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„The forgotten kingdom“ im Naturschutz
Abstract
Zusammenfassung
Pilze sind sehr artenreich und spielen eine zentrale Rolle im Stoffhaushalt unserer Waldökosysteme. Durch intensive forstliche Nutzung sind heute viele Arten aus unseren Wäldern verschwunden oder hochgradig bedroht. Im Vergleich zu andere Artengruppen spielen Pilze heute immer noch eine untergeordnete Rolle im Naturschutz. Die Forschungsergebnisse des Nationalparks Bayerischer Wald zeigen, dass sich seltene holzbewohnende Pilzarten und Artengemeinschaften nach Einstellung forstlicher Nutzung wieder erholen können. Es gibt eine Reihe von Arten, die heute deutschlandweit ihren Schwerpunkt in den Zonen ohne Nutzung haben. Zum Erhalt der gesamten holzbewohnenden Pilzdiversität in Deutschland müssten aber auch die Eigentümer von Wirtschaftswäldern ihrer Verantwortung gerecht werden. Hierzu gehören der Erhalt und die Förderung von alten Bäumen (Habitatbäume) sowie die künstliche Schaffung spezifischer Totholzstrukturen. Weiterhin sollten Konzepte zur Wiederansiedelung lokal ausgestorbener Arten entwickelt werden.
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Dead wood is a habitat for numerous fungal species, many of which are important agents of decomposition. Previous studies suggested that wood‐inhabiting fungal communities are affected by climate, availability of dead wood in the surrounding landscape and characteristics of the colonized dead‐wood object (e.g. host tree species). These findings indicate that different filters structure fungal communities at different scales, but how these factors individually drive fungal fruiting diversity on dead‐wood objects is unknown.
We conducted an orthogonal experiment comprising 180 plots (0.1 ha) in a random block design and measured fungal fruit body richness and community composition on 720 dead‐wood objects over the first 4 years of succession. The experiment allowed us to disentangle the effects of the host (beech and fir; logs and branches) and the environment (microclimate: sunny and shady plots; local dead wood: amount and heterogeneity of dead wood added to plot).
Variance partitioning revealed that the host was more important than the environment for the diversity of wood‐inhabiting fungi. A more detailed model revealed that host tree species had the highest independent effect on richness and community composition of fruiting species of fungi. Host size had significant but low independent effects on richness and community composition of fruiting species. Canopy openness significantly affected the community composition of fruiting species. By contrast, neither local amount nor heterogeneity of dead wood significantly affected the fungal diversity measures.
Synthesis . Our study identified host tree species as a more important driver of the diversity of wood‐inhabiting fungi than the environment, which suggests a host‐centred filter of this diversity in the early phase of the decomposition process. For the conservation of wood‐inhabiting fungi, a high variety of host species in various microclimates is more important than the availability of dead wood at the stand level.
Summary
To evaluate forests from a nature conservation point-of-view different kind of parameter or indicators could be used. To valuate the quality of dead wood as one of the main structural parameters of forest-ecosystems it is often not enough to estimate the volume.
By consulting experts and carry out a literature survey, a list of 68 wood-inhabiting fungi was composed as indicators. This list allowed a better valuation of dead wood quality and quantity in forests. This fungi could be used as indicators of the orientation by nature. Other six species of fungi could be use as indicator for native structure elements in connection with their abundance.
Zusammenfassung
Zur naturschutzfachlichen Einwertung Einstufung von Waldbeständen können verschiedene Parameter bzw. Indikatoren verwendet werden. Die Erfassung rein numerischer Totholzmengen reicht häufig für die Bewertung der Totholzqualität als wesentlicher Struktur in Waldökosystemen nicht aus. Zu diesem Zweck wurde auf der Grundlage einer Expertenbefragung und Literaturstudien ein Liste von 68 holzbewohnenden Pilzen zusammengestellt, die eine bessere Bewertung der Totholzqualität und –quantität in Wäldern zulassen und somit ein Weiser für die Naturnähe von Waldbeständen sein können. Weitere sechs Arten sind in Verbindung mit Abundanzangaben ebenfalls Indikatorarten für naturnahe Strukturen.
