homogenization
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Environmental change has reshuffled communities often causing taxonomic homogenization rather than differentiation. Some studies suggest that this increasing similarity of species composition between communities is accompanied by an increase in similarity of trait composition-functional homogenization-although different methodologies have failed to come to any consistent conclusions. Functional homogenization could have a large effect on ecosystem functioning and stability. Here, we use the general definition of homogenization as "reduced spatial turnover over time" to compare changes in Simpson's beta diversity (taxonomic turnover) with changes in Rao's quadratic entropy beta diversity (functional turnover) in British breeding birds at three spatial scales. Using biotic and climatic variables, we identify which factors may predispose a site to homogenization. The change in turnover measures between two time periods, 20 years apart, was calculated. A null model approach was taken to identify occurrences of functional homogenization and differentiation independent of changes in taxonomic turnover. We used conditional autoregressive models fitted using integrated nested Laplace approximations to determine how environmental drivers and factors relating to species distributions affect changes in spatial turnover of species and functional diversity. The measurement of functional homogenization affects the chance of rejection of the null models, with many sites showing taxonomic homogenization unaccompanied by functional homogenization, although occurrence varies with spatial scale. At the smallest scale, while temperature-related variables drive changes in taxonomic turnover, changes in functional turnover are associated with variation in growing degree days; however, changes in functional turnover become more difficult to predict at larger spatial scales. Our results highlight the multifactorial processes underlying taxonomic and functional homogenization and that redundancy in species traits may allow ecosystem functioning to be maintained in some areas despite changes in species composition.
- Klíčová slova
- biotic homogenization, climate, ecological traits, functional diversity, local species distribution,
- Publikační typ
- časopisecké články MeSH
The degradation of natural habitats is causing ongoing homogenization of biological communities and declines in terrestrial insect biodiversity, particularly in agricultural landscapes. Orthoptera are focal species of nature conservation and experienced significant diversity losses over the past decades. However, the causes underlying these changes are not yet fully understood. We analysed changes in Orthoptera assemblages surveyed in 1988, 2004 and 2019 on 198 plots distributed across four major grassland types in Central Europe. We demonstrated compositional differences in Orthoptera assemblages found in wet, dry and mesic grasslands, as well as ruderal habitats decreased, indicating biotic homogenization. However, mean α-diversity of Orthoptera assemblages increased over the study period. We detected increasing numbers of species with preferences for higher temperatures in mesic and wet grasslands. By analysing the temperature, moisture and vegetation preferences of Orthoptera, we found that additive homogenization was driven by a loss of species adapted to extremely dry and nitrogen-poor habitats and a parallel spread of species preferring warmer macroclimates.
- Klíčová slova
- additive homogenization, insect decline, timeseries,
- MeSH
- biodiverzita MeSH
- ekosystém MeSH
- Orthoptera * MeSH
- pastviny * MeSH
- teplota MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Our planet is facing significant changes of biodiversity across spatial scales. Although the negative effects of local biodiversity (α diversity) loss on ecosystem stability are well documented, the consequences of biodiversity changes at larger spatial scales, in particular biotic homogenization, that is, reduced species turnover across space (β diversity), remain poorly known. Using data from 39 grassland biodiversity experiments, we examine the effects of β diversity on the stability of simulated landscapes while controlling for potentially confounding biotic and abiotic factors. Our results show that higher β diversity generates more asynchronous dynamics among local communities and thereby contributes to the stability of ecosystem productivity at larger spatial scales. We further quantify the relative contributions of α and β diversity to ecosystem stability and find a relatively stronger effect of α diversity, possibly due to the limited spatial scale of our experiments. The stabilizing effects of both α and β diversity lead to a positive diversity-stability relationship at the landscape scale. Our findings demonstrate the destabilizing effect of biotic homogenization and suggest that biodiversity should be conserved at multiple spatial scales to maintain the stability of ecosystem functions and services.
- Klíčová slova
- biotic homogenization, grassland experiment, landscape, scale, spatial asynchrony, β diversity, γ diversity, γ stability,
- MeSH
- biodiverzita * MeSH
- ekosystém * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
A combined experimental and numerical study on titanium porous microstructures intended to interface the bone tissue and the solid homogeneous part of a modern dental implant is presented. A specific class of trabecular geometries is compared to a gyroid structure. Limitations associated with the application of the adopted selective laser melting technology to small microstructures with a pore size of 500 μm are first examined experimentally. The measured effective elastic properties of trabecular structures made of Ti6Al4V material support the computational framework based on homogenization with the difference between the measured and predicted Young's moduli of the Dode Thick structure being less than 5%. In this regard, the extended finite element method is promoted, particularly in light of the complex sheet gyroid studied next. While for plastic material-based structures a close match between experiments and simulations was observed, an order of magnitude difference was encountered for titanium specimens. This calls for further study and we expect to reconcile this inconsistency with the help of computational microtomography.
