Experimente zu Biodiversität und Ökosystemleistungen
Hier finden Sie englisch- und deutschsprachige Zusammenfassungen von verschiedenen Veröffentlichungen zu Ergebnissen aus dem Teilprojekt 2 - Experimente zu Biodiversität und Ökosystemleistungen.
An experimental test of the habitat - amount hypothesis for saproxylic beetles in a forested region
The habitat-amount hypothesis challenges traditional concepts that explain species richness within habitats, such as the habitat-patch hypothesis, where species number is a function of patch size and patch isolation. It posits that effects of patch size and patch isolation are driven by effects of sample area, and thus that the number of species at a site is basically a function of the total habitat amount surrounding this site. We tested the habitat-amount hypothesis for saproxylic beetles and their habitat of dead wood by using an experiment comprising 190 plots with manipulated patch sizes situated in a forested region with a high variation in habitat amount (i.e., density of dead trees in the surrounding landscape). Although dead wood is a spatio-temporally dynamic habitat, saproxylic insects have life cycles shorter than the time needed for habitat turnover and they closely track their resource. Patch size was manipulated by adding various amounts of downed dead wood to the plots (~800 m³ in total); dead trees in the surrounding landscape (~240 km2) were identified using airborne laser scanning (light detection and ranging). Over 3 yr, 477 saproxylic species (101,416 individuals) were recorded. Considering 20–1,000 m radii around the patches, local landscapes were identified as having a radius of 40–120 m. Both patch size and habitat amount in the local landscapes independently affected species numbers without a significant interaction effect, hence refuting the island effect. Species accumulation curves relative to cumulative patch size were not consistent with either the habitat-patch hypothesis or the habitat-amount hypothesis: several small dead-wood patches held more species than a single large patch with an amount of dead wood equal to the sum of that of the small patches. Our results indicate that conservation of saproxylic beetles in forested regions should primarily focus on increasing the overall amount of dead wood without considering its spatial arrangement. This means dead wood should be added wherever possible including in local landscapes with low or high dead-wood amounts. For species that have disappeared from most forests owing to anthropogenic habitat degradation, this should, however, be complemented by specific conservation measures pursued within their extant distributional ranges.
Autoren: Seibold, S.; Bässler, C.; Brandl, R., Fahrig.; L., Förster, B.; Heurich, M.; Hothorn, T.; Scheipl, F.; Thorn, S. & Müller, J. (2017) in Ecology, 98, 1613–1622.
Small-scale positive response of terrestrial gastropods to dead-wood addition is mediated by canopy openness
Terrestrial gastropods can benefit from coarse woody debris, even though they are not saproxylic because dead wood maintains suitable microclimatic conditions and provides food resources and essential nutrients, e.g. calcium. Effects of dead wood on terrestrial gastropods have been studied mostly for coarse woody debris at intermediate and advanced stages of decomposition. However, it remains unclear whether dead wood at an early stage of decomposition and of small diameter has similar positive effects on terrestrial gastropods and how effects of dead wood are mediated by canopy openness. We experimentally exposed different amounts of fresh coarse and fine woody debris on 190 temperate forest plots with either high or low canopy openness and studied terrestrial gastropod activity three years after. Plots with high canopy openness had dense herb layers. Feeding activity of gastropods was higher close than distant to dead wood. This effect was stronger on shady plots. The amount of both fine and coarse woody debris positively affected the feeding activity of gastropods, but only on shady plots. The effect of coarse woody debris amount might be partly due to increased leaf litter accumulation. Our results indicated that dead wood plays a stronger role for terrestrial gastropods in shady than in sunny forests with a dense herb layer and that terrestrial gastropods benefit from both coarse and fine woody debris already at an early stage of decomposition. Thus, conservation strategies that aim at maintaining biodiversity of saproxylic assemblages by retaining or adding dead wood are also beneficial for gastropods, especially in shady forests.
Autoren: Kirchenbaur, T.; Fartmann, T.; Bässler, C.; Löffler, F.; Müller, J.; Strätz, C. & Seibold, S. (2017) in Forest Ecology and Management, 396, 85-90.
Microclimate and habitat heterogeneity as the major drivers of beetle diversity in dead wood
- 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.
- 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.
- 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 dead-wood 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.
- 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.
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.
Autoren: Seibold, S.; Bässler, C.; Brandl, R.; Büche, B.; Szallies, A.; Thorn, S.; Ulyshen, M. D. & Müller, J. (2016) in Journal of Applied Ecology, 53, 934–943.
Dead-wood addition promotes non-saproxylic epigeal arthropods but effects are mediated by canopy openness
Restoring dead-wood amounts in forests is an increasingly and successfully applied conservation measure to counteract negative effects of intensive logging on biodiversity of saproxylic taxa. By contrast, if and how dead-wood addition benefits the vast number of non-saproxylic forest taxa, and how this varies with contextual factors like canopy openness, remains poorly understood. To enhance dead-wood addition strategies, it is thus important to understand how dead wood affects entire forests communities, not just saproxylic taxa. To untangle effects of dead-wood addition and canopy openness on non-saproxylic epigeal arthropods, we exposed different amounts of logs and branches on 190 0.1-ha plots located in sunny or shady mixed montane forests and sampled epigeal arthropods over three years. Canopy openness was a major driver of species assemblage composition and clearly mediated the effects of dead wood on epigeal beetles, spiders/harvestmen and springtails. Most species groups responded positively to the addition of dead wood. All groups decreased in number with increasing distance to dead wood. Dead wood affected taxa of both lower and higher trophic levels directly and taxa of higher trophic levels benefitted also indirectly owing to bottom-up effects. Our results indicate that increasing the amount of dead wood for conservation of saproxylic taxa benefits also non-saproxylic epigeal arthropods and thus, a larger number of forest species than commonly assumed. Because of the strong effects of canopy openness, similar to those found for saproxylic taxa, dead wood in both sunny and shady forest stands is needed.
