Spatial structure
Dotaz
Zobrazit nápovědu
BACKGROUND: Severe canopy-removing disturbances are native to many temperate forests and radically alter stand structure, but biotic legacies (surviving elements or patterns) can lend continuity to ecosystem function after such events. Poorly understood is the degree to which the structural complexity of an old-growth forest carries over to the next stand. We asked how pre-disturbance spatial pattern acts as a legacy to influence post-disturbance stand structure, and how this legacy influences the structural diversity within the early-seral stand. METHODS: Two stem-mapped one-hectare forest plots in the Czech Republic experienced a severe bark beetle outbreak, thus providing before-and-after data on spatial patterns in live and dead trees, crown projections, down logs, and herb cover. RESULTS: Post-disturbance stands were dominated by an advanced regeneration layer present before the disturbance. Both major species, Norway spruce (Picea abies) and rowan (Sorbus aucuparia), were strongly self-aggregated and also clustered to former canopy trees, pre-disturbance snags, stumps and logs, suggesting positive overstory to understory neighbourhood effects. Thus, although the disturbance dramatically reduced the stand's height profile with ~100% mortality of the canopy layer, the spatial structure of post-disturbance stands still closely reflected the pre-disturbance structure. The former upper tree layer influenced advanced regeneration through microsite and light limitation. Under formerly dense canopies, regeneration density was high but relatively homogeneous in height; while in former small gaps with greater herb cover, regeneration density was lower but with greater heterogeneity in heights. CONCLUSION: These findings suggest that pre-disturbance spatial patterns of forests can persist through severe canopy-removing disturbance, and determine the spatial structure of the succeeding stand. Such patterns constitute a subtle but key legacy effect, promoting structural complexity in early-seral forests as well as variable successional pathways and rates. This influence suggests a continuity in spatial ecosystem structure that may well persist through multiple forest generations.
Během stárnutí a při vývoji Alzheimerovy choroby (AD) se objevují poruchy prostorově navigace pravděpodobně spojené se změnami ve funkci hipokampu, čelního laloku a dalších mozkových struktur. U člověka zahrnují změny schopností navigace v prostoru v důsledku stárnutí jak prostorové, tak neprostorové strategie. Tyto změny jsou vysvětlovány omezením kognitivní kapacity, horší výkonností pracovní paměti, neefektivními prostorovými strategiemi nebo deficitem v použití alocentrické kognitivní mapy. U starších lidí byly popsány subjektivní potíže s navigací a vyhýbání se neznámým místům a cestám. Vážné poruchy prostorové orientace neslučující se samostatným životem jsou často popisovány u pacientů s AD a problémy s navigací v prostoru byly popsány i u pacientů s mírnou kognitivní poruchou. Desorientace u pacientů a AD může být vysvětlena pomocí deficitu ve složitějším vnímání, jako je vnímání optického toku, pomocí deficitu v prostorové paměti nebo pomocí obou. Tento přehled shrnuje nejdůležitější poznatky z literatury se zaměřením na neurální základy kognitivních změn a na možnosti časné detekce a vývoje AD pomocí vyšetření schopností navigace v prostoru.
Age dependent and Alzheimer's disease (AD) related deficits in spatial learning and memory are thought to be based on alterations in the hippocampus, frontal cortex and other brain structures which develop during aging and progression of AD. In human, the age related changes in spatial navigation comprise deficits in both route and place learning. These deficits have been explained by limits in cognitive capacity, working memory deficit, inefficient search strategies or deficits in allocentric cognitive mapping. Self -perceived deficits in navigation and behavioral patterns to avoid unfamiliar routes and places were described in elderly individuals. Dis abling topographic disorientation that interferes with independent living can be observed in many AD patients and difficulties with sp atial navigation were found even in patients with mild cognitive impairment. The disorientation in AD can be explained by higher orde r perceptual deficits including impaired visual motion processing and/or spatial memory deficits. The review will cover the current literature while focusing on the neural basis of the cognitive changes and the possibility of early detection and prediction of AD progres sion by spatial navigation abilities assessment.
