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  • Environment  (3)
  • model  (3)
  • 1
    ISSN: 1573-5036
    Keywords: architecture ; model ; root map ; root profile ; root system ; soil bulk density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Differences between observed and simulated vertical root maps were studied in an attempt to evaluate the predictive ability of a simulation model of root system architecture under field conditions on mature plants, and to identify avenues for improvement. Some methodological problems associated with root mapping in the field are considered with a sensitivity analysis. Comparisons were made on a maize crop (early maturing hybrid F1 cultivar ‘Dea’) 15 days after silking. Four vertical root maps, perpendicular to the row and midway between two successive plants, were observed. Simulated root maps for different locations along the row showed essentially the same pattern, attesting of an approximately two-dimensional distribution of the roots in such a crop. Simulation of the intesection of roots with thin layers (thickness from 0 to 20 mm) instead of a perfect plane allowed us to assess effects due to the roughness of actual trench walls, and possible artefacts in the observation of root intersections. The simulated root profiles were very sensitive to this thickness, especially in the 0–5 mm range, in both average values, and overall shape. Actual data were close to the 3 mm thick simulations. This value seems plausible under our field conditions. Differences between simulated and actual root maps were shown to be mostly accounted for by the variations in soil bulk density. Thus, this environmental parameter appears as the most important one to include into the model for improving its predictions.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 189 (1997), S. 81-89 
    ISSN: 1573-5036
    Keywords: methodology ; minirhizotron ; model ; root system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to help design experiments with minirhizotrons or interpret data from such experiments, a modelling approach is a valuable tool to complement empirical approaches. The general principle of this modelling approach is to calculate and to study the part of a theoretical root system that is intersected by passes through a virtual minirhizotron tube (modelled here as a cylinder). Various outputs can be calculated from this part of the root system, and related to the surrounding root system which is perfectly known, since it has been simulated and stored in a data structure. Therefore, the method involves two levels of modelling that are presented and discussed: the root system architecture of a crop, and the observations that can be achieved with minirhizotron tubes. Illustrations of the method are presented to study the effect of several factors on the rooting depth curves, and to show how images may be calculated to mimic what can actually be viewed from inside the tube. These first results show that the maximum rooting depth curves, as virtually observed in the minirhizotron tube, present large variations and strongly underestimate the maximum rooting depth of the modelled root system (up to 60 cm in average). The underestimation is still more critical when the radius of the tube is lower than 3 cm, and when the tube is close to the vertical (angle lower than 0.2 rad). The use of the 0.9 quantile instead of the average value, for each of the observation dates, leads to a better estimation of the maximum rooting depth.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: maize ; model ; root architecture ; root intersection ; root length ; stochastic geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The spatial distribution of root length density (RLD) is important because it affects water and nutrient uptake. It is difficult to obtain reliable estimates of RLD because root systems are very variable and heterogeneous. We identified systematic trends, clustering, and anisotropy as geometrical properties of root systems, and studied their consequences for the sampling and observation of roots. We determined the degree of clustering by comparing the coefficient of variation of a simulated root system with that of a Boolean model. We also present an alternative theoretical derivation of the relation between RLD and root intersection density (RID) based on the theory of random processes of fibres. We show how systematic trends, clustering and anisotropy affect the theoretical relation between RLD and RID, and the consequences this has for measurement of RID in the field. We simulated the root systems of one hundred maize crops grown for a thermal time of 600 K d, and analysed the distribution of RLD and root intersection density RID on regular grids of locations throughout the simulated root systems. Systematic trends were most important in the surface layers, decreasing with depth. Clustering and anisotropy both increased with depth. Roots at depth had a bimodal distribution of root orientation, causing changes in the ratio of RLD/RID. The close proximity of the emerging lateral roots and the parent axis caused clustering which increased the coefficient of variation.
    Type of Medium: Electronic Resource
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  • 4
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    In:  http://aquaticcommons.org/id/eprint/8536 | 424 | 2012-03-17 07:59:49 | 8536 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-07-03
    Description: Details are presented of a bacteriological study in Ebrié Lagoon (Abidjan-Côte d'Ivoire) conducted during Oct-Dec 1974. Sampling sites are shown, and estimated and confirmed values for coliforms are given. The significance of the values obtained is briefly discussed, but further important factors, such as meteorological conditions and state of the sea, need clarification before definite conclusions can be made.
    Keywords: Biology ; Ecology ; Environment ; Pollution ; Côte d'Ivoire ; Lagune Ebrié ; lagoons ; bacteria ; microbial contamination
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 97-101
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  • 5
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    In:  http://aquaticcommons.org/id/eprint/7950 | 424 | 2012-03-07 15:32:53 | 7950 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-06-26
    Description: The total coliforms, fecal coliforms and fecal streptococci were counted over 1 year at 33 stations in the Ebrié Lagoon near Abidjan (Ivory Coast). Most of the waters show high numbers of bacteria, (D category of the American standards). For the sea-beaches, high numbers of fecal germs are found where the human population is abundant.
    Keywords: Environment ; Health ; Pollution ; Côte d'Ivoire ; Lagune Ebrié ; Abidjan ; bacteria ; coloforms ; germs ; streptococci
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 43-50
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  • 6
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    In:  http://aquaticcommons.org/id/eprint/7491 | 424 | 2012-01-01 08:38:01 | 7491 | Centre de Recherches Océanographiques, Côte d'Ivoire
    Publication Date: 2021-07-03
    Description: Total CO2 of brackish water (Ebrié lagoon) is measured with a simple method: degassing and trapping CO2 in NaOh solution, the conductivity of which is a function of the trapped CO2 quantity. A relation CO2 versus salinity is deduced; it is nearly the same as the one deduced from CO2 measurements performed from alkalinity. Dissolved organic C is evaluated with a CHN analyser by evaporating 0.5 ml of acidified sample. Variation coefficient is near 10% for the lagoon values.
    Keywords: Ecology ; Environment ; Côte d'Ivoire ; organic carbon ; brackish water ; data analysis
    Repository Name: AquaDocs
    Type: article
    Format: application/pdf
    Format: application/pdf
    Format: 27-36
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