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Although temporal heterogeneity is a well-accepted driver of biodiversity, effects of interannual variation in land-use intensity (LUI) have not been addressed yet. Additionally, responses to land use can differ greatly among different organisms; therefore, overall effects of land-use on total local biodiversity are hardly known. To test for effects of LUI (quantified as the combined intensity of fertilization, grazing, and mowing) and interannual variation in LUI (SD in LUI across time), we introduce a unique measure of whole-ecosystem biodiversity, multidiversity. This synthesizes individual diversity measures across up to 49 taxonomic groups of plants, animals, fungi, and bacteria from 150 grasslands. Multidiversity declined with increasing LUI among grasslands, particularly for rarer species and aboveground organisms, whereas common species and belowground groups were less sensitive. However, a high level of interannual variation in LUI increased overall multidiversity at low LUI and was even more beneficial for rarer species because it slowed the rate at which the multidiversity of rare species declined with increasing LUI. In more intensively managed grasslands, the diversity of rarer species was, on average, 18% of the maximum diversity across all grasslands when LUI was static over time but increased to 31% of the maximum when LUI changed maximally over time. In addition to decreasing overall LUI, we suggest varying LUI across years as a complementary strategy to promote biodiversity conservation.
Moving in the Anthropocene
(2018)
Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.
Home range estimation is routine practice in ecological research. While advances in animal tracking technology have increased our capacity to collect data to support home range analysis, these same advances have also resulted in increasingly autocorrelated data. Consequently, the question of which home range estimator to use on modern, highly autocorrelated tracking data remains open. This question is particularly relevant given that most estimators assume independently sampled data. Here, we provide a comprehensive evaluation of the effects of autocorrelation on home range estimation. We base our study on an extensive data set of GPS locations from 369 individuals representing 27 species distributed across five continents. We first assemble a broad array of home range estimators, including Kernel Density Estimation (KDE) with four bandwidth optimizers (Gaussian reference function, autocorrelated‐Gaussian reference function [AKDE], Silverman's rule of thumb, and least squares cross‐validation), Minimum Convex Polygon, and Local Convex Hull methods. Notably, all of these estimators except AKDE assume independent and identically distributed (IID) data. We then employ half‐sample cross‐validation to objectively quantify estimator performance, and the recently introduced effective sample size for home range area estimation ( N̂ area
) to quantify the information content of each data set. We found that AKDE 95% area estimates were larger than conventional IID‐based estimates by a mean factor of 2. The median number of cross‐validated locations included in the hold‐out sets by AKDE 95% (or 50%) estimates was 95.3% (or 50.1%), confirming the larger AKDE ranges were appropriately selective at the specified quantile. Conversely, conventional estimates exhibited negative bias that increased with decreasing N̂ area. To contextualize our empirical results, we performed a detailed simulation study to tease apart how sampling frequency, sampling duration, and the focal animal's movement conspire to affect range estimates. Paralleling our empirical results, the simulation study demonstrated that AKDE was generally more accurate than conventional methods, particularly for small N̂ area. While 72% of the 369 empirical data sets had >1,000 total observations, only 4% had an N̂ area >1,000, where 30% had an N̂ area <30. In this frequently encountered scenario of small N̂ area, AKDE was the only estimator capable of producing an accurate home range estimate on autocorrelated data.
Specialisation and diversity of multiple trophic groups are promoted by different forest features
(2019)
While forest management strongly influences biodiversity, it remains unclear how the structural and compositional changes caused by management affect different community dimensions (e.g. richness, specialisation, abundance or completeness) and how this differs between taxa. We assessed the effects of nine forest features (representing stand structure, heterogeneity and tree composition) on thirteen above- and belowground trophic groups of plants, animals, fungi and bacteria in 150 temperate forest plots differing in their management type. Canopy cover decreased light resources, which increased community specialisation but reduced overall diversity and abundance. Features increasing resource types and diversifying microhabitats (admixing of oaks and conifers) were important and mostly affected richness. Belowground groups responded differently to those aboveground and had weaker responses to most forest features. Our results show that we need to consider forest features rather than broad management types and highlight the importance of considering several groups and community dimensions to better inform conservation.
