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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 67 (1982), S. 35-43 
    ISSN: 1573-5036
    Keywords: Agro-ecosystems ; Mathematical models ; N-cycling ; Simulation modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Los modelos de simulación del comportamiento en agro-ecosistemas difieren en dos características: (i)entereza o minuciosidad conceptual, en términos del número de procesos que considera, y (ii)el nivel de detalle en el cual cada proceso es modelado. Estas características del modelo son determinadas por los objetivos para los cuales el modelo es diseñado y por el grado acutal del conocimiento de los procesos incluídos en el modelo. Los niveles de entereza conceptual y de detalle en un modelo determinan las aplicaciones potenciales para las cuales dicho modelo puede ser utilizado. Las aplicationes pueden ser orientadas a la investigación, manejo o planificación. Un modelo adecuado para una aplicación determinada debería tener un nivel apropiado de entereza y detalle para lograr el objetivo establecido. Los criterios de ayuda en la selección y evaluación de los modelos de simulación del nitrógeno para una aplicación particular incluyen: (i) la disponibilidad de facilidades computacionales, (ii) las escalas espacial y temporal de aplicación, (iii) el uso deseado de las simulaciones, (iv) la disponibilidad de datos de entrada al modelo, y (v) los ámbitos de confianza asociadas con las salidas del modelo.
    Notes: Abstract Available simulation models for describing nitrogen behavior in agro-ecosystems vary in two characteristics:(i) conceptual completeness in terms of the number of processes considered, and(ii) thelevel of detail at which each process is modeled. These model characteristics are determined by both the objectives that the model is designed to meet and the current state-of-the-art understanding of the various processes included in the model. The levels of conceptual completeness and detail in a model govern the potential applications for which the model may be used. Applications of models may be research-oriented, management-oriented, or planning-oriented. A model suitable for a given application should have an appropriate level of completeness and detail to accomplish the stated objective. Criteria to aid in the selection and evaluation of nitrogen simulation models for a particular application include: i) the availability of computational facilities, ii) the spatial and temporal scales of application, iii) the intended use of the simulations, iv) the availability of model input data, and v) the confidence regions associated with the model output.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 159 (1988), S. 177-188 
    ISSN: 1573-5117
    Keywords: eutrophic lake water ; nitrogen flux ; anaerobic sediment ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen flux from sediment of a shallow lake and subsequent utilization by water hyacinth (Eichhornia crassipes [Mart] Solms) present in the water column were evaluated using an outdoor microcosm sediment-water column. Sediment N was enriched with 15N to quantitatively determine the movement of NH4-N from the sediment to the overlying water column. During the first 30 days. 48% of the total N uptake by water hyacinth was derived from sediment 15NH4-N. This had decreased to 14% after 183 days. Mass balance of N indicates that about 25% sediment NH4-N was released into the overlying water, but only 17% was assimilated by water hyacinth. NH4-N levels in the water column were very low, with very little or no concentration gradients. NH4-N levels in the interstitial water of the sediment were in the range of 30–35 mg L−1 for the lower depths (〉 35 cm), while in the surface 5 cm of depth NH4-N levels decreased to 3.2 mg L−1. Simulated results also showed similar trends for the interstitial NH4-N concentration of the sediment. The overall estimated NH4-N flux from the sediment to the overlying water was 4.8 µg cm−2 day−1, and the soluble organic N flux was 5.8 µg N cm−2 day−1. Total N flux was 10.6 µg N cm−2 day−1.
    Type of Medium: Electronic Resource
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