Showing papers by "Helmholtz Centre for Environmental Research - UFZ published in 1970"

Reurbanisation in Postsocialist Europe – A Comparative View of Eastern Germany, Poland, and the Czech Republic

Abstract: Since the 1990s, reurbanisation has become an increasingly frequent trajectory for urban development. Many formerly shrinking cities have been able to stabilise their population or even see new growth. Especially prominent in regions like Germany and the UK, but also observed across the whole continent, a lively debate on reurbanisation has developed as a reality of today’s, and a potential trajectory for tomorrow’s, cities in Europe. Postsocialist Europe has not so far been central in the reurbanisation debate, either empirically or theoretically. Subsequently, the postsocialist experience is missing in the discourse and the existing body of evidence. There is, however, some evidence that Czech and Polish cities are also seeing signs of new inner-city growth and a trend towards core city stabilisation. Against this background, the paper scrutinises the issues of reurbanisation and new growth after the shrinking of postsocialist cities. The paper uses the approach of a contrastive comparison between cities in eastern Germany, where reurbanisation has developed as the predominant trajectory for many large cities, and for cities in Poland and the Czech Republic, where this trend is considerably less prominent. It analyses the development of reurbanisation in these cities and their urban regions over the last few decades, its characteristics and the determinants triggering or impeding it. The paper includes data on a national scale as well as from relevant case studies of cities and their urban regions. It argues, among other things, that there is no “postsocialist model” with regard to influencing factors for reurbanisation. Eastern Germany, due to its specific postsocialist situation and transformation trajectory, can be viewed as an “outlier” or “hybrid” which exhibits characteristics typical of postsocialist and western welfare contexts and which is seeing especially dynamic reurbanisation after a phase of extreme shrinkage. Although there are clear signs of inner-city reurbanisation in Polish and Czech cities as well, it seems relatively unlikely that this process will reach the same high levels as in East German cities within the coming years. * This article belongs to a special issue on reurbanisation.

Spatial Aspects Of Grazing In Savanna Rangelands- A Modelling Study Of Vegetation Dynamics

Abstract: Increasing shrub cover density poses a widespread problem in semiarid savanna rangelands. Recently, vegetation dynamics has been studied with the aid of spatially explicit models, aiming to highlight the response of shrub cover to livestock grazing. Assuming that on a local scale, grazing and trampling act as a disturbance ultimately facilitating local extinction, small scale local variability of grazing intensity might influence density and vegetation cover of forage plants and thus affect shrub cover dynamics. We used a spatially explicit grid based simulation model based on southern Kalahari ecology. Plant life histories were modelled at the level of the three major life forms: perennial grasses and herbs, shrubs, annuals. To study the role of small scale local variability of grazing intensity under various levels of livestock grazing pressure we conducted factorial simulation experiments for two large scale grazing patterns: firstly, assuming homogenous grazing, secondly, assuming a grazing gradient as observed around artificial watering points. Our results confirm the previously reported threshold behavior of shrub encroachment, with threshold levels close to the recommended stocking rates of the study area. Stocking rate threshold levels and rates of shrub encroachment were sensitive to small scale local variability of grazing pressure. For grazing regimes with lower local grazing variability, threshold levels of shrub encroachment shifted towards higher grazing pressures, and at given critical stocking rates, shrub encroachment was slower than for grazing regimes with larger local variability. Equally, for grazing regimes with lower local grazing variability, piosphere formation around boreholes required higher grazing pressures, and was slower at given critical stocking rates than for grazing regimes with larger local variability. We conclude that information on small scale spatial variability of grazing intensity is crucial for correct assessment of the impact of livestock grazing on vegetation dynamics in savanna rangelands.

Biomarkers Of The Effect Of VOC Exposure: Recent Developments

Abstract: Biomarkers are convenient tools to characterize 1) specific human exposure to air pollution, 2) responses of the human organism to exposure, and 3) individual variations of both exposure and response. This paper presents two effect monitoring tests as recent examples to study human responses to exposure and the application of the tests in environmental . epidemiology. The common feature of these test methods is the use of the stable isotope tracer technique as a basic working principle. One of the methods, the in vivo [ N]methacetin liver function test, has already been approved for use on humans to characterize SO] load effects on the detoxification capacity of the liver. Its application field has now been extended for use in regions with other air pollution situations such as airborne dust loaded with heavy metals and airborne volatile organic compounds (VOCs). An excellent correlation was seen between dust or SO: load and liver detoxification capacities. The other method, a new in vitro test system has been developed to characterize the early effects of a VOC as an airborne pollutant on the nitrogen metabolism. Using the cell system Tetrahymena pyriformis and the amino acid [ N]arginine as a nutrient in the culture medium, the impact of a toluene load can be measured in terms of changes in the ratios and in the N levels of the various metabolites in several pools. Transactions on Ecology and the Environment vol 29 © 1999 WIT Press, www.witpress.com, ISSN 1743-3541

Simulated Shrubland Ecosystem Dynamics In TheSemi-arid Karoo, South Africa

Abstract: In arid regions, the effects of grazing or sparing management on natural communities of long-lived plants generally take decades to become evident. Event driven dynamic behaviour, unpredictable and low rainfall and complicated interactions between species make it difficult to gather sufficient understanding of plant community dynamics to be able to develop guidelines for sustainable management. To gain a better understanding of the main processes and mechanisms involved in vegetation change, we have developed a spatially explicit individual based model that simulates changes in plant communities over long time spans. The specific aim of the model is to identify key processes of vegetation change and to calculate probabilities and timespans for transitions between different vegetation states. The model shows that the dynamics of the shrub community are typified by episodic and discontinuous changes in species composition with intervening quasi-stable phases lasting some decades. The short-term community dynamics (years to decades) are very sensitive to the sequence of rainfall events. In all simulation experiments the final vegetation state varied by more than 37% after a 60 year simulation period. However, time-scale for changes of the dynamic state of the system are long compared with human lifespans. Simulating resting of an overgrazed part of the shrub community indicated that little improvement in rangeland condition was likely during a period of 60 years. Overgrazing of a rangeland in good initial condition, simulated by reducing seed production in preferred forage plant species, only became obvious 40 or 50 years after the initiation of heavy grazing, and after 70 years the mean vegetation state eventually reached that of an overgrazed rangeland. Transactions on Ecology and the Environment vol 16, © 1997 WIT Press, www.witpress.com, ISSN 1743-3541