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  • Nitrogen  (2)
  • 12.20.Fv  (1)
  • Springer  (3)
  • Nature Publishing Group
  • American Meteorological Society (AMS)
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Years
  • 1
    Electronic Resource
    Electronic Resource
    Seasonal allocation of dry mass and nitrogen in a fynbos endemic Restionaceae species Thamnochortus punctatus Pill. (1987)
    Springer
    Oecologia 72 (1987), S. 315-320 
    Details
    ISSN: 1432-1939
    Keywords: Allocation patterns ; Restionaceae ; Nitrogen ; Dry mass ; Fynbos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The annual growth pattern of male plants of the endemic, dioecious fynbos species, Thamnochortus punctatus, revealed sequential growth of the various below-and above-ground organs. Root and rhizome development were favoured in the wet winter months while culm elongation occurred in the warmer but drier spring to summer period. The reproductive phase of development followed in the hot dry summer and autumn. The asynchronous pattern of growth is suggested to enable the plant to maximize utilization of scarce resources within the confines of the environmental controls determined by the mediterranean-climate. Maximum root and rhizome activity in the rainy season enabled the plant to absorb and store nitrogen in mature culms for later above ground organ development. As the absorption of nitrogen from senscing material is essential for this pattern of organ development to assist in alleviating nutrient scarcity the high degree of nitrogen reabsorption, 35 to 70% for branches and culms respectively, shows the potential importance of asynchronous organ growth in overcoming nitrogen limitation of plant growth. Comparisons of dry mass and nitrogen allocation patterns indicate that developmental strategies employed by evergreen, perennial plants in climatically and edaphically constrained environments cannot be deduced from biomass allocation patterns alone as they do not appear to reflect strategies evolved to overcome nutrient limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379284
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  • 2
    Electronic Resource
    Electronic Resource
    Bhabha to Møller cross section ratios in the energy range 2.15–2.45 MeV (1993)
    Springer
    The European physical journal 345 (1993), S. 79-88 
    Details
    ISSN: 1434-601X
    Keywords: 12.20.Fv ; 13.10.+q ; 14.80.Pb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The cross sections for Bhabha and Møller scattering have been investigated in the energy range 2.1–2.4 MeV using monoenergetic positrons and electrons to search for hypothetical resonances superimposed to the continuum predicted by quantum electro dynamics. Bhabba-to-Mott, Møller-to-Mott and Møller-to-Bhabha cross section ratios were measured. The Bhabha-to-Mott ratios could be determined with statistical errors of typically 1% and remaining systematic errors not exceeding the statistical ones. No resonances in Bhabha scattering were observed. Limits for the intrinsic widths of hypothetical resonances are given. For the first time upper limits are deduced from our data for hypothetical resonances in the Møller scattering cross section in the MeV range. Additionally, Møller-to-Bhabha cross section ratios could be determined with good precision. A good agreement between the experimental and theoretical Møller-to-Bhabha ratios can be stated calling in question the recently predicted existence of series of narrow, unresolvable resonances in the Bhabha scattering cross section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01290343
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  • 3
    Electronic Resource
    Electronic Resource
    Soil nutrient dynamics and community boundaries in the Fynbos vegetation of South Africa (1997)
    Springer
    Plant ecology 130 (1997), S. 143-153 
    Details
    ISSN: 1573-5052
    Keywords: Community boundaries ; Fynbos ; Nitrogen ; Phosphorus ; Soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between changes in soil nutrient characteristics and fynbos community boundaries was investigated near Cape Agulhas, South Africa. Soil characteristics relating to total nutrient content (pH, total N and total P, organic carbon, and various cations) were assessed at sites along three transects crossing the boundaries between five plant communities. Dynamics of available N and P in soils of three communities were studied in the field over one year, using ion-exchange resins. There was a wide range in the degree of change in soil nutrient content across different community boundaries. The characteristics that varied most were pH, total N, Ca and total P. Differences in available nutrients among soils indicated that the communities in this landscape were associated with a mosaic of N and P availability. It is proposed that spatial variation in soil nutrient availability rather than total soil nutrient contents may be important in explaining landscape-level species distributions and community composition in nutrient-poor mediterranean-climate ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009742225383
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