Simulating forest succession after blowdown events: The crucial role of space for a realistic management

Ecological patterns vary in space and time. Therefore, when using dynamic models in ecology, the spatial aspect should not be neglected prematurely since it could possibly change the model outcomes to a considerable extent. In view of this problem, we describe here a method how to construct a non-spatial version from a spatially explicit simulation model. The principle idea is to suppress the spatial correlations of cells in a grid in time by continuously re-assigning a random neighbourhood for each cell on the grid. Since this procedure actually eliminates the spatial dimensions, it allows to quantify the unadulterated impact of spatial processes on the model results. To illustrate an important application of this approach in the context of forest management we use a grid-based model that simulates succession of Norway spruce (Picea abies (L.) Karst.) at mountainous sites after blowdown events. The output of this model is compared with the results of the deduced non-spatial version of this model regarding the predicted amount of re-growing trees. The non-spatial version dramatically overestimates the number of spruce trees on different microsites. Thus, the uncritical use of the non-spatial model might give reason to wrong management decisions that are based on too optimistic predictions. In practice, this may lead to dangerous situations, especially in mountain forests serving as protection against avalanches and landslides. This example demonstrates the successful applicability of our approach. Our method can be interpreted as a contribution to an extended sensitivity analysis: it analyses the sensitivity of the results due to structural changes of the model. This sensitivity allows one to estimate the redundancy or the necessity of spatially explicit processes in a model with regard to the parsimony principle of modelling. Since our approach is not dependent on special features of the simulation model used here, it is assumed to be applicable for other spatial models, too, and can thus be considered of general interest for a diligent model analysis.     

Combined integral and particle model for describing the dispersion,dilution, terminal layer formation and influence area from a point source discharge into a water body

Contamination of coastal water is a persistent threat to ecosystems around the world. In this study, a novel model for describing the dispersion, dilution, terminal layer formation and influence area from a point source discharge into a water body is presented and compared with field measured data. The model is a Combined Integral and Particle model (CIPMO). In the initial stage, the motion, dispersion and dilution of a buoyant jet are calculated. The output from the buoyant jet model is then coupled with a Lagrangian Advection and Diffusion model describing the far-field. CIPMO ensures that both the near- and far-field processes are adequately resolved. The model either uses empirical data or collects environmental forcing data from open source hydrodynamic models with high spatial and temporal resolution. The method for coupling the near-field buoyant jet and the particle tracking model is described and the output is discussed. The model shows good results when compared with measurements from a field study.

     

Road safety performance indicators and their explanatory value: A critical view based on the experience of Central European countries

Counts of road crashes and their victims represent essential information for road safety practitioners allowing them to analyse their spatial and temporal aspects. However, they cannot provide details on the factors causing road crashes. As a result, various road safety performance indicators (RSPIs) were introduced, making it possible to gather information on the effectiveness of interventions on road safety in given areas. However, analysis of the trends in road casualties in several Central European countries based on safety performance (measured by RSPIs) suggest that not even these indicators can provide full understanding of road safety trends, and, if they are applied generally without the required background information, this could even lead to serious misinterpretation of the trends in road casualties. Sudden breaks in long-term trends seem to be linked to the transition process and to certain legislative reforms. The exposure and socio-economic climate appear to have had a major impact on road crash outcomes. Various additional indicators describing organisational and structural aspects may be helpful, therefore, in better understanding and predicting the development in road safety for individual countries.     

Microbially assisted phytoremediation approaches for two multi-element contaminated sites

Phytoremediation is an environmental friendly, cost-effective technology for a soft restoration of abandoned mine sites. The grasses Agrostis capillaris, Deschampsia flexuosa and Festuca rubra, and the annual herb Helianthus annuus were combined with microbial consortia in pot experiments on multi-metal polluted substrates collected at a former uranium mine near Ronneburg, Germany, and a historic copper mine in Kopparberg, Sweden, to test for phytoextraction versus phytostabilization abilities. Metal uptake into plant biomass was evaluated to identify optimal plant–microbe combinations for each substrate. Metal bioavailability was found to be plant species and element specific, and influenced by the applied bacterial consortia of 10 strains, each isolated from the same soil to which it was applied. H. annuus showed high extraction capacity for several metals on the German soil independent of inoculation. Our study could also show a significant enhancement of extraction for F. rubra and A. capillaris when combined with the bacterial consortium, although usually grasses are considered metal excluder species. On the Swedish mixed substrate, due to its toxicity, with 30 % bark compost, A. capillaris inoculated with the respective consortium was able to extract multi-metal contaminants.     

Desorption kinetics studies on PAH-contaminated soil under varying temperatures

The purpose of this study was to investigate the effect of temperature on the release of polycyclic aromatic hydrocarbons (PAHs) from aged contaminated soil. The release of fluorene, phenanthrene, anthracene, fluoranthene and pyrene at 7, 15, 18 and 23 degrees C was studied using a column leaching method with a hydraulic retention time of 0.5 h. As the temperature declined from 23 to 7 degrees C the concentrations decreased by a factor of 11-12 for all the studied compounds except for anthracene, which only decreased by a factor 7. Rate constants at maximum release rate at the four studied temperatures were assessed. From temperature dependence studies, apparent activation energies of desorption, E*(des), were calculated. E*(des)-values appeared to be in the range of 105-137 kJ mol(-1) for the studied PAHs and increased with the LeBas molar volume of the compounds. The increase of E*(des) with increased molecular size indicates stronger sorption with increased hydrophobicity of the compounds.     

Antibiotic resistance,virulence factors and biofilm formation ability in Escherichia coli strains isolated from chicken meat and wildlife in the Czech Republic

Attachment of pathogenic bacteria to food contact surfaces and the subsequent biofilm formation represent a serious threat for the food industry, since these bacteria are more resistant to antimicrobials or possess more virulence factors. The main aim of this study was to investigate the correlation between antibiotic resistance against 13 antibiotics, distribution of 10 virulence factors and biofilm formation in 105 Escherichia coli strains according to their origin. The high prevalence of antibiotic resistance that we have found in wildlife isolates could be acquired by horizontal transfer of resistance genes from human or domestic or farm animals. Consequently, these commensal bacteria might serve as indicator of antimicrobial usage for human and veterinary purposes in the Czech Republic. Further, 46 out of 66 resistant isolates (70%) were able to form biofilm and we found out statistically significant correlation between prevalence of antibiotic resistance and biofilm formation ability. The highest prevalence of antibiotic resistance was observed in weak biofilm producers. Biofilm formation was not statistically associated with any virulence determinant. However, we confirmed the correlation between prevalence of virulence factors and host origin. Chicken isolates possessed more virulence factors (66%), than isolates from wildlife (37%). We can conclude that the potential spread of antibiotic resistance pattern via the food chain is of high concern for public health. Even more, alarming is that E. coli isolates remain pathogenic potential with ability to form biofilm and these bacteria may persist during food processing and consequently lead to greater risks of food contamination.