Fungi play key roles in ecosystems as mutualists, pathogens, and decomposers. Current estimates of global species richness are highly uncertain, and the importance of stochastic vs. deterministic forces in the assembly of fungal communities is unknown. Molecular studies have so far failed to reach saturated, comprehensive estimates of fungal diversity. To obtain a more accurate estimate of global fungal diversity, we used a direct molecular approach to census diversity in a boreal ecosystem with precisely known plant diversity, and we carefully evaluated adequacy of sampling and accuracy of species delineation. We achieved the first exhaustive enumeration of fungi in soil, recording 1002 taxa in this system. We show that the fungus : plant ratio in Picea mariana forest soils from interior Alaska is at least 17:1 and is regionally stable. A global extrapolation of this ratio would suggest 6 million species of fungi, as opposed to leading estimates ranging from 616 000 to 1.5 million. We also find that closely related fungi often occupy divergent niches. This pattern is seen in fungi spanning all major functional guilds and four phyla, suggesting a major role of deterministic niche partitioning in community assembly. Extinctions and range shifts are reorganizing biodiversity on Earth, yet our results suggest that 98% of fungi remain undescribed and that many of these species occupy unique niches.
To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large-scale extinction processes must be identified. A promising approach is to link the red-list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional-odds linear mixed-effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red-list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad-leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad-leaved forests to dense conifer-dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad-leaved trees, and dead wood in sunny areas.
Hitherto fungi have rarely been considered in conservation biology, but this is changing as the field moves from addressing single species issues to an integrative ecosystem‐based approach. The current emphasis on biodiversity as a provider of ecosystem services throws the spotlight on the vast diversity of fungi, their crucial roles in terrestrial ecosystems, and the benefits of considering fungi in concert with animals and plants. We reviewed the role of fungi in ecosystems and composed an overview of the current state of conservation of fungi. There are 5 areas in which fungi can be readily integrated into conservation: as providers of habitats and processes important for other organisms; as indicators of desired or undesired trends in ecosystem functioning; as indicators of habitats of conservation value; as providers of powerful links between human societies and the natural world because of their value as food, medicine, and biotechnological tools; and as sources of novel tools and approaches for conservation of megadiverse organism groups. We hope conservation professionals will value the potential of fungi, engage mycologists in their work, and appreciate the crucial role of fungi in nature.
Una Perspectiva Micótica de la Biología de la Conservación
Rapid destruction of forest habitats has led to the establishment of protected areas in formerly managed forests with the aim of restoring biodiversity. Conservation in spruce-dominated reserves is often contradicted by salvage logging after insect outbreaks. Here we study the community characteristics of wood decaying fungi in a high montane Norway Spruce forest with three different management types: (1) a formerly managed area disturbed by a large-scale bark beetle outbreak, (2) an area with continuous salvage logging, and (3) an old-growth forest. Bark beetle activity in the disturbed area resulted in downed wood amounts comparable to those of the old-growth forest. However, species accumulation curves for the disturbed forest were more similar to those of the logged forest than to those of the old-growth forest. This arose because of differences in the diversity of wood decay classes; wood decay in the disturbed forest was more homogeneous. Logs in the disturbed forest originated almost exclusively from bark-beetle-infested trees, but the causes of tree mortality in the old-growth forest were manifold. Although most red-listed species were clearly confined to old-growth forest, Antrodiella citrinella was most abundant in the disturbed forest. Our analysis furthermore showed that the between stand scale is the most effective unit for diversity wood-decaying fungi. We therefore suggest a conservation strategy for preserving old-growth forests and establishing protected forest stands to enhance structural heterogeneity in spruce-dominated forests. For this, a careful screening of protected areas throughout Europe is necessary to provide managers with guidelines for conservation.
