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Spatiotemporal Dynamics (spatiotemporal + dynamics)
Selected AbstractsSpatiotemporal dynamics of evapotranspiration at the Glacial Ridge prairie restoration in northwestern MinnesotaHYDROLOGICAL PROCESSES, Issue 7 2006Assefa M. Melesse Abstract Among the various indicators of success in wetland restoration, hydrology is the most important and relatively easy to monitor. Evapotranspiration (ET) was used to assess the ecohydrologic changes at the Glacial Ridge prairie restoration site in northwestern Minnesota. Twelve Landsat images from 2000,03 for the months of June, July and August were used to study the spatial ET changes. Spatial monthly and seasonal ET were estimated using a surface energy budget technique from Landsat images. Five sub-basins within the study area were delineated to represent the different conditions of the wetlands. Their spatial and temporal ET responses to the restoration activities (native species planting, burning and ditch closures) were studied. Spatial statistics showing mean and standard deviation of monthly ET were computed. Comparisons were made between these watersheds and the preserved sub-watershed of the study area. The average annual ET increases for the five sub-basins were in the range of 9% (2002,03) to 25% (2001,02). Over the study period, ET increased by nearly 50%. After considering the effect of variations in precipitation, wind speed and solar radiation on the resulting ET, the results show that ET increased in recent years as result of the restoration activities. Copyright © 2005 John Wiley & Sons, Ltd. [source] Spatiotemporal dynamics of lipid signaling: Protein kinase C as a paradigmIUBMB LIFE, Issue 12 2008Lisa L. Gallegos Abstract The lipid second messenger diacylglycerol (DAG) controls the rate, amplitude, duration, and location of protein kinase C (PKC) activity in the cell. There are three classes of PKC isozymes and, of these, the conventional and novel isozymes are acutely controlled by DAG. The kinetics of DAG production at various intracellular membranes, the intrinsic affinity of specific isoforms for DAG-containing membranes, the coordinated use of additional membrane-binding modules, the intramolecular regulation of DAG sensitivity, and the competition from other DAG-responsive proteins together result in a unique, context-dependent activation signature for each isoform. This review focuses on the spatiotemporal dynamics of PKC activation and how it is controlled by lipid second messengers. © 2008 IUBMB IUBMB Life, 60(12): 782,789, 2008 [source] The spatiotemporal dynamics of a primary successionJOURNAL OF ECOLOGY, Issue 2 2008N. A. Cutler Summary 1Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template. 2These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850-year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean-variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations. 3The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches (,Pioneer colonization stage', < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet (,Pioneer expansion stage', 20,100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix (,Higher plant colonization stage', 100,600 years). Over time, heterogeneity re-emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate (,Differentiation stage', > 600 years). 4Synthesis. The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro-scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso-scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment. [source] Infants' Evolving Representations of Object Motion During Occlusion: A Longitudinal Study of 6- to 12-Month-Old InfantsINFANCY, Issue 2 2004Gustaf Gredebäck Infants' ability to track temporarily occluded objects that moved on circular trajectories was investigated in 20 infants using a longitudinal design. They were first seen at 6 months and then every 2nd month until the end of their 1st year. Infants were presented with occlusion events covering 20% of the target's trajectory (effective occlusion interval ranged from 500,4,000 msec). Gaze was measured using an ASL 504 infrared eye-tracking system. Results effectively demonstrate that infants from 6 months of age can represent the spatiotemporal dynamics of occluded objects. Infants at all ages tested were able to predict, under certain conditions, when and where the object would reappear after occlusion. They moved gaze accurately to the position where the object was going to reappear and scaled their timing to the current occlusion duration. The average rate of predictive gaze crossings increased with occlusion duration. These results are discussed as a 2-factor process. Successful predictions are dependent on strong representations, themselves dependent on the richness of information available during encoding and graded representations. [source] Spatiotemporal dynamics of lipid signaling: Protein kinase C as a paradigmIUBMB LIFE, Issue 12 2008Lisa L. Gallegos Abstract The lipid second messenger diacylglycerol (DAG) controls the rate, amplitude, duration, and location of protein kinase C (PKC) activity in the cell. There are three classes of PKC isozymes and, of these, the conventional and novel isozymes are acutely controlled