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  • Artikel  (38)
  • Triticum aestivum
  • fish
  • stability
  • Springer  (38)
  • Geologie und Paläontologie  (38)
  • 1
    Digitale Medien
    Digitale Medien
    Discrete stability of the Differential System Method evaluated with geostatistical techniques (1998)
    Springer
    Stochastic environmental research and risk assessment 12 (1998), S. 191-204 
    Details
    ISSN: 1436-3259
    Schlagwort(e): Keywords: groundwater flow ; inverse problems ; stability ; geostatistical interpolation ; kriging.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik , Geographie , Geologie und Paläontologie
    Notizen: Abstract The Differential System Method (DSM) permits identification of the physical parameters of finite-difference groundwater flow models in a confined aquifer when piezometric head and source terms are known at each point of the finite-difference lattice for at least two independent flow situations for which the hydraulic gradients are not parallel. Since piezometric head data are usually few and sparse, interpolation of the measured data onto a regular grid can be performed with geostatistical techniques. We apply kriging to the sparse data of a synthetic aquifer to evaluate the stability of the DSM with respect to uncorrelated measurement errors and interpolation errors. The numerical results show that the DSM is stable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004770050017
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  • 2
    Digitale Medien
    Digitale Medien
    Preparation of nitrogen and phosphorus-enriched paddy straw compost and its effect on yield and nutrient uptake by wheat (Triticum aestivum L.) (1989)
    Springer
    Biology and fertility of soils 8 (1989), S. 339-342 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Wheat ; Paddy straw compost ; N and P enrichment ; Rock phosphate ; Pyrite ; Triticum aestivum ; Nutrient uptake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary A nutrient-rich compost from paddy straw was prepared using urea and Mussoorie rock phosphate for N and P enrichment respectively. Inorganic N was partly conserved in the compost by the addition of pyrite. Citric-acid-soluble P also increased with the addition of pyrite. Compost containing about 1.6% total N and 3.3% total P was found to be a good source of P for a wheat crop and also supplied a significant amount of N to the plants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00263166
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  • 3
    Digitale Medien
    Digitale Medien
    A reliable method for the selection of axenic seedlings (1990)
    Springer
    Biology and fertility of soils 9 (1990), S. 281-282 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Surface sterilization ; Contaminants ; Sterile plant selection ; Axenic seedlings ; Triticum aestivum ; Trifolium pratense ; Trifolium repens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Sterile seedlings are required for the investigation of interactions between microorganisms and plants. The present study was designed to develop a simple and reliable method for the selection of sterile seedlings by the use of liquid nutrient media, avoiding some of the disadvantages of solid media. The method of germinating surface-sterilized seedlings on solid water agar or nutrient media was compared with our method for sterility control in nutrient broth. Sterile plant selection in liquid media was the most sensitive method for detecting bacterial and fungal contaminants. Sterile plants grow with the same vigour as unsterilized plants and can be used for sterile plant experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00336240
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  • 4
    Digitale Medien
    Digitale Medien
    Interaction of 15N-labelled ammonium nitrate, urea and ammonium sulphate with soil N during growth of wheat (Triticum aestivum L.) under field conditions (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 185-189 
    Details
    ISSN: 1432-0789
    Schlagwort(e): 15N-labelled fertilizer ; Added N interaction Fertilizer N uptake ; Soil N uptake ; Wheat ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effects of 15N-labelled ammonium nitrate, urea and ammonium sulphate on yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L. cv. Mexi-Pak-65) were studied in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 64.0–74.8%, 61.5–64.7% and 61.7–63.4% of the N from ammonium nitrate, urea and ammonium sulphate, respectively. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea and ammonium sulphate. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the three N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied with the method of application of fertilizer N. Ammonium nitrate, urea and ammonium sulphate gave 59.3%, 42.8% and 26.3% more added N interaction, respectively, when applied by the broadcast/worked-in method than with band placement. A highly significant correlation between soil N and grain yield, dry matter and added N interaction showed that soil N was more important than fertilizer N in wheat production. A values were not significantly correlated with added N interaction (r=0.719). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N stood proxy for unlabelled soil N.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00336556
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  • 5
    Digitale Medien
    Digitale Medien
    Phosphatase activity in the rhizosphere and its relation to the depletion of soil organic phosphorus (1987)
    Springer
    Biology and fertility of soils 3 (1987), S. 199-204 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Phosphatases ; Rhizosphere ; Organic phosphorus ; Allium cepa ; Brassica oleracea ; Triticum aestivum ; Trifolium alexandrinum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The distribution of phosphatase activity and of phosphate fractions of the soil in the proximity of roots was studied in order to evaluate the significance of phosphatases in P nutrition of various plants (Brassica oleracea, Allium cepa, Triticum aestivum, Trifolium alexandrinum). A considerable increase in both acid and alkaline phosphatase activity in all the four soil-root interfaces was observed. Maximum distances from the root surface at which activity increases were observed ranged from 2.0 mm to 3.1 mm for acid phosphatase and from 1.2 mm to 1.6 mm for alkaline phosphatase. The increase in phosphatase activity depended upon plant age, plant species and soil type. A significant correlation was noticed between the depletion of organic P and phosphatase activity in the rhizosphere soil of wheat (r = 0.99**) and clover (r = 0.97**). The maximum organic P depletion was 65% in clover and 86% in wheat, which was observed within a distance from the root of 0.8 mm in clover and 1.5 mm in wheat. Both the phosphatases in combination appear to be responsible for the depletion of organic P.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00640630
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  • 6
    Digitale Medien
    Digitale Medien
    Dynamics of CO2 evolution in grey forest soil of the Baikal forest-steppe (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 327-331 
    Details
    ISSN: 1432-0789