In contemporary forest management, also of commercial forests, threshold values are widely used for consideration of biodiversity
conservation. Here, we present various aspects of dead-wood threshold values. We review published and unpublished dead-wood
threshold data from European lowland beech–oak, mixed-montane, and boreo-alpine spruce–pine forests separately to provide
managers of European forests with a baseline for management decisions for their specific forest type. Our review of dead-wood
threshold data from European forests revealed 36 critical values with ranges of 10–80m3ha−1 for boreal and lowland forests and 10–150m3ha−1 for mixed-montane forests, with peak values at 20–30m3ha−1 for boreal coniferous forests, 30–40m3ha−1 for mixed-montane forests, and 30–50m3ha−1 for lowland oak–beech forests. We then expand the focus of dead-wood threshold analyses to community composition. We exemplify
the two major statistical methods applied in ecological threshold analysis to stimulate forest researchers to analyze more
of their own data with a focus on thresholds. Finally, we discuss further directions of dead-wood threshold analysis. We anticipate
that further investigations of threshold values will provide a more comprehensive picture of critical ranges for dead wood,
which is urgently needed for an ecological and sustainable forestry.
KeywordsThresholds-Conditional inference tree-Maximally selected rank statistic-Logistic regression-Bootstrapping-Variable selection
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 64 m3 ha−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 ≈15 m3 ha−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.
Data were analysed on the volume of dead wood in 86 beech forest reserves, covering most of the range of European beech forests. The mean volume was 130 m3/ha and the variation among reserves was high, ranging from almost nil to 550 m3/ha. The volume depended significantly on forest type, age since reserve establishment and volume of living wood. More dead wood was found in montane (rather than lowland/submontane) reserves, longer-established reserves (time since designation) and reserves with higher volumes of living wood.On average, fallen dead wood contributed more to the total dead wood volume than standing dead wood. The percentage of dead wood that was standing was almost twice as high in montane than in lowland/submontane forest reserves (45% versus 25%). The volume of dead wood at selected sites changed considerably over time. The fluctuations were significantly higher in lowland/submontane than montane reserves, possibly connected with differences in the disturbance regimes and especially damage caused by windstorms. In NW Europe, the blow down of formerly managed, even-aged stands led to extraordinary high volumes of dead wood shortly after reserve establishment.The implications for forest management and biodiversity conservation are discussed. An increase in dead wood volumes must be carried out in accordance with the local/regional forest type and disturbance regime. Thus, in order to fulfil the requirements of as many wood-depending organisms as possible, it is important to preserve not only larger amounts of dead wood, but also dead wood of different types and dimensions as well as securing a long-term continuity of dead wood.
Biome-scaledisturbancesbyeruptiveherbivoresprovidevaluableinsightsintospeciesinteractions,ecosystemfunction,andimpactsof globalchange. We present a conceptual framework using one system as a model, emphasizing interactions across levels of biological hierarchy and spatiotemporal scales. Bark beetles are major natural disturbance agents in western North American forests. However, recent bark beetle population eruptions have exceeded the frequencies, impacts, and ranges documented during the previous 125 years. Extensive host abundance and susceptibility, concentrated beetle density, favorable weather, optimal symbiotic associations, and escape from natural enemies must occur jointly for beetles to surpass a series of thresholds and exert widespread disturbance. Opposing feedbacks determine qualitatively distinct outcomes at junctures at the biochemical through landscape levels. Eruptions occur when key thresholds are surpassed, prior constraints cease to exert influence, and positive feedbacks amplify across scales. These dynamics are bidirectional, as landscape features influence how lower-scale processes are amplified or buffered. Climate change and reduced habitat heterogeneity increase the likelihood that key thresholds will be exceeded, and may cause fundamental regime shifts. Systems in which endogenous feedbacks can dominate after external forces foster the initial breach of thresholds appear particularly sensitive to anthropogenic perturbations.