We studied the effect of three major forest management types (unmanaged beech, selection beech, and age class forests) and stand variables (SMId, soil pH, proportion of conifers, litter cover, deadwood cover, rock cover and cumulative cover of woody trees and shrubs) on bryophyte species richness in 1050 forest plots in three regions in Germany. In addition, we analysed the species richness of four ecological guilds of bryophytes according to their colonized substrates (deadwood, rock, soil, bark) and the number of woodland indicator bryophyte species. Beech selection forests turned out to be the most species rich management type, whereas unmanaged beech forests revealed even lower species numbers than age-class forests. Increasing conifer proportion increased bryophyte species richness but not the number of woodland indicator bryophyte species. The richness of the four ecological guilds mainly responded to the abundance of their respective substrate. We conclude that the permanent availability of suitable substrates is most important for bryophyte species richness in forests, which is not stringently linked to management type. Therefore, managed age-class forests and selection forests may even exceed unmanaged forests in bryophyte species richness due to higher substrate supply and therefore represent important habitats for bryophytes. Typical woodland indicator bryophytes and their species richness were negatively affected by SMId (management intensity) and therefore better indicate forest integrity than the species richness of all bryophytes. Nature conservation efforts should focus on the reduction of management intensity. Moreover, maintaining and increasing a variability of substrates and habitats, such as coarse woody debris, increasing structural heterogeneity by retaining patches with groups of old, mature to over-mature trees in managed forests, maintaining forest climate conditions by silvicultural methods that assure stand continuity, e.g. by selection cutting rather than clear cutting and shelterwood logging might promote bryophyte diversity and in particular the one of woodland indicator bryophytes.
The functionalization of polyelectrolyte multilayers often implies the use of bulky functional fragments, attached to a standard polyelectrolyte matrix. Despite of the high density of non-charged, often hydrophobic substituents, regular film growth by sequential adsorption proceeds easily when an appropriate polyelectrolyte counter ion is chosen. However, the functional fragments may cluster or aggregate. This complication is particularly evident when using chromophores and fluorophores as bulky pendant groups. Attention has to be paid to this phenomenon for the design of functional polyelectrolyte films, as aggregation may modify crucially the properties. The use of charged spacer groups does not necessarily suppress the aggregation of functional side groups. Still, clustering and aggregation depend on the detailed system employed, and are not obligatory. In the case of cationic poly(acrylamide)s labeled with naphthalene and pyrene fluorophores, for instance, the polymers form intramolecular hydrophobic associates in solution, as indicated by strong excimer formation. But the polymers can undergo a conformational rearrangement upon adsorption so that they are decoiled in the adsorbed films. Analogous observations are made for polyanions bearing mesogenic biphenyls fragments. In contrast, polycations functionalized with the dye coumarin 343 show little aggregation in solution, but a marked aggregation in the ESA films
Zusammenfassung In der naturschutzrechtlichen Eingriffsregelung wird das Landschaftsbild gegenüber den Belangen des Naturhaushalts oft nachrangig behandelt, obwohl es von den Voraussetzungen des Bundesnaturschutzgesetzes her gleichermaßen in alle Schritte der Folgenbewältigung einzubeziehen ist. Für diese Schritte werden exemplarisch rechtliche Rahmenbedingungen und fachliche Anforderungen aufgezeigt. Ingesamt wird so eine strukturierte Herangehensweise deutlich, die über die einzelnen Arbeitsschritte der Erfassung des Ist-Zustandes, der Aufstellung eines Zielkonzeptes, der Ableitung von Vorkehrungen zur Vermeidung sowie der Begründung von Maßnahmen zur