    Schlagwort(e): CO2 emission ; Field method ; Soil respiration ; Triticum aestivum ; Soil moisture ; Carbon reservoirs ; Greenhouse effect ; Grey forest soil ; Mineralization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The dynamics of the rate of CO2 evolution from soil in fallow and croplant under spring wheat (Triticum aestivum L.) was studied in a crop rotation in grey forest soil of the Baikal forest-steppe during the growing season and in different years. It was shown that the regional characteristics of soils and hydrothermal conditions in different years affect the rate of CO2 evolution in agroecosystems. The seasonal dynamics of CO2 is characterized by insignificant changes in the autumn to spring period and enhanced emission in hot and dry summers. CO2 evolution is assumed to increase due to enhanced mineralization and partial diffusion from the carbonate horizon at the depth of the seasonal frost. During the growing season the dynamics of CO2 evolution depends on the soil moisture regime. There was a strong correlation between the rate of CO2 emission and soil moisture in the particularly dry year of 1993 (η=0.86) and a moderate correlation in the other years (η=0.38–0.54). The effect of the previous crop and fertilizer application on the rate of CO2 emission was insignificant. In a continuous fallow the total carbon release into the atmosphere varied throughout the years studied from 558 to 1880 kg ha-1. Humus losses varied from 0.9% to 3.1%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00335962
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  • 7
    Digitale Medien
    Digitale Medien
    Carbon transfer in a winter wheat (Triticum aestivum) ecosystem (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 76-82 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Biomass accumulation ; Decomposition ; Litter ; Soil organic matter ; Soil respiration ; 14C deposition ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary In a field experiment with 14C-labeled winter wheat conducted in the north-central region of the United States, crop-accumulated carbon (grain excluded) returned to the soil was found to be 542 g m−2 year−1. Almost half of the carbon from the underground compartment was released in the form of CO2 during the first 3 months after harvest due to very favorable conditions for biological activity. After 18 months, no less than 80% of the carbon from the plant residues was mineralized. About 16% of straw carbon and 24% of root carbon was transferred into soil organic matter. The annual rate of soil organic matter decomposition was approximated as 1.7%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00264350
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  • 8
    Digitale Medien
    Digitale Medien
    Yield response of spring wheat cultivars (Triticum aestivum and T. turgidum) to inoculation with Azospirillum brasilense under field conditions (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 27-35 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Triticum aestivum ; T. turgidum ; Nitrogen fixation ; Field inoculation ; Acetylene reduction assay (ARA)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Eight commercial Israeli spring wheat cultivars (six Triticum aestivum and two T. turgidum) grown with 40 and 120 kg N/ha were tested for responses to inoculation with Azospirillum brasilense. At the low level of N fertilization (40 kg/ha), five cultivars showed significant increases in plant dry weight measured at the milky ripe stage; however, by maturation only the cultivar “Miriam” showed a significant increase in grain yield. Two cultivars, which had shown a positive inoculation effect at the earlier stages, had a significant decrease in grain yield. No significant effect of inoculation was found at the high N level. To confirm those results, four wheat (T. aestivum) cultivars were tested separately over 4 years in 4 different locations under varying N levels. Only Miriam showed a consistently positive effect of Azospirillum inoculation on grain yield. Inoculation increased the number of roots per plant on Miriam compared with uninoculated plants. This effect was found at all N levels. Nutrient (N, P and K) accumulation and number of fertile tillers per unit area were also enhanced by Azospirillum, but these parameters were greatly affected by the level of applied N. It is suggested that the positive response of the spring wheat cultivar “Miriam” to Azospirillum inoculation is due to its capacity to escape water stresses at the end of the growth season.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280347
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  • 9
    Digitale Medien
    Digitale Medien
    Dynamics of CO2 evolution in grey forest soil of the Baikal forest-steppe (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 327-331 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Key words CO2 emission ; Field method ; Soil respiration ; Triticum aestivum ; Soil moisture ; Carbon reservoirs ; Greenhouse effect ; Grey forest soil ; Mineralization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The dynamics of the rate of CO2 evolution from soil in fallow and cropland under spring wheat (Triticum aestivum L.) was studied in a crop rotation in grey forest soil of the Baikal forest-steppe during the growing season and in different years. It was shown that the regional characteristics of soils and hydrothermal conditions in different years affect the rate of CO2 evolution in agroecosystems. The seasonal dynamics of CO2 is characterized by insignificant changes in the autumn to spring period and enhanced emission in hot and dry summers. CO2 evolution is assumed to increase due to enhanced mineralization and partial diffusion from the carbonate horizon at the depth of the seasonal frost. During the growing season the dynamics of CO2 evolution depends on the soil moisture regime. There was a strong correlation between the rate of CO2 emission and soil moisture in the particularly dry year of 1993 (η=0.86) and a moderate correlation in the other years (η=0.38–0.54). The effect of the previous crop and fertilizer application on the rate of CO2 emission was insignificant. In a continuous fallow the total carbon release into the atmosphere varied throughout the years studied from 558 to 1880 kg ha–1. Humus losses varied from 0.9% to 3.1%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00335962
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  • 10
    Digitale Medien
    Digitale Medien
    Inoculation with phosphate-solubilizing microorganisms and a vesicular-arbuscular mycorrhizal fungus improves dry matter yield and nutrient uptake by wheat grown in a sandy soil (1999)
    Springer
    Biology and fertility of soils 28 (1999), S. 139-144 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Key words Phosphate-solubilizing microorganisms ; Mussoorie rock phosphate ; Vesicular-arbuscular mycorrhizae ; Triticum aestivum ; Nutrient-deficient soils
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract  The effect of inoculating wheat (Triticum aestivum L.) with the PO4 3–-solubilizing microorganisms (PSM) Bacillus circulans and Cladosporium herbarum and the vesicular-arbuscular mycorrhizal (VAM) fungus Glomus sp. 88 with or without Mussoorie rock phosphate (MRP) amendment in a nutrient-deficient natural sandy soil was studied. In the sandy soil of low fertility root colonization by VAM fungi was low. Inoculation with Glomus sp. 88 improved root colonization. At maturity, grain and straw yields as well as N and P uptake improved significantly following inoculation with PSM or the VAM fungus. These increases were higher on combined inoculation of PSM and the VAM fungus with MRP amendment. In general, a larger population of PSM was maintained in the rhizosphere of wheat in treatments with VAM fungal inoculation and MRP amendment. The results suggest that combined inoculation with PSM and a VAM fungus along with MRP amendment can improve crop yields in nutrient-deficient soils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003740050475
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  • 11
    Digitale Medien
    Digitale Medien
