Showing papers by "Helmholtz Centre for Environmental Research - UFZ published in 1998"

Assessing the risk of extinction for the brown bear (ursus arctos) in the cordillera cantabrica, spain

Abstract: The status of the brown bear (Ursus arctos) in Spain has suffered a dramatic decline during the last centuries, both in area and numbers. Current relict populations are suspected to be under immediate risk of extinction. The aim of our model is to attain an understanding of the main processes and mechanisms determining population dynamics in the Cordillera Cantabrica. We compile the knowledge available about brown bears in the Cordillera Cantabrica, northern Spain, and perform a population viability analysis (PVA) to diagnose the current state of the population and to support current management. The specially constructed simulation model, based on long-term field investigations on the western brown bear population in the Cordillera Cantabrica, includes detailed life history data and information on environmental variations in food abundance. The method of individual-based modeling is employed to simulate the fate of individual bears. Reproduction, family breakup, and mortalities are modeled in annual time ...

Modelling the impact of small-scale heterogeneities on tree—grass coexistence in semi-arid savannas

Abstract: Summary 1 Savanna ecosystems show codoininaiice of trees and grasses, and the mechanisms involved in their coexisteiice remain unresolved. We investigated the possible influence of small-scale heterogeneities and disturbances in deterniining tree spacing and treegrass coexistence in semi-arid savannas, using a spatially explicit, grid-based siinulation model. 2 We added factors such as seed clumping, locally improved moisture conditions, vegetation clearing and colnbinatiolls of all three of these variables to a previously published model. We also exaillined the influence of changing the size and spatiotemporal correlation aillong individual heterogeneities. 3 Increased seed availability in localized clumps, especially in combination with the other heterogeneity types, had the strongest impact on the long-term tree-grass coexisteiice in the model. Localized deposition of tree seeds in herbivore dung and underground seed caches built by seed-collecting rodents may act as a determinant of the distribution of trees in savannas. 4 Spatially autocorrelated small-scale heterogeneities led to a more stable coexistence of trees and grasses than uiicorrelated heterogeneities did, and at high levels of autocorrelation runs with all three variables led to long-term coexistence in up to 60% of the rainfall scenarios tested. 5 The size of individual heterogeneities also played a significant role in determining whether trees would establish as lone individuals or in clumps. In simulations that included small-scale heterogeneities, the number of isolated trees scattered throughout the landscape increased, whereas large heterogeneity patches and high spatiotemporal autocorrelation tended to promote tree clustering. 6 Simulations based on rainfall data from the southern Kalahari produced a realistic density and spatial distribution for trees in this semi-arid savanna for a realistic range of small-scale heterogeneities. 7 Small-scale disturbances and heterogeneities, at least those that furnish better establishment conditions for tree seedlings, therefore act to increase the range of environmental conditions under which trees and grasses can coexist as savanna. Kej)~>orn's: coexistence, grid-based silnulation model, Kalahari, savanna, seed clumping, spatial vegetation dynamics, stability, tree spacing

Reconciling classical and individual-based approaches in theoretical population ecology: a protocol for extracting population parameters from individual-based models.

Abstract: The two main approaches in theoretical population cific competition. Classical models had, however, only ecology—the classical approach using differential equations and the approach using individual-based modeling—seem to be in- limited success in making ecology more predictive. They compatible. Linked to these two approaches are two different have produced understanding in the sense of possible ex- timescales: population dynamics and behavior or physiology. planations of observed phenomena, but the model pre- Thus, the question of the relationship between classical and indi- dictions are not testable as a rule, and therefore, classical vidual-based approaches is related to the question of the mutual population models do not directly contribute to the sci- relationship between processes on the population and the behav- entific cycle of hypotheses, predictions, and testing ioral timescales. We present a simple protocol that allows the two (Grimm 1994). One reason for this could be that the

Natural and Anthropogenic Sulfuric Acidification of Lakes

Abstract: Since the early 1960s, acid rain has affected surface waters in regions with soils low in carbonates. The acidification of whole lake districts resulted from industrial emissions distributed through the atmosphere on a regional scale. A large body of literature exists about this acidification of surface waters by acid rain, its ecological consequences, and countermeasures to restore landscape and waters (e.g., Drablos and Tollan 1980; Fleischer 1993; Steinberg and Wright 1994; Stumm 1995). The hydrochemistry and the ecological consequences were extensively described (e.g., Dillon et al. 1984), leaving the impression that all acidic lakes are anthropogenic and artificial waters that principally need to be restored, for instance by liming measures (Henrikson and Brodin 1995).

