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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 80 (1989), S. 356-367 
    ISSN: 1432-1939
    Keywords: Carbon gain ; Exotic shrubs ; Leaf longevity ; Photosynthesis ; Understory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We compared seasonal trends in photosynthesis of two naturalized exotic shrubs (Rhamnus cathartica and Lonicera X bella) and two native shrubs (Cornus racemosa and Prunus serotina) in open and understory habitats in southern Wisconsin. We examined the relationships between resource availability and leaf photosynthetic performance in these four species. All four species had similar relationships between leaf nitrogen (N) content and photosynthetic rate, but the species differed in absolute leaf N content and therefore in photosynthetic rates. Maximum daily photosynthetic rates of all species were significantly correlated with leaf N content in the open habitat, but not in the understory, where low light availability was the major limitation to photosynthesis. Extended leaf longevity was important in the forest understory because it allowed shrubs to take advantage of high light availability at times when the overstory canopy was leafless. Early leaf emergence was more important than late senescence: from 27% to 35% of the annual carbon gain of P. serotina, R. cathartica, and L. X bella occurred prior to leaf emergence of C. racemosa, the species with the shortest leaf life span. Extended leaf longevity of exotic shrubs may help explain their persistence in the understory habitat, but it contributed relatively less to their annual carbon gain in the open habitat.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1939
    Keywords: Aboveground growth ; Carbon gain ; Exotic shrubs ; Leaf area ; Shrub productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In this study we compared the aboveground growth rates of two exotic shrubs (Rhamnus cathartica and Lonicera X bella) and two native shrubs (Cornus racemosa and Prunus serotina) that are important in southern Wisconsin hardwood forests. For all species except P. serotina, aboveground growth rates in an open habitat were greater than in an understory environment. Growth rates differed among species in the open habitat and were significantly correlated with woody production per unit leaf area. All species had greater leaf area per unit wood biomass in the understory than in the open habitat. A comparison of above-ground growth and annual carbon gain suggests much greater respiratory costs in the open habitat, especially for P. serotina. The data from this study were used to examine mechanisms of species response to different light availabilities. We found that the species that increased their production per unit leaf area in response to increased light did not increase their leaf area per unit wood biomass in response to low light, and vice versa. Production of proportionately high leaf area may be important for the growth of C. racemosa in low light.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Environmental management 11 (1987), S. 713-719 
    ISSN: 1432-1009
    Keywords: Global sustainability ; Ecologically sustainable development ; Sustainable use of the biosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Sustainability is increasingly viewed as a desired goal of development and environmental management. This term has been used in numerous disciplines and in a variety of contexts, ranging from the concept of maximum sustainable yield in forestry and fisheries management to the vision of a sustainable society with a steady-state economy. The meaning of the term is strongly dependent on the context in which it is applied and on whether its use is based on a social, economic, or ecological perspective, Sustainability may be defined broadly or narrowly, but a useful definition must specify explicitly the context as well as the temporal and spatial scales being considered. Although societies differ in their conceptualizations of sustainability, indefinite human survival on a global scale requires certain basic support systems, which can be maintained only with a healthy environment and a stable human population. A clearer understanding of global sustainability and the development of appropriate indicators of the status of basic support systems would provide a useful framework for policy making.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Environmental management 12 (1988), S. 133-143 
    ISSN: 1432-1009
    Keywords: Global sustainability ; Indicators ; Measurement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The widespread interest in the concept of sustainable environment and development has been accompanied by the need to develop useful systems of measurement. We discuss the use of indicators which might be used to assess such conditions. Our characteristics, or criteria, for desirable global sustainability indicators are: sensitivity to change in time sensitivity to change across space or within groups predictive ability availability of reference or threshold values ability to measure reversibility or controllability appropriate data transformation integrative ability relative ease of collection and use We discuss the basis of these characteristics, and examine two categories of indicators (soil erosion and population) and two specific indicators (physical quality of life index and energy imports as a percentage of consumption) for their value as sustainability measures.
    Type of Medium: Electronic Resource
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