by DAG. The kinetics of DAG production at various intracellular membranes, the intrinsic affinity of specific isoforms for DAG-containing membranes, the coordinated use of additional membrane-binding modules, the intramolecular regulation of DAG sensitivity, and the competition from other DAG-responsive proteins together result in a unique, context-dependent activation signature for each isoform. This review focuses on the spatiotemporal dynamics of PKC activation and how it is controlled by lipid second messengers. © 2008 IUBMB IUBMB Life, 60(12): 782,789, 2008 [source] Breeding birds on small islands: island biogeography or optimal foraging?JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006GARETH J. RUSSELL Summary 1We test MacArthur and Wilson's theory about the biogeography of communities on isolated habitat patches using bird breeding records from 16 small islands off the coasts of Britain and Ireland. 2A traditional examination of patterns of species richness on these islands suggests that area and habitat diversity are important predictors, but that isolation and latitude have a negligible impact in this system. 3Unlike traditional studies, we directly examine the fundamental processes of colonization and local extinction (cessation of breeding), rather than higher-order phenomena such as species richness. 4We find that many of MacArthur and Wilson's predictions hold: colonization probability is lower on more isolated islands, and extinction probability is lower on larger islands and those with a greater diversity of habitats. 5We also find an unexpected pattern: extinction probability is much lower on more isolated islands. This is the strongest relationship in these data, and isolation is the best single predictor of colonization and extinction. 6Our results show that examination of species richness alone is misleading. Isolation has a strong effect on both of the dynamic processes that underlie richness, and in this system, the reductions in both colonization and extinction probability seen on more distant islands have opposing influences on species richness, and largely cancel each other out. 7We suggest that an appropriate model for this system might be optimal foraging theory, which predicts that organisms will stay longer in a resource patch if the distance to a neighbouring patch is large. If nest sites and food are the resources in this system, then optimal foraging theory predicts the pattern we observe. 8We advance the hypothesis that there is a class of spatial systems, defined by their scale and by the taxon under consideration, at which decision-making processes are a key driver of the spatiotemporal dynamics. The appropriate theory for such systems will be a hybrid of concepts from biogeography/metapopulation theory and behavioural ecology. [source] The spatiotemporal dynamics of a primary successionJOURNAL OF ECOLOGY, Issue 2 2008N. A. Cutler Summary 1Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template. 2These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850-year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean-variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations. 3The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches (,Pioneer colonization stage', < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet (,Pioneer expansion stage', 20,100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix (,Higher plant colonization stage', 100,600 years). Over time, heterogeneity re-emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate (,Differentiation stage', > 600 years). 4Synthesis. The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro-scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso-scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment. [source] 84 Linking environmental forcing, kelp forest habitat dynamics, and community structure in the northeast pacificJOURNAL OF PHYCOLOGY, Issue 2003B.P. Kinlan Habitat-forming species of large brown macroalgae (e.g., kelps) often differ from associated benthic species in resource requirements, sources of disturbance, and dispersal ability. Differences in environmental drivers and demographic processes may cause these habitats to fluctuate at spatial and temporal scales that differ from the "optimal" scale that would promote maximum abundance of any particular associate species. As a result, the spatiotemporal dynamics of habitat may exert important effects on benthic community structure and composition. To quantify the spatial and temporal dynamics of giant kelp (Macrocystis pyrifera), a key habitat-former in the NE Pacific, I analyzed a 34-year monthly time series of estimated canopy biomass spanning ,1500 km of coastline (7° of latitude) and digital maps of annual maximum canopy cover. Canopy biomass varied interannually at dominant periods of 4,5 y, 11,13 y and ,20 y, and spatial scales ranging from local (,30 km) to mesoscale (,100,150 km) and regional (,330 km). Temporal dynamics were strongly related to basin-scale climate fluctuations (El Niño-Southern Oscillation, Pacific Decadal Oscillation) and spatial patterns were correlated with coastline geomorphology. Digital canopy maps reveal that changes in biomass are associated with shifts in the spatial structure of the kelp habitat. Long-term subtidal community monitoring data from areas with markedly different spatial and temporal scales of kelp forest habitat structure reveal a complex but important influence of habitat dynamics on the distribution of life histories within kelp-associated communities. Future changes in the dynamics of Pacific climate fluctuations may have important implications for kelp forest community structure. [source] Exploring spatiotemporal patterns in early stages of primary succession on former lignite mining sitesJOURNAL OF VEGETATION SCIENCE, Issue 2 2008Birgit Felinks Abstract Questions: 1. Does random colonization predominate in early stages of primary succession? 