Population dynamics, disturbance, and pattern evolution: identifying the fundamental scales of organization in a model ecosystem.

Abstract: We used auto‐ and cross‐correlation analysis and Ripley's K‐function analysis to analyze spatiotemporal pattern evolution in a spatially explicit simulation model of a semiarid shrubland (Karoo, South Africa) and to determine the impact of small‐scale disturbances on system dynamics. Without disturnities bance, local dynamics were driven by a pattern of cyclic succession, where ‘colonizer’ and ‘successor’ species alternately replaced each other. This results in a strong pattern of negative correlation in the temporal distribution of colonizer and successor species. As disturbance rates were increased, the relationship shifted from being negatively correlated in time to being positively correlated—the dynamics became decoupled from the ecologically driven cyclic succession and were increasingly influenced by abiotic factors (e.g., rainfall events). Further analysis of the spatial relationships among colonizer and successor species showed that, without disturbance, periods of attraction and repulsi...

Extraction of microorganisms from soil: evaluation of the efficiency by counting methods and activity measurements

Abstract: Different procedures for the release of microorganisms from soils were tested. The extraction efficiency was evaluated by combining biochemical activities (fluorescein diacetate hydrolysis, dehydrogenase activity and dimethylsulfoxide reduction) and cell counting. In contrast to the counting methods these activities have the advantage that there is no interference from the soil matrix or from the clay and silt in the extracts. We determined the distribution of activities and cell counts among the successive extracts and the soil residue of a three-step and a five-step extraction procedure. Centrifugation at 600×g, used in order to separate soil particles, causes a significant proportion of the bacteria and nearly all fungi to enter the sediment. The influence of relative centrifugal forces

Chemical Characteristics of Water and Sediment in Acid Mining Lakes of the Lusatian Lignite District

Abstract: Hard and brown coal mining has a long tradition in central and eastern Europe and covers large areas of mining in Germany, Poland and the Czech Republic (Geller et al., this Vol.). In Germany there are three main districts of lignite surface mining: the Rheinish district near Cologne, the mid-German district around Leipzig and the Lusatian district around Cottbus in the most eastern part of Germany. Surface mining of lignite (brown coal) results in several environmental problems, for example important disturbances of the natural water balance, mass transfer of billions of tons of soil and devastation of nature. Among these, water acidification is an already well-known effect. Sulphide minerals, such as pyrite and marcasite, are commonly associated with coal and most metal ores. Weathering and oxidation of these minerals take place in the host rocks and substrates of the lignite horizons when they are exposed to air. The release of the oxidation products, mainly acidity, iron and sulphate, is known as acid mine drainage (AMD) and has been the subject of intense research for decades (e. g. Singer and Stumm 1970; Lowsen 1982; Nordstrom 1982; van Berk 1987; Morrison et al. 1990; Blowes et al. 1991, Hedin et al. 1994; Wisotzky 1994).

Degradation of various chlorophenols under alkaline conditions by Gram‐negative bacteria closely related to Ochrobactrum anthropi

Abstract: From concrete debris of a demolished herbicide production plant several Gram-negative bacterial strains were isolated, which exhibit metabolic capabilities for the degradation of 2,4-dichlorophenol (DCP), 4-chloro-2-methylphenol (MCP) and 4-chlorophenol (4-CP), while 2-chlorophenol (2-CP) was degraded at a slower rate. Degradative activity was inducible and was impeded by adding of 100 mg/l of chloramphenicol to growing cultures. The strains displayed alkaliphilic properties with optimum DCP/MCP degradation at pH values around 8.5—9.5; activity was observed up to pH values of 11. Degradation was most likely complete according to chlorine balances; formation of intermediary products was observed with MCP some time. Specific activity of up to 380 μmol/h · g dry mass was found within the concentration range of 10—20 mg/l DCP; higher concentrations retarded the activity with complete inhibition at 200—400 mg/l. Some of the strains carry plasmids whose presence was not unambiguously correlated to the degradative properties. Ribotyping revealed a high degree of relationship between the strains. Preliminary taxonomic investigations showed close rela-tionship to Ochrobactrum anthropi.

Etherolytic cleavage of 4-(2,4-dichlorophenoxy)butyric acid and 4-(4-chloro-2-methylphenoxy)butyric acid by species of Rhodococcus and Aureobacterium isolated from an alkaline environment.