- Klíčová slova
- FEM, X-FEM, dental implant, homogenization, mechanical properties, porous material, selective laser melting, titanium trabecular and gyroid structures,
- Publikační typ
- časopisecké články MeSH
This study was conducted to determine the effect of 1-stage homogenization (OSH) and 2-stage homogenization (TSH) and the addition of polysaccharides [κ-carrageenan (CR) or furcellaran (FR) at levels ranging from 0.000 to 1.000% (wt/wt)] on the physicochemical, viscoelastic, and mechanical vibration damping properties of processed cheese sauces (PCS) after 30 d of storage (6 ± 2°C). The basic chemical properties (pH, dry matter content) were similar for all tested samples. Viscoelastic measurements indicated that PCS rigidity was directly proportional to increasing CR or FR concentration and to the application of homogenization. The interactions between the application of homogenization and the concentration of polysaccharides used were also significant. Compared with OSH, TSH did not lead to any further increase in the rigidity. The preceding results were also supported by data obtained from a nondestructive method of mechanical vibration damping. No changes in water activity were observed in any PCS sample. Overall, the addition of FR or CR appeared to be highly suitable for increasing the emulsion stability of PCS. If PCS products with softer consistency are desired, then a concentration of CR/FR ≤0.250% (wt/wt) could be recommended together with OSH/TSH. For products for which a firmer PCS consistency is required, the addition of CR in concentrations of ≥0.500% (wt/wt) or FR in concentrations of ≥1.000% (wt/wt) together with OSH is recommended. Finally, as the concentration of polysaccharides increased, a darker PCS color was observed.
- Klíčová slova
- furcellaran, homogenization, processed cheese sauce, rheological properties, κ-carrageenan,
- MeSH
- karagenan MeSH
- manipulace s potravinami metody MeSH
- polysacharidy MeSH
- reologie MeSH
- sýr * analýza MeSH
- thyreotropin MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- karagenan MeSH
- polysacharidy MeSH
- thyreotropin MeSH
The causes of decreasing plant species richness include abandonment of traditional management and the spread of invasive species, even in alpine habitats. Studies on the restoration and management of alpine habitats are predominantly focused on vascular plants, although an important part of alpine vegetation and its diversity is formed by bryophytes. We used bryophytes to indicate changes that occur after the clearcutting of nonindigenous dwarf pine (Pinus mugo Turra) and attempted to reveal the community to which the development of bryophyte species structure was directed. We compared species richness and composition between surveys to test for changes in spatial heterogeneity bryophyte communities. We also tried to reveal the main ecological drivers of the restoration process. The study was performed in the (sub)alpine area of the Eastern High Sudetes Mts. (the Czech Republic). We estimated bryophyte species cover and compared the composition of the bryophyte community in autochthonous grassland areas, areas under the dwarf pine canopy, and clearcut areas to reveal the pattern of shifts 9 years after the treatment. We also measured soil characteristics to reveal the environmental habitat conditions. Evidence of taxonomic homogenization of habitat after dwarf pine removal was found. Light conditions and attributes of litter were the driving factors of successional changes in the bryophyte communities, which led to taxonomic homogenization. This finding explains the slow restoration process due to dwarf pine legacy on the clearcut area. The succession trends were also shaped by unobserved factors, such as climate change and environmental eutrophication. We highly recommended active management and long-term monitoring.
- Klíčová slova
- Clearcut, Dwarf pine, Environmental characteristics, Liverwort, Management, Successional trend,
- MeSH
- biodiverzita MeSH
- borovice MeSH
- Bryophyta * klasifikace MeSH
- klimatické změny MeSH
- pastviny * MeSH
- regenerace a remediace životního prostředí * MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Česká republika MeSH
The perfectly conducting stacked fishnet metamaterial is studied in this paper. The analysis is based on a combination of the mode matching method together with the generalized eigenvalue problem, and takes into account wave propagation along all three Cartesian axes. The analysis has been developed for a fishnet of square lateral periodicity and for two particular polarizations, namely TE and TM, corresponding to the two most common excitations. The 1D and 2D dispersion characteristics are calculated for both polarizations, showing that the TM waves undergo negative refraction in a narrow frequency band just below Wood's anomaly, whereas TE polarized waves exhibit ordinary positive refraction. Finally, possible homogenization of the fishnet metamaterial is considered, showing that only for small angles of incidence and in the immediate vicinity of Wood's anomaly can the fishnet be seen as homogenizable uniaxial medium.