    Peculiar effect of Azospirillum inoculation on growth and nitrogen balance of winter wheat (Triticum aestivum) (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 55-59 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Azospirillum brasilense ; Triticum aestivum ; Inoculation ; N and dry matter yield ; N percentages in plant parts ; Associative N2 fixation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Wheat plants (Triticum aestivum) grown in pots and in the field under the Mediterranean climate of the south of France were inoculated with a strain of Azospirillum brasilense. Comparisons with non-inoculated plants grown under the same conditions showed significant responses to inoculation with an increase in the number of fertile tillers, shoot and root dry weight, and root to shoot biomass ratio. The roots of inoculated plants attracted relatively more assimilates than those of the control plants until a late stage of growth (heading stage) but the rhizosphere respiration expressed per unit of root growth was not increased by inoculation. Nitrogen yield, both total and in grains, was also enhanced; however, N percentages of all aerial parts of the plants grown in pots were always statistically lower after inoculation than in the control. At maturity, the N % in seeds was 1.81 and 2.45, respectively. The possible mechanisms of this effect of inoculation under the experimental conditions of this study are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280351
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  • 12
    Digitale Medien
    Digitale Medien
    Gram-negative bacterial flora on the root surface of wheat (Triticum aestivum) grown under different soil conditions (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 273-281 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Wheat ; Triticum aestivum ; Rhizosphere ; Soil microflora ; Gram-negative bacteria ; API 20 NE ; Flavobacterium spp ; Cytophaga
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We identified 161 Gram-negative bacterial strains isolated from the root surface of wheat grown under different soil conditions. The strains were divided into seven groups based on major morphological and physiological properties. Taxonomic allocation of the groups was verified by guanine+cytosine contents of DNA. Except for one group, which may be assumed to include bacteria belonging to the genera Flavobacterium and Cytophaga, the various groups were taxonomically united. The distribution of the groups changed with soil improvement. Pseudomonads predominated in unimproved soil, but Flavobacterium and Cytophaga spp. were predominant in the most improved soil. As all the strains were non-fermentative by Hugh and Leifson's test, API 20NE identification was applied. However, many strains were misidentified by this system, especially in the Flavobacterium and Cytophaga spp. group. For ecological studies, the strains were classified to species level by the API 20 NE system and by the results of a combination of guanine+cytosine (mol%) and isoprenoid quinone data. The pattern of distribution of the bacteria on the root surface of wheat varied at species level within one genus depending on soil conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00335955
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  • 13
    Digitale Medien
    Digitale Medien
    Effect of wheat (Triticum aestivum) roots on mineralization rates of soil organic matter (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 67-70 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Root activity ; Soil C mineralization ; 14C-labelled plant material ; Decomposition stages ; Wheat ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Two different soils were amended with 14C-labelled plant material and incubated under controlled laboratory conditions for 2 years. Half the samples were cropped with wheat (Triticum aestivum) 10 times in succession. At flowering, the wheat was harvested and the roots removed from the soil, and a new crop was started. Thus, the soil was continuously occupied by predominantly active root systems. The remaining samples were maintained without plants under the same conditions. The aim of the experiment was to study the effects of active roots on C-mineralization rates during different stages of decomposition and during long-term incubation. During the first 200 days, corresponding to the active decomposition stages, the roots weakly reduced 14C mineralization. With a lower level of decomposition, when more than 60% of the initial 14C was mineralized and when the available nutrients were markedly exhausted by plant uptake, the roots stimulated 14C mineralization.[/ p]
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00260735
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  • 14
    Digitale Medien
    Digitale Medien
    Root activity and carbon metabolism in soils (1988)
    Springer
    Biology and fertility of soils 7 (1988), S. 71-78 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Root activity ; Rhizosphere ; C metabolism ; Microbial biomass ; Microbial activity ; Wheat ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Two different soils were amended with 14C-labelled plant material and incubated under controlled laboratory conditions for 2 years. Half the samples were cropped with wheat (Triticum aestivum) 10 times in succession. At flowering, the wheat was harvested and the old roots removed from the soil, so that the soil was continuously occupied by predominantly active root systems. The remaining samples were maintained without plants under the same conditions. During the initial stages of high microbial activity, due to decomposition of the labile compounds, the size of the total microbial biomass was comparable for both treatments, and the metabolic quotient (qCO2-C = mg CO2-C·mg−1 Biomass C·h−1) was increased by the plants. During the subsequent low-activity decomposition stages, after the labile compounds had been progressively mineralized, the biomass was multiplied by a factor of 2–4 in the presence of plants compared to the bare soils. Nevertheless, qCO2-C tended to reach similar low values with both treatments. The 14C-labelled biomass was reduced by the presence of roots and qCO2-14C was increased. The significance of these results obtained from a model experiment is discussed in terms of (1) the variation in the substrate originating from the roots and controlled by the plant physiology, (2) nutrient availability for plants and microorganisms, (3) soil biotic capacities and (4) increased microbial turnover rates induced by the roots.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00260736
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  • 15
    Digitale Medien
    Digitale Medien
    Inoculation of field-grown wheat (Triticum aestivum) with Azospirillum spp. in Brazil (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 37-40 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Azospirillum brasilense ; Azospirillum amazonense ; rate reductase ; Inoculation ; Wheat ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Three field experiments with wheat were conducted in 1983, 1984, and 1985 in Terra Roxa soil in Paraná, the major Brazilian wheat-growing region, to study inoculation effects of various strains of Azospirillum brasilense and A. amazonense. In all three experiments inoculation with A. brasilense Sp 245 isolated from surface-sterilized wheat roots in Paraná produced the highest plant dry weights and highest N% in plant tops and grain. Grain yield increases with this strain were up to 31 % but were not significant. The application of 60 or 100 kg N ha−1 to the controls increased N accumulation and produced yields less than inoculation with this strain. Another A. brasilense strain from surface-sterilized wheat roots (Sp 107st) also produced increased N assimilation at the lower N fertilizer level but reduced dry weights at the high N level, while strain Sp 7 + Cd reduced dry weights and N% in the straw at both N levels. The A. amazonense strain isolated from washed roots and a nitrate reductase negative mutant of strain Sp 245 were ineffective. Strains Sp 245 and Sp 107st showed the best establishment within roots while strain Cd established only in the soil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280348
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  • 16
    Digitale Medien
    Digitale Medien
    Colonization of wheat seedling (Triticum aestivum) roots by Pseudomonas fluorescens and Bacillus subtilis (1987)