Autoren: Seibold, S.; Bässler, C.; Baldrian, P.; Reinhard, L.; Thorn, S.; Ulyshen, M. D.; Weiß, I. & Müller, J. (2016) in Biological Conservation, 204, 181–188.
Wood resource and not fungi attract early-successional saproxylic species of Heteroptera - an experimental approach
- The availability of dead wood and ability to colonise these ephemeral structures are crucial for sustaining vital populations of saproxylic insects. These insects locate suitable resources mostly visually and via olfactory cues emitted by dead wood and/or wood-decaying fungi.
- For the conservation of saproxylic species of Heteroptera, a poorly studied group with a high proportion of threatened species, it is crucial to know which dead-wood structures are needed and how they are detected and colonised.
- In a field experiment, we exposed different amounts of dead-wood logs and branches of the main tree species of montane beech forests (Abies alba, Fagus sylvatica) on sunny and shady forest plots. We sampled saproxylic heteropterans and sporocarps of wood-decaying fungi in two consecutive years to test the hypothesis that early-successional saproxylic heteropterans are more attracted to wood-decaying fungi than to wood itself.
- The activity densities of saproxylic heteropterans measured with flight-interception traps increased with increasing surface of coarse woody debris and was higher under sunny conditions. Tree species, fine woody debris and abundance of sporocarps had no significant effect.
Our results suggest that during the early-successional forest stage, dead wood provides more important cues than fungi in the search of saproxylic heteropterans for suitable hosts despite assumed close associations of the insects and certain fungal species. To improve habitats for saproxylic heteropterans, we recommend increasing the supply of dead wood of large diameter (>30 cm) in montane beech forests, particularly in sunny gaps. This can easily be realised during logging operations by gap felling.
Seibold, S.; Bässler, C.; Baldrian, P.; Thorn, S.; Müller, J. & Gossner, M. M. (2014) in Insect Conservation and Diversity, 7, 533–542.
Lamprodema maura (Fabricius, 1803) - Erstnachweiß für Deutschland aus dem Nationalpark Bayrischer Wald (Heteroptera: Rhyparochromidae, Megalontini)
Lamprodema maura (FABRICIUS, 1803) has been recorded in Germany for the first time. One female was sampled with a flight-interception trap in 1130m a.s.l. in the Bavarian Forest National Park in July 2015. The site does not match the known habitat requirements of the Mediterranean species well. Thus vital populations of this species are not expected to occur at this site. A spread from nearby populations in Austria or the Czech Republic is likely.
Autoren: Gossner, M.; Hagge, J. & Seibold, S. (2017) in NachrBl. bayer. Ent., 66 (3/4), 93-97.
Neue Käfernachweise im Nationalpark Bayrischer Wald im Rahmen von Totholzexperimenten (Insecta, Coleoptera)
Im Rahmen eines Experiments zur Bedeutung von Totholz für die Artenvielfalt wurden im Nationalpark BayerischerWald zwischen 2012 und 2014 1675 Käferarten nachgewiesen, davon 622 Arten neu für den Nationalpark. Die hohe Artenvielfalt (1984 Käferarten), darunter viele Rote-Liste Arten und Urwaldreliktarten, unterstreicht denWert derWälder dieser Region.
Autoren: Seibold, S.; Büche, B.; Szallies, A. & Müller, J. (2017) in Beiträge zur bayrischen Entomofaunistik 17, 1-17.
Besonnung und Totholzvielfalt - zwei ökologische Schlüsselgrößen
Ein großangelegtes Freilandexperiment in der Randzone des Nationalparks Bayerischer Wald hat ergeben, dass die Artenvielfalt von Totholz bewohnenden Käfern vor allem mit der Vielfalt an Totholz und nicht ausschließlich mit der reinen Menge steigt. Daneben fördert Totholz in Sonne und Schatten völlig andere Artengemeinschaften. In dicken Stämmen ist im Lauf der Zersetzung allerdings immer eine besonders hohe Vielfalt an Totholznischen gegeben. Diese Ergebnisse eröffnen Waldbesitzern effiziente Möglichkeiten, die biologische Vielfalt in ihren Wäldern zu fördern.
Autoren: Seibold, S.; Leibl, F. & Müller, J. (2017) in AFZ - Der Wald 3, 25-26.
Eckpfeiler gegen Artenschwund bei Totholzbewohnern
Eine Auswertung der aktuellen Roten Liste der Totholzkäfer Deutschlands erlaubt es, vier bundesweite Eckpfeiler für eine Verbesserung unserer Wälder in Bezug auf Naturschutz zu setzen. Gleichzeitig spiegeln die Ergebnisse wider, dass das heutige Aussterberisiko dieser Artengruppe eng mit der modernen Forstwirtschaft seit Ende des 18. Jh. verbunden ist.
Autoren: Seibold, S. & Leibl, F. (2015) in AFZ - Der Wald 8, 23-24.