Article

Animal diversity in beech forests – An analysis of 30 years of intense faunistic research in Hessian strict forest reserves

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Abstract

Under natural conditions beech forest would be the most widespread habitat in Central Europe. Therefore the knowledge of this vegetation type, including the animal communities dwelling there, as well as the mechanisms forming these communities are of high interest for biodiversity research and conservation in Central Europe. However, historically, Central European beech forests were thought to harbor only relatively few species. Here, faunistic data of five beech forest reserves, which were generated as part of the Hessian strict forest reserves program, are analyzed to investigate diversity patterns of Hessian beech forests of low mountain ranges. We focus on species-level data from six organism groups: Aculeata, Araneae, Coleoptera, Heteroptera, Lumbricidae, and Macrolepidoptera. We show that with 2552 forest-dwelling species from these organism groups an unexpectedly high number of species was found in Hessian beech forests, and that a higher species richness can be expected in these groups. Observed species diversity ranges from 1245 to 1556 forest dwelling species in the five individual forest reserves. Overall, 36 % of the forest dwelling species of the considered species groups known from Germany were found with all applied methods in the forest reserves. Different forest reserves share 40-50 % of the species, representing 50-70 % of the species of the individual reserves, indicating high levels of regional and habitat-structure based differentiation. Only 21 % of the species are found in all five reserves. The low percentage of species found in all five reserves is, in addition to differing local conditions, probably a result of the communities being composed of few highly abundant and many rare species, leading to a high percentage of species only found by chance in our surveys. We also observe differences in community heterogeneity among the five reserves. Patterns differ between organism groups, clearly indicating that a focus on single taxa or a single indicator group falls short of revealing meaningful patterns. In spider communities, beta diversity is linked to the spatial distance between traps. In other organism groups community heterogeneity within reserves rather depends on structural heterogeneity. Species richness was associated with percentage of reserve area not covered with the most dominant habitat type, the deadwood amount, and with survey year. Being the potential natural vegetation of Germany and considering the unexpectedly high diversity of their associated fauna, beech forests bear a great conservation value. However, their widespread occurrence and dominance is likely to push them out of focus of conservation efforts. Yet protecting diverse and richly structured beech forests can contribute greatly to preserving the native arthropod fauna and should play a central role in biodiversity conservation efforts in Central Europe.