    Springer
    Biology and fertility of soils 4 (1987), S. 41-46 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Competition ; Migration ; Colonization potential ; Replica printing ; Triticum aestivum ; Pseudomonas fluorescens ; Bacillus subtilis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Colonization patterns of Pseudomonas fluorescens and Bacillus subtilis on roots of wheat seedlings growing on water agar were studied qualitatively by replica printing and quantitatively by the plate count method. The results indicated a stronger colonization potential for P. fluorescens (up to 107 cfu/cm root) than for B. subtilis (up to 105 cfu/cm root). Although the numbers of both species were lower when inoculated together, the observed colonization patterns on the roots were comparable to those found with single inoculations. For none of these bacteria was active migration along the root surface in any direction observed, indicating that distal positions are reached mainly by a passive displacement on the root tip and elongating cells. Ecological implications of the observed phenomena are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280349
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  • 17
    Digitale Medien
    Digitale Medien
    Effect of certain herbicides on growth and pathogenicity of take-all fungus on wheat (Triticum aestivum L.) (1987)
    Springer
    Biology and fertility of soils 5 (1987), S. 31-35 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Gaeumannomyces graminis ; VegVetative growth ; Pathogenicity ; Herbicides ; Diquat+paraquat ; Glyphosate ; Dicamba ; Trifluralin ; Chlorsulfuron ; Chlorthal dimethyl ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The effects of Spray Seed (diquat + paraquat), Roundup (glyphosate), Banvel-D (dicamba), Treflan (trifluralin), Glean (chlorsulfuron) and Dacthal (chlorthal dimethyl) at concentrations of 0–500 ppm product on the vegetative growth, vigour and pathogenicity of Gaeumannomyces graminis var. tritici (Ggt) on wheat were examined. All herbicides with the exception of dicamba and chlorsulfuron inhibited fungal growth on potato dextrose agar (PDA) at concentrations 10–500-fold of rates recommended for use in the field. The vegetative growth of the pathogen growing out of straw colonized on PDA supplemented with 100 ppm diquat + paraquat or glyphosate was reduced by 47.4% and 42.4%, respectively. When portions of these colonies were subcultured onto unamended PDA, their growth and the pathogenicity of straw pieces colonized by these subcultures were found to be unaltered. Straw colonized by Ggt on agar amended with concentrations of diquat + paraquat or at all concentrations of glyphosate produced less root disease in wheat seedlings in comparison to those colonized on unamended agar. It is proposed that the reduced pathogenicity of inocula prepared on agar amended with these two herbicides is due to poor colonization by the pathogen of straw on these media, and that a similar effect on saprophytic colonization in the field could lead to a reduction in the field inocula of the pathogen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00264343
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  • 18
    Digitale Medien
    Digitale Medien
    Influence of biopores on root growth, water uptake and grain yield of wheat (Triticum aestivum) based on predictions from a computer model (1988)
    Springer
    Biology and fertility of soils 6 (1988), S. 315-321 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Biopores ; Root growth ; Transpiration ; Simulations ; Mechanical impedance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The use of vertical biopores by wheat (Triticum aestivum) seminal roots for easy access to the subsoil and the consequences for plant water supply and yield has been investigated by computer simulation. Parameters included were: biopore density and diameter, depth of cultivation and strength of the subsoil — all under a wide range of seasonal weather conditions. The model predicts that biopores add significantly to root penetration at depth, even at a density of 0.1% v/v of small, vertical pores, while 1.5% to 2.0% v/v can ensure maximum root penetration. When the growing season is shorter a larger number of biopores is needed to ensure timely root penetration to depth. With shallow tillage, biopores occur closer to the soil surface, and their importance is increased. Deeper root penetration invariably gives greater water uptake and transpiration, but may have a negative effect on grain yield, especially under the driest climatic conditions. An increase in early water use may result in less soil water being available during the grain-filling period. The effect of biopores on plant transpiration varies from year to year, depending on the amount of rain and its distribution in time, and on the amount of soil water stored at time of sowing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00261020
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  • 19
    Digitale Medien
    Digitale Medien
    Interspecific variation in sustained swimming ability of late pelagic stage reef fish from two families (Pomacentridae and Chaetodontidae) (1998)
    Springer
    Coral reefs 17 (1998), S. 111-119 
    Details
    ISSN: 1432-0975
    Schlagwort(e): Key words Dispersal ; coral reefs ; fish ; swimming ; Larvae ; Juveniles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract  Characteristics of the pelagic stages of reef fishes have generally been investigated at the family level, which may mask important differences among species. Here the variation in sustained swimming ability of the late pelagic stages is examined among species, within two families (Pomacentridae and Chaetodontidae). The pomacentrids displayed a 7.5-fold difference in sustained swimming ability across 24 species, while the chaetodontids displayed a 2-fold difference across 10 species. The variation within the Pomacentridae was not related to pelagic larval duration, post-settlement habitat or taxonomy. There was, however, a significant correlation between sustained swimming ability and total length (TL) of individuals (r=0.435, P〈0.0001). Differences in the mean distance swum by pomacentrid species, however, was most strongly related to differences in mean wet weight (r=0.814, P〈0.0001). When the mean distance swum by species was scaled with respect to mean TL there was still a strong correlation with mean wet weight (r=0.644, P〈0.005). Among chaetodontid individuals TL and sustained swimming ability were not correlated (r=−0.004, P=0.978). Furthermore, sustained swimming ability was not significantly related to the trans-oceanic distribution of species in either family. The variation in sustained swimming ability, however, may contribute to explanations of the observed levels of gene flow within populations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003380050104
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  • 20
    Digitale Medien
    Digitale Medien
    Surf-riding and oscillations of a ship in quartering waves (1995)
    Springer
    Journal of marine science and technology 1 (1995), S. 24-36 
    Details
    ISSN: 1437-8213
    Schlagwort(e): surf-riding ; nonlinear ; wave ; ship motion ; stability ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract The behavior of a ship encountering large regular waves from astern at low frequency is the object of investigation, with a parallel study of surf-riding and periodic motion paterns. First, the theoretical analysis of surf-riding is extended from purely following to quartering seas. Steady-state continuation is used to identify all possible surf-riding states for one wavelength. Examination of stability indicates the existence of stable and unstable states and predicts a new type of oscillatory surf-riding. Global analysis is also applied to determine the areas of state space which lead to surf-riding for a given ship and wave conditions. In the case of overtaking waves, the large rudder-yaw-surge oscillations of the vessel are examined, showing the mechanism and conditions responsible for loss of controllability at certain vessel headings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01240010