landschaftsgerechten Wiederherstellung und Neugestaltung des Landschaftsbildes hinweg durchgängig auf denselben Beschreibungsmerkmalen aufbaut und damit einen durchgängigen Ableitungszusammenhang von den ermittelten Beeinträchtigungen des Landschaftsbildes zu darauf Bezug nehmenden Maßnahmen begründet. Wesentlich ist, dass dabei die Charakteristik des jeweiligen Landschaftsraumes im Vordergrund steht und dass nicht nur einzelne Beeinträchtigungen betrachtet, sondern diese jeweils in ihrem Zusammenwirken auf den wahrgenommenen Raumeindruck beleuchtet werden. Ein wichtiger Aspekt ist zudem die Rechtssicherheit, weshalb sich der verwendete Rahmen eng an die Terminologie des Bundesnaturschutzgesetzes anlehnt Summary How to deal with Disturbance of the Visual Landscape by Traffic Projects? Legal framework conditions and special requirements The impact regulation of nature conservation only gives inferior treatment to the visual landscape compared to other natural resources although nature conservation legislation requires its equal integration into all steps of consequential dealing. For these steps the study shows exemplary legal framework conditions and specialist requirements. They should make clearer a structural approach including individual working steps, such as recording of present site conditions, establishment of a target concept, derivation of measures of avoidance and justification of measures for a sensitive regeneration and design of the visual landcape. The approach continuously bases on the same features of description, leading to a consistent connection between identified disturbances of the visual landscape and related measures. The focus of attemtion should be given to the characteristics of the respective landscape and the analysis should not only consider disturbances or compensation measures individually but also in combination with the general spatial perception. Another important aspect is the legal security; therefore the text closely follows the terminology of the Federal Nature Conservation Legislation.
Auch nach über 25 Jahren Anwendung der Eingriffsregelung nehmen landschaftsästhetische Aspekte häufig noch eine deutlich schwächere Stellung gegenüber den Belangen des Naturhaushalts ein. Als besonders schwierig erweist sich die Erfassung und Bewertung des Landschaftsbildes und - ausgehend von den konkreten Beeinträchtigungen, die vom Vorhaben ausgehen - die Ableitung wirkungsbezogener Kompensationsmaßnahmen. Mit der vorliegenden Veröffentlichung wird eine Handlungsanleitung zur Erfassung und Beschreibung des Landschaftsbildes vorgelegt, die insbesondere auf eine schlüssige Begründung und Herleitung von Vorkehrungen zur Vermeidung sowie von Ausgleichs- und Ersatzmaßnahmen zur landschaftsgerechten Wiederhertsellung und Neugestaltung des Landschaftsbildes abzielt. Wesentlich ist, dass dabei der notwendige Bezug auf die Charakteristik des jeweiligen Landschaftsraums im Vordergrund steht. Daneben werden die Einsetzbarkeit verschiedener Methoden der Landschaftsvisualisierung im Arbeitsablauf der Eingriffsregelung beleuchtet, Hinweise für entsprechende Standards begründet sowie Empfehlungen für Nachkontrollen von Kompensationsmaßnahmen begründet.
Femtosecond x-ray diffraction reveals a liquid-liquid phase transition in phase-change materials
(2019)
In phase-change memory devices, a material is cycled between glassy and crystalline states. The highly temperature-dependent kinetics of its crystallization process enables application in memory technology, but the transition has not been resolved on an atomic scale. Using femtosecond x-ray diffraction and ab initio computer simulations, we determined the time-dependent pair-correlation function of phase-change materials throughout the melt-quenching and crystallization process. We found a liquid-liquid phase transition in the phase-change materials Ag4In3Sb67Te26 and Ge15Sb85 at 660 and 610 kelvin, respectively. The transition is predominantly caused by the onset of Peierls distortions, the amplitude of which correlates with an increase of the apparent activation energy of diffusivity. This reveals a relationship between atomic structure and kinetics, enabling a systematic optimization of the memory-switching kinetics.