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  • 1
    ISSN: 1573-5036
    Keywords: air pollution ; ammonium sulphate ; Antennaria dioica ; Arnica montana ; Glomus fasciculatum ; heathland vegetation ; Hieracium pilosella
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three heathand species, Antennaria dioica, Arnica montana and Hieracium pilosella, were artificially rained with ammonium sulphate solutions at increasing concentrations in a greenhouse experiment. The same species were also artificially rained with increasing ammonium sulphate solutions under field conditions. Dry weights of the plants in the field experiments did not change with increasing ammonium sulphate applications. Nor did the dry weights of plants in the greenhouse experiments change with increasing ammonium sulphate concentrations, except for Arnica montana, which showed an increase in dry weight. VAM infection percentage of Antennaria dioica increased in both the greenhouse and the field experiment. The results of the field experiment show that VAM infection rates are reduced after two years of artificial rain in the plant species Arnica montana, which grows naturally under nutrient poor conditions and is presently declining in its natural habitat in the Netherlands. In the greenhouse experiment, VAM infection of Arnica montana did not change with increasing ammonium sulphate concentrations. VAM infection rates of Hieracium pilosella, which presently is not declining, did not change with increasing ammonium sulphate concentrations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 104 (1998), S. 181-203 
    ISSN: 1573-2932
    Keywords: coniferous ecosystems ; Douglas fir ; 15N ; NICCCE ; NITREX ; nitrogen ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract For a Douglas fir forest ecosystem subjected to an experimental decrease in nitrogen (N) deposition, N dynamics were simulated using the dynamic simulation model NICCCE. Meteorological driving variables and N concentrations in throughfall were input to the model, that simulated results of a 15N tracer experiment, C and N concentrations in the soil, soil water chemistry and tree biomass. Four years of ambient N deposition, followed by four years of N deposition manipulations by means of a roof construction beneath the forest canopy, were modelled. Simulation of this second period was performed for a high-N treatment (37 kg N ha-1 yr-1) and a low-N treatment with throughfall-N at natural background level (6 kg N ha-1 yr-1). Calibration and model performance is discussed and compared to results of field experiments. The quick response of soil water chemistry after lowering N deposition and the 15N tracer signal observed in soil water at 90 cm soil depth, were simulated closely by the calibrated model. 15NH4-N data could only be simulated by accounting for bypass flow, indicating that throughfall water did not fully interact with the soil. Using the calibrated parameter set of the low-N treatment for the high-N treatment resulted in a lower model performance, although time trends were reproduced well also for this treatment. A sensitivity analysis showed model outcome of N transformations to be very sensitive to soil microbial parameters, such as the C efficiency. Use of the 15N tracer data in the calibration lowered uncertainties of these sensitive model parameters. Evaluation of the N input-output budget and microbial N transformations in the ecosystem revealed that lowering N inputs in this N saturated forest soil resulted in a more than proportional decrease of N leaching losses out of the soil system. Gross N transformations decreased under lowered N input, in particular the formation of NO3-N. Net N mineralization was not affected after four years of N manipulations. Net nitrification was decreased to about one third of the rate observed at the high-N deposition plot. Combining 15N tracer data with dynamic simulation modelling provides a powerful tool to improve model performance and process descriptions, and to evaluate impacts of atmospheric N deposition on N cycling in ecosystems.
    Type of Medium: Electronic Resource
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