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  • 21
    Digitale Medien
    Digitale Medien
    Fossil midge associations and the historical status of fish in acidified lakes (1990)
    Springer
    Journal of paleolimnology 3 (1990), S. 113-127 
    Details
    ISSN: 1573-0417
    Schlagwort(e): paleoecology ; Chaoboridae ; Chironomidae ; fish ; acidification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Chaoborid and chironomid (Diptera) fossils were examined in sediment cores form nine Ontario Precambrian Shield lakes that were fishless in 1979. An abundance of Chaoborus americamus (intolerant of predation by fish) throughout cores from four lakes indicated that they were fishless historically. Occurrence of Chaoborus punctipennis and C. flavicans and absence of C. americanus in cores, except near the surface in two cases, indicated that four other lakes were inhabited by fish historically. One of these was probably periodically fishless as suggested by fluctuations among these Chaoborus species. The ninth lake was not suitable for Chaoborus; only one specimen of C. trivittatus was found in this core. Chironomid fossil associations were substantially different in historically fishless and inhabited lakes. Fishless lakes had chironomids typical of eutrophic conditions indicating that seasonal oxygen depletion likely was inimical to fish. Chironomid associations of oligotrophic waters occurred in lakes historically inhabited by fish. Both good water quality and accessibility were required for long-term habitation by fish. Partial recovery of alkalinity and rise in pH were accompanied by substantial re-invasion by fish in two lakes which had been inhabited historically by fish. Diptera associations provide valuable information on the historical suitability of lakes for fish and the presence/absence of fish in regions where acidification of surface waters has occurred.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00414066
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  • 22
    Digitale Medien
    Digitale Medien
    Chaoborus (Diptera: Chaoboridae) mandibles—paleolimnological indicators of the historical status of fish populations in acid-sensitive lakes (1990)
    Springer
    Journal of paleolimnology 4 (1990), S. 139-151 
    Details
    ISSN: 1573-0417
    Schlagwort(e): Chaoborus ; Chaoboridae ; Diptera ; fish ; acidification ; paleolimnology ; Adirondacks ; Bosmina
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Paleolimnological analyses of Chaoborus mandibles were used to assess the status of fish populations over the previous 150 to 300 years in five lakes from the Adirondack region of New York State. Windfall Pond (pH 6.5) has not acidified and currently has viable fish populations. Big Moose Lake (pH 5.0) has acidified in recent years, and the number of fish populations declined from 14 in the 1930's to seven in the early 1980's. The occurrence of only migratory Chaoborus (subgenus Sayomyia) in the cores indicated the long term presence of fish populations in Windfall Pond and Big Moose Lake. Brooktrout Lake (pH 5.0), Deep Lake (pH 4.7) and Upper Wallface Pond (pH 4.8) have all acidified in recent years, and all three are currently fishless. Chaoborus (Sayomyia) was present throughout the Brooktrout Lake core, but the entirely limnetic species, C. americanus, appeared in the topmost interval in the core. The appearance of C. americanus in the top of the core indicated a recent elimination of fish from Brooktrout Lake, probably during the 1970's. Elimination of fish by the 1940's was inferred for Deep Lake because C. americanus appeared above the 1930 level and replaced C. trivittatus as the dominant. Dominance of C. americanus throughout the Upper Wallface Pond core indicated that planktivorous fish were never present. These results strongly suggest that stratigraphic analyses of Chaoborus mandibles provide a useful assessment of the general status of historical fish populations in Adirondack lakes. The technique should be useful in other regions, as well as for applications other than those concerning lake acidification.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00226321
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  • 23
    Digitale Medien
    Digitale Medien
    A note on multiple flow equilibria (1989)
    Springer
    Pure and applied geophysics 130 (1989), S. 743-749 
    Details
    ISSN: 1420-9136
    Schlagwort(e): Dynamic systems ; multiple equilibrium ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A set of ordinary differential equations describing a mechanical system subject to forcing and dissipation is considered. A topological argument is employed to show that if all time-dependent solutions of the governing equations are bounded, the equations admitN steady solutions, whereN is a positive odd integer and where at least (N−1)/2 of the steady solutions are unstable. The results are discussed in the context of atmospheric flows, and it is shown that truncated forms of the quasigeostrophic equations of dynamic meteorology and of Budyko-Sellers climate models satisfy the hypotheses of the theorem.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00881609
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  • 24
    Digitale Medien
    Digitale Medien
    Infectivity and acetylene reduction of diazotrophic rhizosphere bacteria in wheat (Triticum aestivum) seedlings under gnotobiotic conditions (1985)
    Springer
    Biology and fertility of soils 1 (1985), S. 123-129 
    Details
    ISSN: 1432-0789
    Schlagwort(e): Rhizosphere bacteria ; Nitrogenase activity ; Triticum aestivum ; Inoculation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Wheat seedlings were inoculated with rhizosphere nitrogen-fixing bacteria and grown gnotobiotically for 15 days. The growth medium consisted of semisolid agar with or without plant nutrients. The bacteria, isolated from roots of field-grown wheat, were three unidentified Gram-negative rods (A1, A2, E1), one Enterobacter agglomerans (C1) and two Bacillus polymyxa (B1, B2). A strain of Azospirillum brasilense (USA 10) was included for comparison. Nitrogenase activity (acetylene reduction activity, ARA) was tested on intact plants after 8 and 15 days of growth. In semisolid agar without plant nutrients, five isolates showed ARA of 0.01–0.9 nmol C2H4 plant−1 h−1, while the two strains of B. polymyxa had higher ARA of 3.3–10.6 nmol C2H4 plant−1 h−1. Plant development was not affected by inoculation with bacteria, except that inoculation with B. polymyxa resulted in shorter shoots and lower root weight. Transmission electronmicroscopy of roots revealed different degrees of infection. A. brasilense, A1 and A2, occurred mainly in the mucilage on the root surface and between outer epidermal cells (low infectivity). B. polymyxa strains and E1 were found in and between epidermal cells (intermediate infectivity) while E. agglomerans invaded the cortex and was occasionally found within the stele (high infectivity).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00301779
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  • 25
    Digitale Medien
    Digitale Medien
    Effects of 15N-labelled ammonium nitrate and urea on soil nitrogen during growth of wheat (Triticum aestivum L.) under field conditions (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 232-236 
    Details
    ISSN: 1432-0789