Throughout the world, efforts are under way to restore watersheds, but restoration planning rarely accounts for future climate change. Using a series of linked models of climate, land cover, hydrology, and salmon population dynamics, we investigated the impacts of climate change on the effectiveness of proposed habitat restoration efforts designed to recover depleted Chinook salmon populations in a Pacific Northwest river basin. Model results indicate a large negative impact of climate change on freshwater salmon habitat. Habitat restoration and protection can help to mitigate these effects and may allow populations to increase in the face of climate change. The habitat deterioration associated with climate change will, however, make salmon recovery targets much more difficult to attain. Because the negative impacts of climate change in this basin are projected to be most pronounced in relatively pristine, high-elevation streams where little restoration is possible, climate change and habitat restoration together are likely to cause a spatial shift in salmon abundance. River basins that span the current snow line appear especially vulnerable to climate change, and salmon recovery plans that enhance lower-elevation habitats are likely to be more successful over the next 50 years than those that target the higher-elevation basins likely to experience the greatest snow–rain transition.
• Chinook salmon
• hydrologic model
• population model
• Snohomish River
• stream flow
Limited knowledge of dispersal for most organisms hampers effective connectivity conservation in fragmented landscapes. In forest ecosystems, deadwood-dependent organisms (i.e., saproxylics) are negatively affected by forest management and degradation globally. We reviewed empirically established dispersal ecology of saproxylic insects and fungi. We focused on direct studies (e.g., mark-recapture, radiotelemetry), field experiments, and population genetic analyses. We found 2 somewhat opposite results. Based on direct methods and experiments, dispersal is limited to within a few kilometers, whereas genetic studies showed little genetic structure over tens of kilometers, which indicates long-distance dispersal. The extent of direct dispersal studies and field experiments was small and thus these studies could not have detected long-distance dispersal. Particularly for fungi, more studies at management-relevant scales (1-10 km) are needed. Genetic researchers used outdated markers, investigated few loci, and faced the inherent difficulties of inferring dispersal from genetic population structure. Although there were systematic and species-specific differences in dispersal ability (fungi are better dispersers than insects), it seems that for both groups colonization and establishment, not dispersal per se, are limiting their occurrence at management-relevant scales. Because most studies were on forest landscapes in Europe, particularly the boreal region, more data are needed from nonforested landscapes in which fragmentation effects are likely to be more pronounced. Given the potential for long-distance dispersal and the logical necessity of habitat area being a more fundamental landscape attribute than the spatial arrangement of habitat patches (i.e., connectivity sensu strict), retaining high-quality deadwood habitat is more important for saproxylic insects and fungi than explicit connectivity conservation in many cases.
Commercial forestry increasingly aims at both optimizing timber production and maintaining species
diversity. To maintain the diversity of the species-rich group of wood-inhabiting fungi, effective forest
conservation concepts that include the enrichment of dead wood in commercial forests are required.
However, which type of dead wood should be enriched in which type of forest stand (coniferous or
broad-leaved) is still debated. Our study aimed at (1) disentangling the relative importance of forest-
stand type, dead-wood origin (tree species) and time since death and (2) determining whether fungal
species richness on logs of broad-leaved trees is higher in broad-leaved stands than in coniferous
stands and whether fungal species richness on logs of coniferous trees is higher in coniferous stands
than in broad-leaved stands (home-field advantage). We exposed logs of 9 broad-leaved and 4 conif-
erous tree species in 19 broad-leaved and 9 coniferous forest stands in 2009 and surveyed the logs in
2012 and 2014 for wood-inhabiting fungi. Across all logs, fungal species richness was mainly driven
by the tree species of the dead wood and time since death, whereas fungal community composition
was solely driven by the tree species of the dead wood. The fungal species richness and community
composition of broad-leaved logs was significantly correlated to time since death but not to forest-
stand type. The fungal species richness and community composition of coniferous logs was neither
affected by forest-stand type nor time since death. When individual tree species were considered,
forest-stand type did not affect fungal species richness or community compositions, but fungal species
richness on logs of Acer, Fagus, Carpinus and Populus increased with time since death. To increase the
species richness of wood-inhabiting fungi in commercial forests, we recommend that the tree species
diversity of dead wood should be increased and should especially originate from different lineages
(angiosperms and gymnosperms), and that a broad variety of successional stages of dead wood should
be maintained. Our results suggest that such a strategy would be effective irrespective of the tree
species composition of the forest stand, as we found no support for home-field advantages in the
early stage of decomposition.
