproxylic beetles, and parasitoid wasps. By contrast, bark-scratching did not reduce the overall species density of wood-inhabiting fungi, saproxylic beetles or parasitoid wasps. The time needed for bark-scratching by machine was significantly lower than debarking, whereas bark-scratching by chainsaw needed a similar amount of time as conventional debarking. However, bark-scratching did have some negative effects in common with debarking, such as the significant reduction of wood wasps emergence holes and the reduction of holes made by foraging woodpeckers. Hence, bark-scratching of downed trees, like debarking, might affect higher trophic levels of biodiversity and should be applied only if pest management is urgently needed. We urge policy makers and natural resource managers to rapidly shift current pest management toward new techniques of bark-scratching, particularly in protected areas. Such a shift in post-disturbance pest-control will foster ecosystem integrity at lower economic cost compared to debarking. © 2015. Source

Muller J.,Bavarian Forest National Park | Muller J.,TU Munich | Bussler H.,Am Greifenkeller 1b | Gossner M.M.,TU Munich
Animal Conservation | Year: 2014

The general importance of dead wood in European beech forests for species requiring high amounts of decayed wood of large diameter has recently been demonstrated using a functional approach. However, the effect of veteran trees, particularly of living hollow trees with mould, on functional diversity, is less understood. These trees are known to be a habitat for a few endangered and specialized arthropods and epiphytes. Their ecological role as a complex habitat has been assumed, but not yet formally tested. We compared the richness and functional and phylogenetic diversity of saproxylic beetle assemblages of vital beech trees, habitat trees (i.e. trees with partial bark loss, broken crowns or sporocarps) and hollow trees with mould. As expected, the richness of red-listed species increased from vital trees to habitat trees to hollow trees. When we controlled for species richness using null models, both functional and phylogenetic diversity were higher for hollow trees than for habitat trees, which can be explained by the habitat heterogeneity hypothesis. Single-trait analyses revealed that hollow trees promoted species requiring late decay stages, large diameters and shady habitats. This suggests that in beech forests, hollow trees not only promote the few specialists of hollow trees, but also play a superior role for species under pressure by current logging practices and as a keystone structure with high habitat diversity at one tree. We therefore urge forest managers and conservationists to monitor particularly the easy-to-identify hollow trees and the conspicuous species living in such trees, as useful umbrellas for a high-diversity dead-wood habitat. © 2013 The Zoological Society of London. Source

Muller J.,Bavarian Forest National Park | Muller J.,TU Munich | Brunet J.,Swedish University of Agricultural Sciences | Brin A.,Purpan Engineering School | And 8 more authors.
Insect Conservation and Diversity | Year: 2013

1.European Beech (Fagus sylvatica) is the natural dominant tree species in many forests across Europe. Despite Europe's global responsibility for these forests, the correct conservation strategies are still a matter of debate. In particular, it remains controversial whether high conservation efforts should be directed towards beech forests, owing to the small number of insects that are Fagus specialists, and at what spatial scale conservation should take place. 2.To provide evidence for this discussion, we compiled saproxylic beetle data from 1115 flight-interception traps in eight countries and addressed two main questions: (i) what percentage of central European species can be expected in beech-dominated forests? and (ii) which are the important spatial scales for the conservation of biodiversity in beech-dominated forests? 3.We included six spatial scales in our analysis: among traps, forest stands, forest sites, low/high elevations, oligo/eutrophic soils, and European bioregions. 4.By extrapolating species numbers, we showed that 70% of the central European saproxylic beetle species can be expected in beech-dominated forests. Multiplicative β-diversity partitioning revealed the forest site level as the most important diversity scale for species richness, particularly for red-listed and rare species, followed by elevation and bioregion. 5.We conclude that beech-dominated forests form a useful umbrella for the high species diversity of central European saproxylic beetles. Conservation activities, such as protecting areas or increasing dead wood, should be undertaken in as many forest sites as possible, at different elevations, and in different bioregions. For this, the Natura 2000 net may provide the most useful template. © 2012 The Royal Entomological Society. Source

Bussler H.,Am Greifenkeller 1b | Bouget C.,IRSTEA | Brustel H.,Purpan Engineering School | Brandle M.,University of Marburg | And 3 more authors.
Forest Ecology and Management | Year: 2011

Scolytids have been studied more than any other group of forest insects, but most investigations have been restricted to only a few pest species. This bias hampers our understanding of variation in abundance and pest status. Even the simple question whether the abundance of scolytids can predicted by the same independent variables as their pest status is still a matter of debate. To explore this issue, we estimated their abundance using non-attracting flight-interception traps set in a wide range of forests across Czech Republic, Germany, and France. Pest status was taken from current literature. As independent variables, we considered host range, host abundance, and several traits of the considered species in linear models using generalized least squares with a correlation structure derived from the phylogenetic tree of the beetles. Host range was calculated as the root phylogenetic diversity index. The variation in the abundance across scolytids was well explained by resource-related parameters (R 2=0.53). In contrast to abundance, the pest status was significantly related to species-specific traits, such as body size and maximum number of generations. However, the explained variance was much lower (R 2=0.19). Although our analysis showed that abundance and pest score follow different patterns, we stress the importance of monitoring all species using non-selective traps. Considering the increasing global trade and the rapidly changing climate, such a broad ecological monitoring is necessary to detect new interactions and/or invading species that may influence our forests ecosystems. © 2011 Elsevier B.V. Source

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