- MeSH
- design vybavení MeSH
- krystalizace přístrojové vybavení metody MeSH
- optika a fotonika přístrojové vybavení metody MeSH
- radiační rozptyl MeSH
- refraktometrie přístrojové vybavení metody MeSH
- teoretické modely MeSH
- vyrobené materiály * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Dissociative neurological symptom disorder, also called functional neurological symptom disorder or conversion disorder, presents characteristics that are incongruent with medical or neurological conditions. This study investigates whether sensory exposure to red light and white noise can trigger dissociative and conversion symptoms. Consequently, the reported somatosensory alterations significantly challenge current diagnostic protocols. In this study, we record inceptive evidence of conversion symptoms from a sample of 61 healthy university students who reported dissociative states after the Ganzfeld audio-visual homogenization condition. In the Ganzfeld condition, individuals experienced increased conversion and decreased depersonalization when red light and white noise were used as stimuli. Our findings correlate with those of previous studies that highlighted red light's ability to significantly trigger negative effects. Simultaneously, we found that the multimodal Ganzfeld condition may decrease identity confusion. Additionally, dissociative states among these participants were consistent with trauma symptoms, emphasizing the predispositions that may impact executive functioning. We further highlight that the somatosensory alterations may be a result of endogenous and exogenous attentional orientation. This investigation elucidated potential triggers and effects of conversion symptoms that could be important for understanding dissociative psychopathology.
- Klíčová slova
- conversion, dissociation, investigation, multimodal Ganzfeld, predispositions,
- MeSH
- depersonalizace patofyziologie MeSH
- disociační poruchy * patofyziologie psychologie MeSH
- dospělí MeSH
- konverzní poruchy * patofyziologie psychologie MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- sluchová percepce * fyziologie MeSH
- zraková percepce * fyziologie MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- mladiství MeSH
- mladý dospělý MeSH
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
Biotic homogenization appears to be a global consequence of anthropogenic change. However, the underlying environmental factors contributing to homogenization are difficult to identify because their effects usually interact and confound each other. This can be the reason why there is very little evidence on the role of climate warming in homogenization. By analysing macroinvertebrate assemblages in 65 streams that were as close to natural conditions as possible, we avoided the confounding effects of common anthropogenic stressors. This approach resulted in revealing a significant effect of increased temperature (both summer and winter) on changes in macroinvertebrate compositional over the past two decades. However, homogenization was significant only at opposite ends of the river continuum (submontane brooks, low-altitude rivers). Surprisingly, species of native origin predominated overall, increasing in frequency and abundance ("winners"), while only a minority of species declined or disappeared ("losers"). We hypothesise that undisturbed conditions mitigate species declines and thus homogenization, and that the temperature increase has so far been beneficial to most native species. Although we may have only captured a transitional state due to extinction debt, this underscores the importance of maintaining ecological conditions in stream to prevent species loss due to climate change.
- MeSH
- bezobratlí * MeSH
- ekosystém * MeSH
- klimatické změny MeSH
- monitorování životního prostředí metody MeSH
- řeky MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Despite its negative impacts on the environment and biodiversity, tree plantations can contribute to biodiversity conservation in fragmented landscapes, as they harbor many native species. In this study, we investigated the impact of Eucalyptus plantations on the taxonomic and functional diversity of ant communities, comparing ant communities sampled in managed and unmanaged (abandoned for 28 years) Eucalyptus plantations, and native Atlantic rain forests. Eucalyptus plantations, both managed and unmanaged, reduced the functional diversity and increased the similarity between ant communities leading to functional homogenization. While communities in managed plantations had the lowest values of both taxonomic and functional ant diversities, ant communities from unmanaged plantations had similar values of species richness, functional redundancy and Rao's Q compared to ant communities from forest patches (although functional richness was lower). In addition, communities in unmanaged Eucalyptus plantations were taxonomically and functionally more similar to communities located in managed plantations, indicating that Eucalyptus plantations have a severe long-term impact on ant communities. These results indicate that natural regeneration may mitigate the impact of Eucalyptus management, particularly regarding the functional structure of the community (α diversity), although it does not attenuate the effects of long term homogenization in community composition (β diversity).