Saproxylic insects comprise a diverse, species-rich and dominant functional group that share a dependence on dead wood and the old trees that generate it (mature timber habitat). Recent research has highlighted their sensitivity to forest management, with managed or secondary forests generally supporting fewer individuals, fewer species, and different assemblages compared to old-growth or primary forests. This sensitivity is a product of their association with a habitat that tends to diminish in managed forests. Many species also have low powers of dispersal relative to human-induced fragmentation, making breaks in habitat continuity particularly harmful. In western Europe, many species are now regionally extinct. Information is largely lacking elsewhere, but similar ecological and management principles should apply. Measures taken to protect the habitat of hollow-dependent vertebrates may ensure the survival of some saproxylic insects, but unless their needs are expressly considered, there remains the risk that many others may be lost as forest areas shrink and management of remaining areas intensifies.
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.
Fossils document the existence of trees and wood-associated organisms from almost 400 million years ago, and today there are between 400,000 and 1 million wood-inhabiting species in the world. This is the first book to synthesise the natural history and conservation needs of wood-inhabiting organisms. Presenting a thorough introduction to biodiversity in decaying wood, the book studies the rich diversity of fungi, insects and vertebrates that depend upon dead wood. It describes the functional diversity of these organisms and their specific habitat requirements in terms of host trees, decay phases, tree dimensions, microhabitats and the surrounding environment. Recognising the threats posed by timber extraction and forest management, the authors also present management options for protecting and maintaining the diversity of these species in forests as well as in agricultural landscapes and urban parks.
The lack of management experience at the landscape scale and the limited feasibility of experiments at this scale have increased the use of scenario modeling to analyze the effects of different management actions on focal species. However, current modeling approaches are poorly suited for the analysis of viability in dynamic landscapes. Demographic (e.g., metapopulation) models of species living in these landscapes do not incorporate the variability in spatial patterns of early successional habitats, and landscape models have not been linked to population viability models. We link a landscape model to a metapopulation model and demonstrate the use of this model by analyzing the effect of forest management options on the viability of the Sharp-tailed Grouse ( Tympanuchus phasianellus) in the Pine Barrens region of northwestern Wisconsin (U.S.A.). This approach allows viability analysis based on landscape dynamics brought about by processes such as succession, disturbances, and silviculture. The landscape component of the model (LANDIS) predicts forest landscape dynamics in the form of a time series of raster maps. We combined these maps into a time series of patch structures, which formed the dynamic spatial structure of the metapopulation component (RAMAS). Our results showed that the viability of Sharp-tailed Grouse was sensitive to landscape dynamics and demographic variables such as fecundity and mortality. Ignoring the landscape dynamics gave overly optimistic results, and results based only on landscape dynamics (ignoring demography) lead to a different ranking of the management options than the ranking based on the more realistic model incorporating both landscape and demographic dynamics. Thus, models of species in dynamic landscapes must consider habitat and population dynamics simultaneously.
As the E arth's biota enters the sixth great mass extinction event recorded in the history of the planet, it is predicted that the erosion of biodiversity will result in the reduction of the goods and services that ecosystems provide. To mediate the loss of biodiversity and ecosystem function associated with wood production in temperate forests in E urope, a near‐to‐nature strategy has been developed. Whether this strategy enables natural assembly mechanisms of fungi responsible for major ecosystem processes is unknown.
We analysed variation in species richness and both the functional and phylogenetic structure of fungal assemblages of different trophic life histories (soil saprotrophic, wood saprotrophic, and ectomycorrhizal fungi) in 69 beech forest plots along a steep gradient of management intensity. We focused on reproductive traits to test the hypothesis that management intensity shifts community assembly mechanisms from limitations in niche overlap that promote the coexistence of dissimilar species to environmental filtering that selects for similar species. Specifically, we hypothesized that unpredictable resources in production forests filter the assemblages, promoting species with small fruit bodies and with small and elongated spores.