- MeSH
- Alzheimerova nemoc etiologie patofyziologie MeSH
- financování organizované MeSH
- hipokampus fyziologie MeSH
- lidé MeSH
- neurokognitivní poruchy etiologie patofyziologie MeSH
- orientace MeSH
- poruchy paměti etiologie patofyziologie MeSH
- stárnutí fyziologie patologie MeSH
- vnímání prostoru fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- přehledy MeSH
... and the Compartmentalization of Cytoplasm -- Memory and Membranes: The Expression of Genetic and Spatial ... ... Poyton 15 -- Control and Regulation of the Spatial Organization of Membrane Components by Membrane-Membrane ... ... Granger 143 -- Interactions Between Actin Filaments and Membranes Give Spatial Organization to Cells ... ... McNiven 259 -- Organization of Nuclear Structure and the Control of Gene Action -- Strategies for Gene ... ... -- Harold Weintraub and Mark Grondine 353 -- The Three Dimensional Structural Networks of Cytoplasm ...
582 s. : il.
BACKGROUND: Subjective cognitive decline (SCD) may serve as a symptomatic indicator for preclinical Alzheimer's disease; however, SCD is a heterogeneous entity regarding clinical progression. We aimed to investigate whether spatial navigation could reveal subcortical structural alterations and the risk of progression to objective cognitive impairment in SCD individuals. METHODS: One hundred and eighty participants were enrolled: those with SCD (n = 80), normal controls (NCs, n = 77), and mild cognitive impairment (MCI, n = 23). SCD participants were further divided into the SCD-good (G-SCD, n = 40) group and the SCD-bad (B-SCD, n = 40) group according to their spatial navigation performance. Volumes of subcortical structures were calculated and compared among the four groups, including basal forebrain, thalamus, caudate, putamen, pallidum, hippocampus, amygdala, and accumbens. Topological properties of the subcortical structural covariance network were also calculated. With an interval of 1.5 years ± 12 months of follow-up, the progression rate to MCI was compared between the G-SCD and B-SCD groups. RESULTS: Volumes of the basal forebrain, the right hippocampus, and their respective subfields differed significantly among the four groups (p < 0.05, false discovery rate corrected). The B-SCD group showed lower volumes in the basal forebrain than the G-SCD group, especially in the Ch4p and Ch4a-i subfields. Furthermore, the structural covariance network of the basal forebrain and right hippocampal subfields showed that the B-SCD group had a larger Lambda than the G-SCD group, which suggested weakened network integration in the B-SCD group. At follow-up, the B-SCD group had a significantly higher conversion rate to MCI than the G-SCD group. CONCLUSION: Compared to SCD participants with good spatial navigation performance, SCD participants with bad performance showed lower volumes in the basal forebrain, a reorganized structural covariance network of subcortical nuclei, and an increased risk of progression to MCI. Our findings indicated that spatial navigation may have great potential to identify SCD subjects at higher risk of clinical progression, which may contribute to making more precise clinical decisions for SCD individuals who seek medical help.
Orchid mycorrhizal (OrM) fungi play a crucial role in the ontogeny of orchids, yet little is known about how the structure of OrM fungal communities varies with space and environmental factors. Previous studies suggest that within orchid patches, the distance to adult orchids may affect the abundance of OrM fungi. Many orchid species grow in species-rich temperate semi-natural grasslands, the persistence of which depends on moderate physical disturbances, such as grazing and mowing. The aim of this study was to test whether the diversity, structure and composition of OrM fungal community are influenced by the orchid patches and management intensity in semi-natural grasslands. We detected putative OrM fungi from 0 to 32 m away from the patches of host orchid species (Orchis militaris and Platanthera chlorantha) in 21 semi-natural calcareous grasslands using pyrosequencing. In addition, we assessed different ecological conditions in semi-natural grasslands but primarily focused on the effect of grazing intensity on OrM fungal communities in soil. We found that investigated orchid species were mostly associated with Ceratobasidiaceae and Tulasnellaceae and, to a lesser extent, with Sebacinales. Of all the examined factors, the intensity of grazing explained the largest proportion of variation in OrM fungal as well as total fungal community composition in soil. Spatial analyses showed limited evidence for spatial clustering of OrM fungi and their dependence on host orchids. Our results indicate that habitat management can shape OrM fungal communities, and the spatial distribution of these fungi appears to be weakly structured outside the orchid patches.
