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  • 1
    Electronic Resource
    Electronic Resource
    Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves of Clusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela (1996)
    Springer
    Trees 10 (1996), S. 351-358 
    Details
    ISSN: 0931-1890
    Keywords: Key words Altitude ; Carbon isotope ratio ; Clusiaceae ; Crassulacean acid metabolism ; Deuterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Samples of the Clusiaceae genera Clusia, Oedematopus and Dystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i. e. carbon isotope discrimination (Δ), hydrogen isotope ratio (δD) and N-levels, and with altitude were assessed. In the samples, where values of Δ above 15 ‰ indicate predominant performance of C3 photosynthesis, there were slight tendencies of increasing Δ, δD and N-levels with increasing altitude and of increasing Δ with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species of Clusia appears to be restricted to altitudes below 1500 m a. s. l. There was a significant negative correlation of Δ with altitude in the samples, where values of Δ below 10 ‰ indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM in Clusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM in Clusia and trigger C3-CAM transitions in C3/CAM intermediate species, low availability of water is the most important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185638
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  • 2
    Electronic Resource
    Electronic Resource
    Estimates of nitrogen fixation by trees on an aridity gradient in Namibia (1991)
    Springer
    Oecologia 88 (1991), S. 451-455 
    Details
    ISSN: 1432-1939
    Keywords: Nitrogen fixation ; Carbon isotope ratio ; Nitrogen isotope ratio ; Acacia ; Namibia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Nitrogen (N2) fixation was estimated along an aridity gradient in Namibia from the natural abundance of 15N (δ15N value) in 11 woody species of the Mimosacease which were compared with the δ15N values in 11 woody non-Mimosaceae. Averaging all species and habitats the calculated contribution of N2 fixation (N f ) to leaf nitrogen (N) concentration of Mimosaceae averaged about 30%, with large variation between and within species. While in Acacia albida N f was only 2%, it was 49% in Acacia hereroensis and Dichrostachys cinerea, and reached 71% in Acacia melifera. In the majority of species N f was 10–30%. There was a marked variation in background δ15N values along the aridity gradient, with the highest δ15N values in the lowland savanna. The difference between δ15N values of Mimosaceae and non-Mimosaceae, which is assumed to result mainly from N2 fixation, was also largest in the lowland savanna. Variations in δ15N of Mimosaceae did not affect N concentrations, but higher δ15N-values of Mimosaeae are associated with lower carbon isotope ratios (δ13C value). N2 fixation was associated with reduced intrinsic water use efficiency. The opposite trends were found in non-Mimosaceae, in which N-concentration increased with δ15N, but δ13C was unaffected. The large variation among species and sites is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317592
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Relationships between carbon and hydrogen isotope ratios and nitrogen levels in leaves ofClusia species and two other Clusiaceae genera at various sites and different altitudes in Venezuela (1996)
    Springer
    Trees 10 (1996), S. 351-358 
    Details
    ISSN: 1432-2285
    Keywords: Altitude ; Carbon isotope ratio ; Clusiaceae ; Crassulacean acid metabolism ; Deuterium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Samples of the Clusiaceae generaClusia, Oedematopus andDystovomita were collected at various sites and different altitudes in northern and south-western Venezuela. Analyses of stable isotopes of carbon and hydrogen and of leaf-nitrogen levels were performed on the dried samples. Correlations among these variables, i.e. carbon isotope discrimination (Δ), hydrogen isotope ratio (δD) and N-levels, and with altitude were assessed. In the samples, where values of Δ above 15‰ indicate predominant performance of C3 photosynthesis, there were slight tendencies of increasing Δ, δD and N-levels with increasing altitude and of increasing Δ with increasing N. Although these correlations taken separately were not statistically significant, they support each other and indicate increasing transpiration and increased leaf-nutrient supply at increasing altitude. Performance of crassulacean acid metabolism (CAM) in species ofClusia appears to be restricted to altitudes below 1500 m a.s.l. There was a significant negative correlation of Δ with altitude in the samples, where values of Δ below 10‰ indicated predominant performance of CAM. This suggests that phases II and IV of CAM are progressively suppressed towards the upper altitudinal limit of CAM inClusia in northern Venezuela. It is concluded that among the large number of environmental factors and combinations thereof, which determine the expression of CAM inClusia and trigger C3-CAM transitions in C3/CAM intermediate species, low availability of water is the most important.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02185638
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
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