    Schlagwort(e): 15N-labelled fertilizer ; Added N interaction ; Fertilizer N uptake ; Soil N uptake ; Wheat ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We studied the effects of 15N-labelled ammonium nitrate and urea on the yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L., cv. Mexi-Pak-65) in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 33.6–51.5 and 30.5–40.9% of the N from ammonium nitrate and urea, respectively. Splitting the fertilizer N application had a significant effect on the uptake of fertilizer N by the wheat. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the two N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied according to the fertilizer N split; six split applications gave the highest added N interaction compared to a single application or two split applications for both fertilizers. Ammonium nitrate gave 90.5, 33.5, and 48.5% more added N interaction than urea with one, two, and six split N applications. A values were not significantly correlated with the added N interaction (r=0.557). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N replaced unlabelled soil N.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00336328
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  • 26
    Digitale Medien
    Digitale Medien
    Suppression of wheat early growth in standing stubble (2000)
    Springer
    Sciences of soils 5 (2000), S. 10-21 
    Details
    ISSN: 1432-9492
    Schlagwort(e): Soil temperature ; Triticum aestivum ; Stubble retention ; Nitrogen ; Early growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Early growth and development are often lower when wheat is sown into standing stubble. A study was conducted to determine whether this difference in early growth could be explained by the effects of stubble on soil temperature in the vicinity of the young plant. The roles of nitrogen nutrition and soil strength were also assessed. Three crops were monitored (1990–1992), with the wheat being sown into either standing wheat stubble after a no-till fallow (NT), or into no-tilled plots from which the stubble had been removed by burning (NB). Measurements were made of wheat growth and development, soil and plant N, soil temperature and penetration resistance. The site was on a black earth near Warialda in the northern wheatbelt of New South Wales, Australia. In 1992 wheat was also grown under simulated stubble to isolate the shading and soil temperature effects of stubble from other factors. A significant (P〈0.05) relationship was found between average soil temperature and above ground dry matter (DM) at 65 days after sowing (DAS) but not at 107 DAS. This relationship accounted for differences in DM production at 65 DAS between NT and NB treatments in 1991 and 1992, but not in 1990. In that year the lower DM production in NT plots was associated with poorer N nutrition, and possibly disease. Laboratory incubations indicate that immobilisation of N as stubble decomposed could have contributed to this. Burning stubble produced no immediate increase in soil N availability, so that it is unlikely that N contained in stubble contributed to the difference. Soil strength differences between treatments and phytotoxic effects are unlikely to have contributed to growth differences in this soil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s10112-000-0002-3
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  • 27
    Digitale Medien
    Digitale Medien
    Bifurcations in Spherical MHD Models (1998)
    Springer
    Studia geophysica et geodaetica 42 (1998), S. 320-327 
    Details
    ISSN: 1573-1626
    Schlagwort(e): MHD ; stability ; bifurcations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie , Physik
    Notizen: Abstract A series of numerical studies on the behaviour of magnetic fields and motions in a spherical body of an electrically conducting incompressible fluid have been carried out. The magnetic field was assumed to be maintained by a given electromotive force inside the body and to continue as a potential field in outer space. In view of the motion an external forcing was taken into account, and boundary conditions were considered which correspond to a stress-free surface. The stability of several steady states has been studied as well as the evolutions starting from unstable states. In this paper a configuration with a poloidal magnetic field and a differential rotation, both symmetric about the same axis, is considered. This configuration is stable only for sufficiently small Hartmann numbers but evolves, if disturbed, in the case of larger Hartmann numbers toward a non-axisymmetric state. In this case the well-known symmetrization effect of differential rotation in magnetic fields is destroyed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023356720631
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  • 28
    Digitale Medien
    Digitale Medien
    The Equation of State of Lakes (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 1-17 
    Details
    ISSN: 1573-1421
    Schlagwort(e): lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009626325650
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  • 29
    Digitale Medien
    Digitale Medien
    Accumulation of mercury in estuarine food chains (1998)
    Springer
    Biogeochemistry 40 (1998), S. 235-247 
    Details
    ISSN: 1573-515X
    Schlagwort(e): fish ; invertebrates ; ligands ; mercury ; methylmercury ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract To understand the accumulation of inorganic mercury and methylmercury at the base of the estuarine food chain, phytoplankton (Thalassiosira weissflogii) uptake and mercury speciation experiments were conducted. Complexation of methylmercury as methylmercury-bisulfide decreased the phytoplankton uptake rate while the uptake rate of the methylmercury-cysteine and -thiourea complexes increased with increasing complexation by these ligands. Furthermore, our results indicated that while different ligands influenced inorganic mercury/methylmercury uptake by phytoplankton cells, the ligand complex had no major influence on either where the mercury was sequestered within the phytoplankton cell nor the assimilation efficiency of the mercury by copepods. The assimilation efficiency of inorganic mercury/methylmercury by copepods and amphipods feeding on algal cells was compared and both organisms assimilated methylmercury much more efficiently; the relative assimilation efficiency of methylmercury to inorganic mercury was 2.0 for copepods and 2.8 for amphipods. The relative assimilation is somewhat concentration dependent as experiments showed that as exposure concentration increased, a greater percentage of methylmercury was found in the cytoplasm of phytoplankton cells, resulting in a higher concentration in the copepods feeding on these cells. Additionally, food quality influenced assimilation by invertebrates. During decay of a T. weissflogii culture, which served as food for the invertebrates, copepods were increasingly less able to assimilate the methylmercury from the food, while even at advanced stages of decay, amphipods were able to assimilate mercury from their food to a high degree. Finally, fish feeding on copepods assimilated methylmercury more efficiently than inorganic mercury owing to the larger fraction of methylmercury found in the soft tissues of the copepods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005959211768
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  • 30
    Digitale Medien
    Digitale Medien
    The use of polynomial regression analysis with indicator variables for interpretation of mercury in fish data (1998)
    Springer
    Biogeochemistry 40 (1998), S. 189-201 
    Details
    ISSN: 1573-515X
    Schlagwort(e): binary variables ; fish ; impoundment ; indicator variables ; James Bay ; mercury ; polynomial regression ; Québec ; reservoirs
