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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 180 (1996), S. 219-230 
    ISSN: 1573-5036
    Keywords: Calamagrostis epigejos ; calcium ; decalcification ; pedogenesis ; revegetation ; Schoenus nigricans ; sod-cutting ; wet dune slack
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The development of vegetation and soil was investigated in wet coastal dune slacks in North Holland, The Netherlands (52°36'N, 4°37'E). Sod cutting in the past has created a time series from 1 to 30 years, with an even older undisturbed site as reference. After sod-cutting Schoenus nigricans, a typical pioneer species of wet dune slacks, established and contributed together with Calamagrostis epigejos to more than 85% of the aboveground biomass. At the control site the biomass was 9.5 t dry matter ha-1. the humus layer increased to a thickness of 11 cm. The concentration of nitrogen, phosphorus and potassium increased in the humus layer without strong effects on the sandy subsoil, in contrast to the strong decalcification in the subsoil. The velocity of the latter process was a factor of hundred higher than reported from dry dunes in the same area. Changes in nutrient amount and availability affected the element concentration in the two dominant plant species. The nitrogen concentration in shoots of S. nigricans was nearly constant over time, whereas that in shoots of C. epigejos declined by 80%. Due to the increasing biomass the size of the N- and P-pool of the biomass increased with the age of the plots. Processes of vegetation development and pedogenesis are not (yet) affected by decalcification as established by the nut mass of S. nigricans. It is concluded that decalcification is not the key factor for the disappearance of rare species. Due to the dominance and the height structure of the two dominant plant species competition for radiation and lack of bare soil for germination are discussed as main reason for losses in biodiversity. It is advised that mowing may be an effective management tool for hampering the soil formation; but sod-cutting may be necessary once in every decade.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 98 (1995), S. 413-416 
    ISSN: 1434-6036
    Keywords: 36.40.td ; 33.20.Kf ; 67.90.tZ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Large helium clusters, ranging in size from a few hundred to several thousand atoms, are produced in a nozzle expansion. Combining this source with a pick-up scattering cell in which the clusters can be seeded with chromophores allows us to probe the influence of the helium environment on the atoms and molecules attached to the clusters. Using an alkali as chromophore we recorded laser induced fluorescence spectra of Na atoms and molecules attached to helium clusters. Apart from the spectrum of the Na monomer, we have found spectroscopic bands which can unambiguous be assigned to two bound Na atoms. The first of this bands is due to 11 ∑ μ + (A) ← 11 ∑ g + (X) excitations of the covalently bound singlet Na2 molecule while the second is due to 13 ∑ g + ← 13 ∑ μ + excitations for the van der Waals bound triplet Na2 dimer. Both bands have been vibrationally resolved. Furthermore we found very large fluorescence intensities in the region 605–635 nm which are likely due to the excitation of a species containing three Na atoms attached to a helium cluster.
    Type of Medium: Electronic Resource
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