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  • Geophysics  (1)
  • Miombo typesavanna ecosystem  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Preliminary results on nitric oxide emission from a southern African savanna ecosystem (1997)
    Springer
    Nutrient cycling in agroecosystems 48 (1997), S. 123-138 
    Details
    ISSN: 1573-0867
    Keywords: Africa ; biogenic emission ; dry season ; dynamic chamber ; forest ; grassland ; groundnut ; maize ; Miombo typesavanna ecosystem ; nitric oxide ; pulsing ; sorghum ; wet season ; Zimbabwe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During October to December 1994, we measured diel and seasonal variability in nitric oxide (NO) exchange by a southern African savanna ecosystem (Grasslands Research Station, Marondera, Zimbabwe). A set of automated dynamic chambers was installed in three sub-sites: Miombo forest, natural grassland, and cropped soils (maize, sorghum, groundnut). The latter received a single application of commercialy available in-organic or cowdung fertilizer. The dynamic chamber system is described in detail, including correction of the resulting data for wall losses and gas-phase reactions of the NO-NO2-O3 triad. During the dry season, net vertical NO fluxes were close to the detection limit (0.44 ngN m-2s-1) regardless of vegetation type. During the transition from dry to wet season strong "pulsing" effects of the NO flux were observed: NO emissions increased by a factor of up to 60 within hours. During the wet season, NO emissions varied between the different sub-sites of the ecosystem; corresponding means are in ranking order of fertilized agricultural plots (27.2 ngN m-2 s-1), unfertilized agricultural plots (8.5 ngN m-2 s-1 ), grassland (4.4 ngN m-2 s-1 ), and Miombo forest (1.5 ngN m-2 s-1). Soil moisture was found to be the dominant factor controlling the NO fluxes. Whenever it was not limiting, the diel behaviour of NO emission followed the daily variation of soil temperature measured 1 cm below the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009765510538
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Interrelationships Between Aerosol Characteristics and Light Scattering During Late-winter in a Eastern Mediterranean Arid Environment (1999)
    In:  CASI
    Details
    Publication Date: 2013-04-10
    Description: An intensive field campaign involving measurement of various aerosol physical, chemical, and radiative properties was conducted at Sde Boker in the Negev Desert of Israel, from 18 February to 15 March 1997. Nephelometer measurements gave average background scattering coefficient values of about 25 M/m at 550 nm wavelength, but strong dust events caused the value of this parameter to rise up to about 800 M/m Backscattering fractions did not depend on aerosol loading, and generally fell in the range of 0.1 to 0.25, comparable to values reported for marine and Arctic environments. Chemical analysis of the aerosol revealed that, in the coarse size range (2 - 10 micrometer equivalent aerodynamic diameter (EAD)), calcium (Ca) was by far the most abundant element followed by silicon (Si), both of which are indicators for mineral dust. In the fine size fraction (〈 2 micrometers EAD), sulfur (S) generally was the dominant element, except during high dust episodes when Ca and Si were again the most abundant. Furthermore, fine black carbon (BC) correlates with S, suggesting that they may have originated from the same sources or source regions. An indication of the short-term effect of aerosol loading on radiative forcing was provided by measurements of global and diffuse solar radiation, which showed that during high turbidity periods (strong dust events) almost all of the solar radiation reaching the area is scattered or absorbed.
    Keywords: Geophysics
    Format: application/pdf
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