Räumlich differenzierende Berechnung großmaßstäblicher Erosionsprognosekarten - Modellgrundlagen der dABAG

A Spatially Differenciating Method for Computing High Resolution Maps of Soil Loss by Rain Wash - Fundamental Principles of the dUSLE The theoretical basis of a procedure to compute maps of the soil loss is presented. This procedure allows to estimate soil loss on a large scale (1:5000) for planning specific protection measures. The procedure uses the Universal Soil Loss Equation combined with a digital terrain model that consists of a triangulated, irregular network. In this way not only slope but also the influence of increasing soil loss down slope and the slope morphology are taken into account. Also, slope morphology is considered along the slope as well as across the slope. Therefore the procedure is called differentiating Universal Soil Loss Equation dUSLE. With the dUSLE it is possible to combine high resolution with high automatisation and reasonable computation time. The application of the USLE has the advantage of easy use and availability of data. Furthermore, most parts of the USLE have been adapted to and verified for German conditions in recent years. In part 2 the integration of the equations presented in the digital terrain model will be described. In a third part the application of the dUSLE in land reconsolidation and farmers extension service will be presented.     

Response of primary plant metabolism to the N-source

Even when plant growth was not visibly affected, ammonium versus nitrate nutrition had distinct effects on some parts of plant metabolism. Barley seedlings growing on 3 mM ammonium rapidly accumulated ammonium up to 20 mM in the roots. In leaves, ammonium accumulation was observed only when the pH of the nutrient medium was very low (pH 4). Yet even under the most extreme conditions there was no indication that plants were suffering from uncoupling of ATP synthesis or from a lack of carbohydrates. Especially dramatic was the response of the organic acid content of pea and barley leaves: it decreased strongly within a few days upon transfer of plants from nitrate to ammonium-media, and this was apparently not due to an inhibition of PEPcarboxylase, which was rather activated under ammonium nutrition. As malate dispappeared from leaves even when pea plants were transferred to an N-free medium, malate degradation was not necessarily connected to increased amino acid synthesis, but eventually to a more rapid decarboxylation by malic enzyme. Also, malate degradation was not a response to ammonium, but rather to (the absence of) nitrate.     

A Novel Particle Contact Assay with the Yeast Saccharomyces cerevisiae (8 pp)

Goal, Scope and Background   Numerous xenobiotics released into surface waters are transferred to suspended particulate matter and finally attached to sediments. Aquatic organisms may be exposed to them by direct particle feeding, by physical contact with contaminated surfaces as an exposure route, and by the uptake of dissolved contaminants after equilibration via the free water phase. In order to assess potential sediment toxicity, each of these exposure routes has to be addressed. This paper presents a newly developed particle contact assay that uses the fermentation performance of a specific Saccharomyces cerevisiae strain for the assessment of toxic effects in sediments. The test procedure is based on the characteristic feature of growing yeast cells to attach to sediment particles, which are also relevant for the accumulation of contaminants. The physical contact with lipophilic contaminants mirrors an exposition pathway for the direct uptake into the cells. In order to quantitatively characterize the toxic effects of particle attached pollutants on the fermentation performance, unpolluted native reference sediment was spiked with representatives for widely distributed anthropogenic contaminants. Methods   Saccharomyces cerevisiae was established as sensitive eukaryotic microorganism for the ecotoxicological assessment of particle attached anthropogenic contaminants in freshwater sediments. For this purpose, yeast cells were cultivated in sediment samples and the resulting fermentation performance was continuously measured. Sediments artifically spiked with HCB, PCB, g-HCH, DDT, and benzo(a)pyrene and solutions of each contaminant were comparatively investigated by means of their adverse effects on yeast fermentation performance. Additionally, four native river sediments characterized by increasing levels of pollution were assessed by the yeast particle contact assay, and simultaneously by standard aquatic tests with algae, daphniae, and luminescent bacteria using pore water and elutriates. Results of the bioassays were related to specific sediment contamination with respect to metals and organic priority pollutants. Results and Discussion   In sediments spiked with PCB and benzo(a)pyrene fermentation, performance was affected extensively below concentrations inhibiting fermentation in contaminant solutions. This suggests a high efficiency of the exposure route by physical contact. The fermentation performance was only slightly affected by single lipophilic pollutants, whereas mixtures of individually spiked sediments caused critically reduced fermentation performance suggesting additive synergistic effects. Native river sediments modestly to critically polluted by hazardous organic compounds lead to a slightly to dangerously reduced fermentation performance in the yeast contact assay. These inhibitory effects were much less pronounced in the standard bioassays conducted with algae, daphniae and luminescent bacteria, applying pore waters and elutriates as sample matrices. Using pore water, inhibition was measured only in the most polluted sediment, elutriates lead to a slight inhibition of the algal growth in the undiluted sample only. These results indicate an improved sensitivity of the yeast particle contact assay compared to the standard assays, due to uptake and physical cell contact as additional routes of exposure. Conclusion   The yeast particle contact assay is a valuable tool for the assessment of ecotoxicological potential in freshwater sediments. Since the assay addresses physical contact as an exposure route, it indicates bioavailability of lipophilic compounds in sediments. Outlook   The sensitive indication of bioavailable contaminants associated to sediment particles by the newly developed yeast particle contact assay recommends it as a complementary microbial bioassay in a test battery for assessing major pathways of contaminants in whole sediments.     

Libri Novi

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Numbers of gastrointestinal helminth eggs of Wyoming cattle in two surveys: 1957 to 1961 and 1973 to 1977

From 1973 to 1977, a survey of internal parasites in Wyoming cattle was conducted via fecal analyses of 1,490 beef cattle. Sugar flotation techniques were used, with a factor of 2 times the actual egg counts. The prevalence of internal parasites of beef cattle in this survey was compared with that in a previous survey conducted on Wyoming beef cattle from 1957 to 1961. Results of analyses indicated no true change in mean eggs per gram of feces (epg) as follows: calves, 14 epg in 1961 and 20 epg in 1977; yearlings, 29 epg in 1961 and 19 epg in 1977; and adults, 22 epg in 1961 and 21 epg in 1977.