As management intensity increased, functional diversity decreased from a random pattern to a clustered pattern, which indicated that management intensity increased the strength of environmental filtering. However, phylogenetic diversity increased from a random pattern to an overdispersed pattern. Combining phylogenetic diversity with functional diversity did not provide additional insight into the traits but revealed a contrasting pattern. Reproduction traits of the assemblages shifted, with a decrease in mean fruit body size and an increase in spore elongation.
Synthesis and applications . Near‐to‐nature logging concepts are not able to mimic the major processes that shape fungal community assembly in protected forests. This could have severe consequences for important ecosystem functions provided by fungi. The phylogenetic overdispersion indicated that analyses of other traits in addition to reproductive traits are required to disentangle the factors affecting fungal community structure.
A conservative estimate for the total number of species dependent on dead-wood habitats is 4000-5000 within the area of Finland, which accounts for 20-25% of all forest-dwelling species. A large body of data concerning the average amounts of coarse woody debris (CWD) in both natural and managed forests has accumulated during the 1990s in Fennoscandia, including results from national forest inventories. The average volume of CWD in old-growth forests is generally 60-90 m³ $\text{ha}^{-1}$ in southern Fennoscandia, and declines to 20 m³ $\text{ha}^{-1}$ close to the timberline. Available data and modelling results indicate that the volume is even much higher following disturbance, and only slightly lower in mature natural forests. In managed forest landscapes the average volumes vary between 2 and 10 m³ $\text{ha}^{-1}$ depending on the region. This means that the average amount of CWD at the landscape level has probably been reduced by 90-98%. General species-area relationships suggest that such a reduction in available habitat might lead to the disappearance of > 50% of original saproxylic species in managed forests in the long term. Several recent studies have shown that the number of saproxylic species per stand depends on the amount of CWD, and also on the average size and decay stage of dead trunks. These relationships can be explained by either higher habitat diversity (more different niches) or larger population sizes of individual species (lower risk for local extinction) with increasing amount of CWD. A third important factor explaining local species richness of species living in ephemeral habitat patches, i.e. dead trees that decay away, is the spatiotemporal continuity of suitable host trees. Important theoretical and practical issues for conservation, management and research include, for instance, how well the remaining high-quality patches (e.g. old-growth fragments, key habitats) can secure the regional persistence of saproxylic species, and how much, what kind, and where CWD should be retained in the ordinary managed forests in order to maintain most of the species.
Evolutionary relations are better represented by new classifications than by the traditional two kingdoms.
Abstract Saproxylic insects comprise a diverse, species-rich and dominant functional group that share a dependence on dead wood and the old trees that generate it (mature timber habitat). Recent research has highlighted their sensitivity to forest management, with managed or secondary forests generally supporting fewer individuals, fewer species, and different assemblages compared to old-growth or primary forests. This sensitivity is a product of their association with a habitat that tends to diminish in managed forests. Many species also have low powers of dispersal relative to human-induced fragmentation, making breaks in habitat continuity particularly harmful. In western Europe, many species are now regionally extinct. Information is largely lacking elsewhere, but similar ecological and management principles should apply. Measures taken to protect the habitat of hollow-dependent vertebrates may ensure the survival of some saproxylic insects, but unless their needs are expressly considered, there remains the risk that many others may be lost as forest areas shrink and management of remaining areas intensifies.
1. Wood-decaying fungi are crucial for the functioning of forest ecosystems. We tested the hypotheses that on coarse woody debris (CWD), the abundance, diversity and composition of fungi depend more on the amount of available resource than on macro- or microclimate, and that on fine woody debris (FWD) more on the microclimate because of the rapid desiccation of thin woody debris.
2. We sampled 7183 dead wood objects with 10 818 fungal samples on 290 plots along four transects, from 650 to 1450 m a.s.l., in the Bavarian Forest National Park, Germany, Overall, we recorded 263 species (54 only on FWD and 71 only on CWD).
3. For each plot, we characterized the macroclimate using field data and a terrain model. Microclimate variables were extracted from remote-sensing and ground surveys. Resource availability was characterized by measuring the amount, tree species composition, diameter and rotting stage of all dead wood objects. We extracted principal components from each of the three data sets for further analyses.