2. Do pioneer species facilitate the establishment of later arriving species? 3. Does an initially random distribution change to an aggregated pattern with ongoing succession? Location: Lignite mining region of Lower Lusatia, eastern Germany. Methods: Individual plants were mapped along a 2 m × 28 m transect during three successive years and classified into two groups (1) the pioneer Corynephorus canescens and (2),all other species'. Using the pair-correlation function, univariate point pattern analysis was carried out by applying a heterogeneous Poisson process as null model. Bivariate analysis and a toroidal shift null model were applied to test for independence between the spatial patterns of the two groups separately for each year, as well by exploring spatiotemporal patterns from different years. Results: In the first year Corynephorus and ,all other species' showed an aggregated pattern on a spatial scale > 40 cm and in the second and third years a significant attraction for distances between 4 and 12 cm, with an increasing radius in the third year. The analyses of interspecific spatiotemporal dynamics revealed a change from independence to attraction between distances of 4 cm and 16 cm when using Corynephorus as focal species. However, applying ,all other species' as focal points results in a significant attraction at distances up to 60 cm in the first year and a diminishing attraction in the second and third years with distances , 6 cm. Conclusions: Facilitative species-species interactions are present in early stages of primary succession, resulting mainly from pioneer species acting as physical barriers and their ability to capture diaspores being drifted by secondary dispersal along the substrate surface. However, due to gradual establishment of perennial species and their ability of lateral extension by vegetative dispersal, facilitation may influence spatial pattern formation predominantly on short temporal and fine spatial scales. [source] 454 Pyrosequencing analyses of forest soils reveal an unexpectedly high fungal diversityNEW PHYTOLOGIST, Issue 2 2009M. Buée Summary ,,Soil fungi play a major role in ecological and biogeochemical processes in forests. Little is known, however, about the structure and richness of different fungal communities and the distribution of functional ecological groups (pathogens, saprobes and symbionts). ,,Here, we assessed the fungal diversity in six different forest soils using tag-encoded 454 pyrosequencing of the nuclear ribosomal internal transcribed spacer-1 (ITS-1). No less than 166 350 ITS reads were obtained from all samples. In each forest soil sample (4 g), approximately 30 000 reads were recovered, corresponding to around 1000 molecular operational taxonomic units. ,,Most operational taxonomic units (81%) belonged to the Dikarya subkingdom (Ascomycota and Basidiomycota). Richness, abundance and taxonomic analyses identified the Agaricomycetes as the dominant fungal class. The ITS-1 sequences (73%) analysed corresponded to only 26 taxa. The most abundant operational taxonomic units showed the highest sequence similarity to Ceratobasidium sp., Cryptococcus podzolicus, Lactarius sp. and Scleroderma sp. ,,This study validates the effectiveness of high-throughput 454 sequencing technology for the survey of soil fungal diversity. The large proportion of unidentified sequences, however, calls for curated sequence databases. The use of pyrosequencing on soil samples will accelerate the study of the spatiotemporal dynamics of fungal communities in forest ecosystems. [source] Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forestNEW PHYTOLOGIST, Issue 3 2007Björn D. Lindahl Summary ,,Our understanding of how saprotrophic and mycorrhizal fungi interact to re-circulate carbon and nutrients from plant litter and soil organic matter is limited by poor understanding of their spatiotemporal dynamics. ,,In order to investigate how different functional groups of fungi contribute to carbon and nitrogen cycling at different stages of decomposition, we studied changes in fungal community composition along vertical profiles through a Pinus sylvestris forest soil. We combined molecular identification methods with 14C dating of the organic matter, analyses of carbon:nitrogen (C:N) ratios and 15N natural abundance measurements. ,,Saprotrophic fungi were primarily confined to relatively recently (< 4 yr) shed litter components on the surface of the forest floor, where organic carbon was mineralized while nitrogen was retained. Mycorrhizal fungi dominated in the