Abstract: Bacterial strains were isolated from the concrete rubble of a demolished herbicide production plant. The predominant feature of these strains was the etherolytic cleavage of 4-(2,4-dichlorophenoxy)butyric acid (DCPB)1) and 4-(4-chloro-2-methylphenoxy)butyric acid (MCPB) while liberating 2,4-dichlorophenol (DCP) and 4-chloro-2-methylphenol (MCP) respectively. Some of the isolates were identified by 16S rDNA sequence analysis and shown to belong to the genera Aureobacterium sp. (strain K2-17) and Rhodococcus (Rh. erythropolis K2-12). The other strains isolated clustered into these two groups according to fatty acid analysis. Etherolytic cleavage proceeded under neutral to alkaline conditions with an optimum at around pH 8.5. With Aureobacterium sp. No. K2-17, the degradation rate was zero at a pH of 6 but as much as 60% of the maximum activity was observed at pH 10.5. With Rh. erythropolis K2-12, by contrast, pronounced activity was detected at pH 6.5 while degradation was no longer observed at pH 10.5. The maximum rates of cleavage were about 1 mmol DCPB/h.g dry mass with Aureobacterium sp. No. K2-17 and about 0.6 mmol DCPB/h.g dry mass with Rh. erythropolis K2-12. DCPB and MCPB were utilized to the same extent. Substrate cleavage and product formation (DCP) proceeded at almost equal rates with Aureobacterium sp. No. K2-17 and Rh. erythropolis K2-12, which indicates that this compound was not further metabolized. Only phenoxybutyric acid compounds served as substrates; phenoxyacetic acid and phenoxypropionic acid derivatives were not utilized by these strains.

Environmental Quality Targets for Urban Structural Units in Leipzig with a View to Sustainable Urban Development

Abstract: The redevelopment process taking place in east German cities since the reunification of Germany presents a unique chance for the integration of aspects of sustainable urban development into the transformation process from the beginning. Unfortunately, while cities are being radically reshaped, development patterns from western cities are being copied and ecologically comprehensive approaches are often not being taken into account.

Sustainable farming at the edge of the Namib: analysis of land use strategies by a computer simulation model.

Abstract: The farm Gamis is located about 250 km SW from Windhoek at the edge of the Namib. Mean annual precipitation is 177 mm with enormous fluctuations in space and time. Extensive pastoral agriculture is supposed to be the appropriate type of land use in this ecologically sensitive region where much of the land is now degraded due to overgrazing in the past. At the Gamis farm, Karakul sheep are kept for the production of furs. The farmland (30000 ha) is divided into 98 paddocks, approximately 60 of them are used for the grazing of (up to three) fur production flocks. A sophisticated grazing rotation system has prevented the land from degradation, at the same time guaranteeing the farm's economic survival. We regard this management strategy as an example of sustainable land use. Our computer simulation model is constructed in order to understand the basis of this strategy's success and to apply this knowledge to other situations. The model is a top-down approach that simulates rainfall and development of the vegetation according to long-term observations by the farmer. Rules of the rotation system have been included in the model. Variations of the rules are analysed to compare different strategies. Model results show that the farmer's strategy is able to cope with aridity in general and particularly with the typical occurence of periods of drought to be found in this region. Alternative strategies are found to be less successful. 1 The karakul farm Gamis Wide regions in southern Africa are exposed to extreme weather conditions with high fluctuations of rainfall in space and time. Food availability for herbivores is unpredictable because growth of plants and rainfall are strongly Transactions on Ecology and the Environment vol 16, © 1997 WIT Press, www.witpress.com, ISSN 1743-3541

Growth forms of annual vascular plants in central Europe

Abstract: The investigation of the vegetative characters of annual species from central Europe showed a hitherto not regarded large spectrum of 20 growth forms within this plant group. These growth forms can be identified by means of a dichotomous key. This is also a new method to present growth form systems. Although several surveys about growth forms have been carried out, the proposed systems are either incomplete or not consequent in the use of their classifying criteria. Moreover, annual species have never been investigated systematically according to their growth forms. Important characters which were used to characterize growth forms are the occurrence of a rosette, the presence or absence of supporting tissue which causes aerostability or aerolability, succulence, growth direction (plagiotropous, orthotropous) and metamorphoses (for scrambling). According to the mode of surviving the resting period, annuals can be grouped into therophytes, hydrophytes, and hemicryptophytes. Whereas therophytic and hydrophytic annuals perennate the winter exclusively as generative diaspores (seeds, spores), hemicryptophytic species survive as seedlings or young plants.

Permeable Pavements — an Appropriate Method to Reduce Stormwater Flow in Urban Sewer Systems?