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Mercury levels in fish in reservoirs and natural lakes have been monitored on a regular basis since 1978 at the La Grande hydroelectric complex located in the James Bay region of Québec, Canada. The main analytical tools historically used were analysis of covariance (ANCOVA), linear regression of the mercury-to-length relationship and Student-Newman-Keuls (SNK) multiple comparisons of mean mercury levels. Inadequacy of linear regression (mercury-to-length relationships are often curvilinear) and difficulties in comparing mean mercury levels when regressions differ lead us to use polynomial regression with indicator variables. For comparisons between years, polynomial regression models relate mercury levels to length (L), length squared (L2), binary (dummy) indicator variables (Bn), each representing a sampled year, and the products of each of these explanatory variables (L × B1, L2 × B1, L × B2, etc.). Optimal transformations of the mercury levels (for normality and homogeneity) were found by the Box-Cox procedure. The models so obtained formed a partially nested series corresponding to four situations: (a) all years are well represented by a single polynomial model; (b) the year-models are of the same shape, but the means may differ; (c) the means are the same, but the year-models differ in shape; (d) both the means and shapes may differ among years. Since year-specific models came from the general one, rigorous statistical comparisons are possible between models. Polynomial regression with indicator variables allows rigorous statistical comparisons of mercury-to-length relationships among years, even when the shape of the relationships differ. It is simple to obtain accurate estimates of mercury levels at standardized length, and multiple comparisons of these estimations are simple to perform. The method can also be applied to spatial analysis (comparison of sampling stations), or to the comparison of different biological forms of the same species (dwarf and normal lake whitefish).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005997430906
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  • 31
    Digitale Medien
    Digitale Medien
    Temperature, growth and dietary effects on fish mercury dynamics in two Ontario lakes (1998)
    Springer
    Biogeochemistry 40 (1998), S. 175-187 
    Details
    ISSN: 1573-515X
    Schlagwort(e): bioenergetics ; fish ; mercury ; methylmercury ; models
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract A bioenergetics-based model was used to investigate the effects of temperature, growth and dietary exposure on methylmercury dynamics in walleye (Stizostedion vitreum) and yellow perch (Perca flavescens) from two lakes sampled in northwestern Ontario. Orange Lake was smaller, warmer, had slower fish growth and higher mercury concentrations in yearling yellow perch and walleye (three fold difference in 40 cm walleye) than Trout Lake. The model was applied to test the hypothesis that higher water temperatures in Orange Lake increased metabolic needs, food consumption and mercury uptake in fish. The effects of different growths rates in the lakes were also considered. Temperature/metabolic effects and growth effects on internal methylmercury dynamics in walleye and perch were predicted to occur but be of secondary importance. Different dietary exposure to methylmercury was likely the dominant source of variation in fish mercury concentrations between the two lakes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005986505407
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  • 32
    Digitale Medien
    Digitale Medien
    Fish mercury levels in relation to characteristics of hydroelectric reservoirs in Newfoundland, Canada (1998)
    Springer
    Biogeochemistry 40 (1998), S. 217-233 
    Details
    ISSN: 1573-515X
    Schlagwort(e): Canada ; fish ; hydroelectric reservoirs ; mercury ; Newfoundland ; return time
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract Mercury levels in fish have been demonstrated to increase after impoundment with augmented levels of mercury predicted to decline as the reservoir ages. Previous research in Newfoundland predicted return rates in the order of 10 to 12 years for landlocked Atlantic salmon or ouananiche (Salmo salar) and 7 years for brook trout (Salvelinus fontinalis). In order to test the validity of these predictions on a broader spatial and temporal scale, and develop more generally predictive ‘models’, mercury levels in three fish species were studied in 16 older Newfoundland hydroelectric reservoirs of various age (32 to 95 years) and area flooded (21 to 13,000 ha). Mercury concentrations were standardized to fish length and correlated with physical, chemical, and biological characteristics of the sampling sites. Standard length mercury levels ranged from 0.23 to 0.86 ppm in ouananiche, 0.13 to 0.59 ppm in brook trout, and 0.22 to 0.72 in arctic charr (Salvelinus alpinus). Fish in excess of the Canadian Safety Limit (0.5 ppm) were collected from 14 of 16 sites for ouananiche, 8 of 17 sites for brook trout, and 3 of 7 sites for arctic charr, including control lakes. Standard length fish mercury levels were correlated with reservoir age and (log10) area flooded for ouananiche and with pH for arctic charr. A multiple regression model was developed relating standard length mercury in ouananiche with reservoir age and log10 of the flooded area. There were no apparent relationship between reservoir characteristics and brook trout mercury concentrations. Based on this analysis, it is not possible, at present, to develop generally predictive models for all species found in Newfoundland impoundments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005975714493
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  • 33
    Digitale Medien
    Digitale Medien
    Effect of rock discontinuities on certain rock strength and fracture energy parameters under uniaxial compression (1993)
    Springer
    Geotechnical and geological engineering 11 (1993), S. 81-105 
    Details
    ISSN: 1573-1529
    Schlagwort(e): Rock discontinuities ; uniaxial compression ; fracture mechanics ; stability ; scale effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Summary Five series of test blocks of Pendeli marble with artificially created discontinuities of different crack densities (simulating three mutually orthogonal joint sets) were tested in uniaxial compression in order to study the effect of discontinuities on: (a) the compressive strength and the modulus of elasticity, and (b) certain fracture energy parameters expressed by the ratio W A/W V, where W A is the surface energy and W V the volume elastic strain energy. Mathematical relationships are derived similar to those suggested by other authors relating strength parameters to crack densities. Such relationships clearly show a reduction in strength with increased crack density. The experimental results obtained permit the extension of Persson's relation (which refers to ideal intact rock) to the more realistic case of discontinuous rock mass by introducing the appropriate term that takes into consideration the effect of rock mass discontinuities on the energy ratio W A/W V. A comparison between laboratory results and field observations was subsequently carried out assuming the rock mass to behave as a linearly elastic material, obeying the Hoek and Brown failure criterion. This comparison showed that laboratory results can be extended to larger scale. Furthermore, in order to predict the in situ strength and stability of a rock mass in uniaxial compression (which is of major importance in underground excavations) certain concepts are proposed based on laboratory tests, in situ investigations and first principles of linear elastic fracture mechanics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00423337
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  • 34
    Digitale Medien
    Digitale Medien
    The effect of normal stress-friction angle relationship on the stability analysis of a rockfill dam (1994)
    Springer
    Geotechnical and geological engineering 12 (1994), S. 113-121 
    Details
    ISSN: 1573-1529
    Schlagwort(e): Greywacke ; normal stress ; rockfill ; shear strength ; stability ; triaxial testing