underlying, more decomposed litter and humus, where they apparently mobilized N and made it available to their host plants. ,,Our observations show that the degrading and nutrient-mobilizing components of the fungal community are spatially separated. This has important implications for biogeochemical studies of boreal forest ecosystems. [source] Mathematical modeling of reactive transport of anti-tumor drugs through electro-active membranesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009Parag Saurabh Abstract We present a mathematical modeling and design of an implantable polymer membrane-based drug-release device that uses alternate voltage scans across the electro-active membrane for delivery and reactive uptake of anionic anti-tumor drugs. Our mathematical model comprises Poisson,Boltzmann, Nernst,Planck and Diffusion,Reaction equations written for three compartments, namely, the drug reservoir, the polymer membrane and the diseased tissue, with the governing equations for the compartments being linked to each other through the boundary conditions. An analytical solution for the three-compartment model has been obtained using Laplace transforms and residue integration. We use this solution to quantify the various parameters controlling the spatiotemporal dynamics of drug delivery and analyze the efficacy of the reactive transport process for an anionic chemotherapeutic drug, Irinotecan-HCl, commercially also known as CPT-11. We show that a ,smart pill' with optimal drug efficacy may be designed by altering the thickness and the diffusivity of the electro-active membrane, and by tuning the applied voltage and the duration of the positive and the negative voltage scans such that the drug concentration in the tumor tissue is maintained within its therapeutic range. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Regulatory mechanisms and functions of intermediate filaments: A study using site- and phosphorylation state-specific antibodiesCANCER SCIENCE, Issue 3 2006Ichiro Izawa Intermediate filaments (IF) form the structural framework of the cytoskeleton. Although histopathological detection of IF proteins is utilized for examining cancer specimens as reliable markers, the molecular mechanisms by which IF are involved in the biology of cancer cells are still unclear. We found that site-specific phosphorylation of IF proteins induces the disassembly of filament structures. To further dissect the in vivo spatiotemporal dynamics of IF phosphorylation, we developed site- and phosphorylation state-specific antibodies. Using these antibodies, we detected kinase activities that specifically phosphorylate type III IF, including vimentin, glial fibrillary acidic protein and desmin, during mitosis. Cdk1 phosphorylates vimentin-Ser55 from prometaphase to metaphase, leading to the recruitment of Polo-like kinase 1 (Plk1) to vimentin. Upon binding to Phospho-Ser55 of vimentin, Plk1 is activated, and then phosphorylates vimentin-Ser82. During cytokinesis, Rho-kinase and Aurora-B specifically phosphorylate IF at the cleavage furrow. IF phosphorylation by Cdk1, Plk1, Rho-kinase and Aurora-B plays an important role in the local IF breakdown, and is essential for the efficient segregation of IF networks into daughter cells. As another part of our research on IF, we have set out to find the binding partners with simple epithelial keratin 8/18. We identified tumor necrosis factor receptor type 1-associated death domain protein (TRADD) as a keratin 18-binding protein. Together with data from other laboratories, it is proposed that simple epithelial keratins may play a role in modulating the response to some apoptotic signals. Elucidation of the precise molecular functions of IF is expected to improve our understanding of tumor development, invasion and metastasis. (Cancer Sci 2006; 97: 167,174) [source] Technoreview: Focusing light on infection in four dimensionsCELLULAR MICROBIOLOGY, Issue 4 2004Pascal Roux Summary The fusion of cell biology with microbiology has bred a new discipline, cellular microbiology, in which the primary aim is to understand host,pathogen interactions at a tissue, cellular and molecular level. In this context, we require techniques allowing us to probe infection in situ and extrapolate quantitative information on its spatiotemporal dynamics. To these ends, fluorescent light-based imaging techniques offer a powerful tool, and the state-of-the-art is defined by paradigms using so-called multidimensional (multi-D) imaging microscopy. Multi-D imaging aims to visualize and quantify biological events through time and space and, more specifically, refers to combinations of: three (3D, volume), four (4D, time) and five (5D, multiwavelength)-dimensional recordings. Successful multi-D imaging depends upon understanding the available technologies and their limitations. This is especially true in the field of microbiology where visualization of infectious/pathogenic activities inside living host systems presents particular technical challenges. Thus, as multi-D imaging rapidly becomes a common bench tool to the cellular microbiologist, this review provides the new user with some of the necessary technical insight required to get the best from these methods. [source] | |||||||||||||