Abstract: Impervious surfaces are of great environmental concern because of their disturbing influence on soil properties. The soil destruction has various consequences for the ecosphere. Impervious surfaces reduce the soil water content and the infiltration and storage capacity of the soil, as well as evapotranspiration. Therefore careful handling of all soil aspects is an important part of environmental protection. On the other hand, a sealed area causes accelerated runoff with higher peak rates thus the sealing of surfaces is a decisive factor in the design and construction of urban sewerage systems. Due to the lack of reliable data on the infiltration and runoff rates of permeable paved areas, an investigation of the permeability of different pavements was carried out in 1994, supported by the Department for Environment and Geology of Saxony.

Photodecomposition of 4-amino-1,2,4-triazin-3,5-diones and -thiones in oxygenated aqueous solutions

Abstract: The photodecomposition of newly synthesized 4-amino-1,2,4-triazinthione 1 and -dione 2 was examined in oxygenated aqueous solutions at various pH values. The degradation pathway of these compounds was compared with the photochemical decomposition of the herbicide metribuzin. Side-chain degradation by deamination, decarboxylation, sulfoxidation and dealkylation is typical for photolysis. Structurally similar compounds display substantial differences with respect to degradation. The pH value has an accelerating or inhibiting effect on the degradation rate. After the rapid formation of basic metabolites by the deamination of 1 and the decarboxylation of 2, selective decomposition takes place in alkaline and acidic solutions, whereas a non-selective course was detected under neutral conditions. The radicalic mechanisms of important reaction steps are discussed. Several metabolites with intact heterocyclic ring systems were identified as photochemically stable final products by the addition of a standard compound, such as 6-azauracile or 6-azathymine. In contrast to side-chain degradation, ring cleavage was only observed after long irradiation times. Carboxylic and ketocarboxylic acids as well as some inorganic ions were identified in the irradiated solution as the degradation products of side-chain degradation and ring cleavage.

Morphology and anatomy in annual taxa of Beta vulgaris s.l. (Chenopodiaceae)

Abstract: Beta vulgaris s.l. is a morphologically variable taxon, that has transitional growth types between strictly orthotropous and plagiotropous growth. The development of a “secondary branching system” at the end of the growing season in taxa that are summer annual (under the climatic conditions of Central Germany) leads to perennial taxa that form slender storage roots and overwinter as rosettes. The shoots of the four morphologically different annual taxa are very similar anatomically. Collenchymatous ridges, that are conspicuous macroscopically as stem ridges, are typical. The secondary growth is anomalous and often irregular. Six more or less complete rings of connective and vascular tissue are formed in the roots by successively arising cambia, which have an unlimited ability to divide. However, the diameter of the roots does not only enlarge by divisions within the cambia but also by primary growth within the connective tissue.

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.

Can near infrared-absorption spectra explain the different diffusivities of substituted benzenes and alcohols in octan-1-ol?

Abstract: The considerable diffusivity difference of substituted benzenes and of alcohols in octan-1-ol1 suggests a strong influence of specific solute-solvent interactions (hydrogen bonding). For the quantification of these effects we dried to detect correlations between the diffusion coefficients in octan-1-ol and the near infrared (NIR)-spectra of the solutions. In our study we chose four aliphatic alcohols, benzene, phenol and seven substituted benzenes. By means of different methods of multivariate analysis (PCR, PLS) we tested the possibilities of the classification and prediction of diffusion coefficients using NIR-spectra. From the preliminary results and under the usual assumption that NIR spectra refer to specific solute–solvent interactions it can be concluded that these interactions also play an important role in the diffusive transport mechanism in liquid octan-1-ol.

Goals and Measures of Nature Conservation and Landscape Protection in Urban Cultural Landscapes of Central Europe — Examples from Leipzig

Abstract: Over three quarters of the European population live in urban areas. This living space directly moulds the relationship of many people to their environment. Nature conservation and landscape protection in the urban cultural landscape are not only of great importance, but also require a modified approach which clearly differentiates itself from the protection of rural landscapes (Breuste 1995).

Social Atlas of Leipzig

Abstract: The Social Atlas of Leipzig is the first atlas which considers the social and urban ecological structural changes in a large east German city after the unification of the two German States in 1990. It is an instrument for the sociological analysis and evaluation of urban development. The main objectives are as follows: 1. spatial registration, cartographic representation and assessment of these social consequences that accompany the abrupt transition from the centrally managed economy in the former GDR to the free market economy in an urban frame; 2. description of the social-spatial differentiation of residential areas by means of selected social, political and economic factors including the actual land use, as well as structural, infrastructural and environmental characteristics; 3. characterisation of the actual social situation in the city of Leipzig by registering the social conditions and their changes in time, their cartographic registration and interpretation.