- MeSH
- Basidiomycota MeSH
- fylogeneze MeSH
- mykorhiza klasifikace MeSH
- Orchidaceae mikrobiologie MeSH
- pastviny * MeSH
- půdní mikrobiologie * MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Estonsko MeSH
The spatial spread of infectious disease is determined by spatial and social processes such as animal space use and family group structure. Yet, the impacts of social processes on spatial spread remain poorly understood and estimates of spatial transmission kernels (STKs) often exclude social structure. Understanding the impacts of social structure on STKs is important for obtaining robust inferences for policy decisions and optimizing response plans. We fit spatially explicit transmission models with different assumptions about contact structure to African swine fever virus surveillance data from eastern Poland from 2014 to 2015 and evaluated how social structure affected inference of STKs and spatial spread. The model with social structure provided better inference of spatial spread, predicted that approximately 80% of transmission events occurred within family groups, and that transmission was weakly female-biased (other models predicted weakly male-biased transmission). In all models, most transmission events were within 1.5 km, with some rare events at longer distances. Effective reproductive numbers were between 1.1 and 2.5 (maximum values between 4 and 8). Social structure can modify spatial transmission dynamics. Accounting for this additional contact heterogeneity in spatial transmission models could provide more robust inferences of STKs for policy decisions, identify best control targets and improve transparency in model uncertainty.
- MeSH
- africký mor prasat * epidemiologie MeSH
- nejistota MeSH
- prasata MeSH
- Sus scrofa MeSH
- virus afrického moru prasat * MeSH
- základní reprodukční číslo MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Host abundance and landscape structure often interact to shape spatial patterns of many wildlife diseases. Emergence, spread, and persistence of African swine fever (ASF) among wild boar in eastern Europe has raised questions on the factors underlying ASF dynamics in this novel host-pathogen system. This work identifies drivers of ASF occurrence in natural wild boar population. We evaluated factors shaping the probability of ASF-postitive wild boar during the first three years (2014-2016) of the ASF epidemic in Poland. We expected to observe positive effects of wild boar density, proportion of forested area, human activity, and proximity to previous infections on ASF case probability. We tested these predictions using the infection status of 830 wild boar samples and generalized mixed-effects models. The probability of ASF case increased from 3 to 20% as population density rose from 0.4 to 2 ind./km2. The positive effect of population density on ASF case probability was stronger at locations near previous ASF incidents. ASF was more likely to occur in forested areas, with the probability of detecting an ASF positive sample rising from 2 to 11% as forest cover around the sample increased from 0.5 to 100%. This pattern was consistent at both low and high wild boar densities. Indicators of human activity were poor predictors of ASF occurrence. Disease control efforts, such as culling and carcass search, should be focused on high-density populations where chances of detecting and eliminating ASF-positive wild boar are higher. The intensity of control measures should decrease with distance from the infected area to match the observed spatial pattern of ASF case probability. Woodlands represent areas of the highest risk of ASF case occurrence. Distribution and connectivity of suitable habitats over the landscape can be used to prioritize disease-management actions.
- MeSH
- africký mor prasat epidemiologie MeSH
- biologické modely MeSH
- divoká zvířata MeSH
- epidemie veterinární MeSH
- interakce hostitele a patogenu * MeSH
- prasata MeSH
- pravděpodobnost MeSH
- prostorová analýza MeSH
- Sus scrofa MeSH
- virus afrického moru prasat fyziologie MeSH
- životní prostředí MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Polsko MeSH