4. The number of species found per sampled surface area of woody debris indicated that the fungal community on FWD needs a much lower surface area than that on CWD; FWD probably provides more niches per unit surface area than CWD. The abundance of fungi (and therefore also species density) living on FWD and CWD as well as the fungal community composition on CWD were clearly driven by variables characterizing the amount and diversity of the resource. In general, the surface area was the most important factor for abundance of species. In contrast, the community composition on FWD was better predicted by variables characterizing the microclimate.
5. Synthesis. Our results supported the hypotheses that the amount of available resources is more important than macroclimate for fungi living on CWD, and microclimate is more important for fungi living on FWD. Therefore, both dead wood removal and silviculture, which, like logging, open the canopy and increases sunlight exposure, will strongly affect the diversity of wood-decaying fungi in forests. For the conservation of this important group of organisms in forests, silvicultural strategies are more important than climate.
Eleven Norway spruce Picea abies (L.) Karst. forests in the boreal zone of Sweden were studied to investigate the effects of selective cuttings on wood-inhabiting fungi from the families Polyporaceae, Hymenochaetaceae and Corticiaceae (Basidiomycota). The 11 sites constitute a gradient from extensively logged to semi-natural forests. Old selective loggings that occurred about 100 years ago have significantly decreased the availability of large and highly decayed logs. Based on fruit bodies, both the total species number as well as the number of threatened species decreased with increasing degree of cutting.Some of the occurring wood-inhabiting fungi are commonly accepted as indicator species of forests with old-growth conditions. These species showed pronounced preferences for well decayed and large logs. They were also more frequent in the less affected sites and became rarer with increasing degree of cutting; they therefore seem to be good indicators of forests less affected by logging.
Global conventions on biological diversity force governments to develop region-wide conservation strategies. Such strategies are difficult to design for all taxa because little is known about the important spatial scales. Here we applied additive partitioning of the diversity of saproxylic beetles in Bavarian forests in Southern Germany using a nested hierarchical design of five increasingly broader spatial levels: trap, strata, forest stand, forest site, and ecoregion. We consistently found a significantly higher percentage than expected by chance of between ecoregion diversity and significantly lower α diversity within traps. A significant proportion of β diversity was also found between stands. Analysis of species represented by <0.005% of all specimens in our samples and of species classified as threatened revealed similar results. Critical spatial scales for threatened species encompassed the critical levels of common species. Within habitat substratum guilds, the proportion of β diversity increased from species associated with fresh wood to those associated with rotten wood to those associated with fungi. Our results suggest that the most effective way to ensure saproxylic beetle diversity in a state-wide strategy is to add new conservation sites within different ecoregions and to establish new conservation areas in additional forest stands, rather than to enlarge reserves. Our findings further suggest that monitoring of saproxylic beetle diversity on a broader scale in European temperate forests can be restricted to “monitoring species”, i.e. a subgroup of families easy to identify, and that canopy sampling can be neglected without a substantial loss of information.
Most strictly protected areas world-wide have been established in former commercial forests, but there is little evidence that this strongly advocated tool of conservation has had positive effects on endangered species in the short run of decades. One of the major reasons for the failure of habitat improvement in most of these reserves is a lack of natural disturbance. Consequently, only a few studies of species recovery in protected areas after natural disturbance are available. We demonstrate how natural dynamics in the oldest national park in Germany allows the area-wide recovery of the rare wood-inhabiting fungus Antrodiella citrinella. Our analyses showed that an increase of dead wood at >134-224 m(3)ha(-1), amounts known from primeval forests, allowed the fungus, which has barely survived as 'living dead' in two remnants of pristine forests, to spread from this small relict populations to the whole national park, within a radius of more than 30 km. Our result demonstrate that natural disturbance, even in former commercial forests, allowed the recovery of this rare species and fully supports the use of passive management in protected areas, even if natural dynamics often evokes debates on salvage logging.
Natura 2000 – Management im Nationalpark Bayerischer Wald
- Kiener H.
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- J Battin
Battin, J., et al., Projected impacts of climate change on salmon
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www.biuz.de
6/2018 (48) Biol. Unserer Zeit 381
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