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Summary Accurate stability analysis must consider the variation of the angle of friction of rockfill with the confining pressure. In reality, with increasing depth of a rockfill dam, the apparent friction angle decreases, whereas near the surface it tends to be higher. Conventional methods which employ a constant friction angle throughout the depth of a rockfill shell often yield a lower factor of safety (conservative) for shallow slip planes. On the contrary, they produce a higher factor of safety for deepseated slips subjected to increased normal (confining) stresses. This paper compares the constant friction angle approach with the variable friction angle method based on the stability analysis of a large rockfill dam, and the associated practical implications are discussed. In the latter analysis, the effect of normal stress on the friction angle of rockfill is incorporated through experimental observations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00429769
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  • 35
    Digitale Medien
    Digitale Medien
    Improvements in resource recovery at Stauffer's Big Island Mine (1988)
    Springer
    Geotechnical and geological engineering 6 (1988), S. 195-214 
    Details
    ISSN: 1573-1529
    Schlagwort(e): Room and pillar mining ; yield pillars ; rock mechanics ; stability ; evaporites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Summary Significant increases in extraction ratio on the order of 6 to 8%, equivalent to as much as 142 t/m of panel advance, have occurred at the Big Island Mine during the last five years with the help of a practical rock mechanics program. This increase in resource recovery has also contributed to improvements in productivity. Both conventional and continuous machine mining have been used to mine two flat-laying trona beds at depths of 250 and 260 m in the Green River Formation in southwestern Wyoming. Conventional room and pillar mining originally was conducted in panels with extraction ratios of 58 to 60%. The use of yield pillars has allowed the panel extraction to increase to 66%. Continuous machine mining was introduced recently, with a 64% extraction ratio using long, narrow pillars and wide rooms. Further improvements in resource recovery seem feasible in the light of present mining experience. The rock mechanics program consisted of field instrumentation to determine the pillar and roof response to mining, and computer modelling to evaluate and help determine the stability of various layouts, which were then adopted for mining.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00880974
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  • 36
    Digitale Medien
    Digitale Medien
    Onset of viscous fingering for miscible liquid-liquid displacements in porous media (1993)
    Springer
    Transport in porous media 10 (1993), S. 285-291 
    Details
    ISSN: 1573-1634
    Schlagwort(e): Miscible displacement ; stability ; length effect ; critical velocity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract The displacement of one fluid by another miscible fluid in porous media is an important phenomenon that occurs in petroleum engineering, in groundwater movement, and in the chemical industry. This paper presents a recently developed stability criterion which applies to the most general miscible displacement. Under special conditions, different expressions for the onset of fingering given in the literature can be obtained from the universally applicable criterion. In particular, it is shown that the commonly used equation to predict the stable velocity ignores the effects of dispersion on viscous fingering.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00616814
    Standort Signatur Erwartet Verfügbarkeit
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  • 37
    Digitale Medien
    Digitale Medien
    Heat and mass transfer in unsaturated porous media at a hot boundary: I. One-dimensional analytical model (1991)
    Springer
    Transport in porous media 6 (1991), S. 281-298 
    Details
    ISSN: 1573-1634
    Schlagwort(e): Seasonal heat storage ; heat transport ; unsaturated soils ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract We present a model of heat and mass transfer in an unsaturated zone of sand and silty clay soils, taking into account the effects of temperature gradients on the advective flux, and of the enhancement of thermal conduction by the process of latent heat transfer through vapor flow. The motivation for this study is to supply information for the planned storage of thermal energy in unsaturated soils and for hot waste storage. Information is required on the possibility of significant drying at a hot boundary, as this would reduce the thermal conductivity of a layer adjacent to the boundary and, thus, prevent effective heat transfer to the soil. This study indicates the possibility that the considered system may be unstable, with respect to the drying conditions, with the occurrence of drying depending on the initial and the boundary conditions. An analysis performed for certain boundary conditions of heat transfer and for given soil properties, disregarding the advective flux of energy, indicated that there are initial conditions of water content for which heating will not cause significant drying. Under these conditions, fine soils may be better suited for heat transfer at the hot boundary, due to their higher field capacity, although their heat conduction coefficients at saturation are lower than those of sandy soils. At present, these conclusions are limited to the range of 50–80°C. Potential effects of solute concentration at the hot boundary are indicated.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00208954
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  • 38
    Digitale Medien
    Digitale Medien
    Orbital Migration Of Giant Planets: Using Numerical Integration To Investigate Consequences For Other Bodies (1999)
    Springer
    Earth, moon and planets 87 (1999), S. 103-115 
    Details
    ISSN: 1573-0794
    Schlagwort(e): Accretion ; exoplanetary system ; extrasolar planets ; numerical integration ; orbital migration ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A number of extrasolar planets have been detected in close orbits around nearby stars. It is probable that these planets did not form in these orbits but migrated from their formation locations beyond the ice line. Orbital migration mechanisms involving angular momentum transfer through tidal interactions between the planets and circumstellar gas-dust disks or by gravitational interaction with a residual planetesimal disk together with several means of halting inward migration have been identified. These offer plausible schemes to explain the orbits of observed extrasolar giant planets and giant planets within the Solar System. Recent advances in numerical integration methods and in the power of computer workstations have allowed these techniques to be applied to modelling directly the mechanisms and consequences of orbital migration in the Solar System. There is now potential for these techniques also to be applied to modelling the consequences of the orbital migration of planets in the observed exoplanetary systems. In particular the detailed investigation of the stability of terrestrial planets in the habitable zone of these systems and the formation of terrestrial planets after the dissipation of the gas disk is now possible. The stability of terrestrial planets in the habitable zone of selected exoplanetary systems has been established and the possibility of the accretion of terrestrial planets in these systems is being investigated by the author in collaboration with Barrie W. Jones (Open University), and with John Chambers (NASA-Ames) and Mark Bailey of Armagh Observatory, using numerical integration. The direct simulation of orbital migration by planetesimal scattering must probably await faster hardware and/or more efficient algorithms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017996927696
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