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iNEXT (iNterpolation and EXTrapolation) Online is the R-based interactive online version of iNEXT available via the link https://chao.shinyapps.io/iNEXTOnline/ or http://chao.stat.nthu.edu.tw/wordpress/software_download/. Clicking these links, you will be directed to the online interface window. Users do not need to learn/understand R to run iNEXT Online. The interactive web application was built using the Shiny (a web application framework). iNEXT features two statistical analyses (non-asymptotic and asymptotic) for species diversity based on Hill numbers: (1) A non-asymptotic approach based on interpolation and extrapolation iNEXT computes the estimated diversities for standardized samples with a common sample size or sample completeness. This approach aims to compare diversity estimates for equally-large (with a common sample size) or equally-complete (with a common sample coverage) samples; it is based on the seamless rarefaction and extrapolation sampling curves of Hill numbers for q = 0, 1 and 2. See Colwell et al. (2012), Chao and Jost (2012) and Chao et al. (2014) for pertinent background and methods. (2) An asymptotic approach to infer asymptotic diversity iNEXT computes the estimated asymptotic diversity profiles. It is based on statistical estimation of the true Hill number of any order q ≥ 0; see Chao and Jost (2015) for the statistical estimation detail.
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Chapter
The way a tree dies has important effects on the species composition in decaying wood. It makes a great difference whether the tree dies suddenly, for instance because of a storm or a wildfire, or whether it dies gradually from competition, drought or old age. Different types of mortality produce dead trees with contrasting qualities, and therefore different species initiate the decomposition process. Later the decaying wood goes through major physical and chemical changes and the species composition changes completely several times until the wood is totally decomposed. The species themselves interact in many ways, and complete food webs build up and wane during the decomposition process. In combination, the different mortality factors and the decay succession have a great impact on the biodiversity in dead wood. In addition to physically and chemically transforming the wood, the activity of wood decomposers also creates particular microhabitats such as sap exudations, insect galleries, space under loose bark, fungal fruiting bodies, rot holes and trunk cavities. Such microhabitats are important for a large number of species, and we describe them in detail in Chapter 7.
Chapter
It is evident that planet Earth hosts several million species. The actual number of species is unknown but a much cited study has calculated a global figure of 12.5 million species (Hammond, 1992), while a recent detailed revision came close to 11 million species (Chapman, 2009). In addition to these calculations, there are also estimates that have arrived at global figures as high as 30–100 million species (Erwin, 1982). Nobody has tried to estimate the number of saproxylic species on a global scale. This is quite understandable, since many groups are poorly investigated and large areas are minimally explored for wood-inhabiting species. But there is one region where most saproxylic species are well documented – in the Nordic countries of Europe. We therefore highlight some of this knowledge and present an overview of the diversity in various groups. Despite major knowledge gaps on a global scale, we also make an attempt to calculate the relevant numbers indicating the global diversity of saproxylic species. Saproxylic diversity in northern Europe There is a long and strong tradition of documenting species diversity in the Nordic countries of Sweden, Finland, Denmark and Norway. This tradition is rooted in the work of Carl von Linné, who made Sweden the European centre for alpha-taxonomy (i.e. the description of new species) in the 1700s. The Linnean school also had a great local impact in Sweden and the neighbouring countries. During the 1700s and 1800s, the majority of terrestrial species in the Nordic region were described and identification keys were made for large groups of insects and fungi.
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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.
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Large areas of montane forests are commercially harvested, while some other parts remain unmanaged. These conditions provide an opportunity to study the response of bird communities to forest management. Here we focused on the effects of tree species composition and tree age on bird species richness. We counted birds in two types of montane forest (beech and mixed) replicated in three age classes (managed 55-65 years, managed 85-95 years, unmanaged over 200 years) in the Vtačnik Mountains, Slovakia. Number of bird species at individual study sites (local richness) was predicted solely by the tree age and not by the forest type. Specifically, the number of species was highest in the oldest stands, while the stands of 55-65 and 85-95 years did not differ from each other. By contrast, forest type seems important for total bird species richness (number of species recorded in all study sites of a given type) with more species recorded in mixed forests than in beech forests. The local richness seems thus limited by the amount resources available at a given site, which is highest in the oldest stands irrespective to forest type, probably due to largest amount of food, dead wood or tree cavities, being particularly suitable for habitat specialists. However, larger species pool in mixed forest, enriched by birds adapted to coniferous trees, increases the total number of species observed in this type. We thus recommend to shift the harvest to the highest possible age and to include some other tree species into parts of beech monocultures.
Article
The issue investigated was whether a distinction can be made between centipede communities from different development phases of an unevenly-aged beech forest stand. The influence of stand structure on centipede diversity, resulting from a particular forest management practice, was evaluated. Soil samples were taken three times during 2000 from a beech stand with patches of different development phases near Ljubljana in Slovenia. Using the quadrat counts method, soil samples were taken with a sampling corer from adjoining selected patches in understorey re-initiation (gap-patch), juvenile, pole and timber phases of a forest. The characteristics of centipede communities and the similarities between them were then estimated by use of statistical methods (Jackknife estimate of species richness, Shannon-Wiener diversity index, Pielou's index of evenness, index of dominance, Renkonen index). The collection comprised 2075 centipedes representing 36 species. In a single patch, 24–28 species were found. Average centipede density was between 109 and 892 individuals per square metre. None of the common species was found exclusively in one development phase. The responses to forest development phases differed among species. Some species were considerably more abundant in older forest development phases, but most species did not show preference for a certain development phase. Differences between patches lay mostly in the distribution and abundance of species. Some samples from different patches are more similar than seasonal samples taken from the same patch. It was discovered that the centipede community structure in patches of an unevenly-aged stand does not only depend on a forest development phase. The inference was made that centipedes migrate between patches with different environmental conditions. Such an unevenly-aged stand can offer favourable conditions for more centipede species, so it was predicted that both alpha diversity and density are higher than they would be in an evenly-aged stand in the same area. Since small-scale heterogeneity within a forest stand enhances local species richness and supports viable populations of specialised species, maintenance of this heterogeneity should be the key focus in management operations within a forest stand.
Article
* Saproxylic beetle diversity monitoring provides a tool for estimating the efficiency of forest conservation measures. Flight interception traps are commonly employed to monitor beetle assemblages, although little explicit knowledge of the efficiency of this trapping method is available. * The present study investigated how slight changes in sampling effort can influence species richness and species composition of assemblages in data sets from standard window-flight traps. * At both trap and plot levels, an additional year or an additional trap provided a 50% increase in the number of species detected (a 75% increase for rare species) and resulted in a different estimated composition of the assemblages. Adding 2 or 3 years of sampling gave twice as many species and resulted in assemblages that were 50% dissimilar. Increases in the detection of species and the dissimilarity of assemblages were similarly affected along a gradient of forest conditions, suggesting that changes in sampling effort were not affected by forest condition. * At the forest level, year or trap replication provided smaller increases in species richness (31% and 25%, respectively). Within sites, distance measures in species composition between traps did not differ significantly when based on 1 or 2 years of data. Using two traps per plot compared with one trap influenced comparisons between stand types, based on species richness, in 25% of the cases. * Species detection was similarly increased by either year replication or trap replication. The results of the present study highlight the significant role played by finescale patterns of habitat structure and inter-annual variation with respect to determining catch size and assemblages of saproxylic species.
Article
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.