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  • Carbon gain  (2)
  • Diversity  (2)
  • Structure  (2)
  • 1
    ISSN: 1573-5052
    Keywords: Canopy ; Carbon gain ; Flowering ; Herbs ; Leaf area index ; Light profile ; Nitrogen profile ; Photosynthesis ; Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using a combination of mathematical modeling and field studies we showed that in dense stands of growing herbaceous plants the vertical pattern of leaf nitrogen distribution resembles the pattern of mean light attenuation in the stand and hence tends to maximize total daily photosynthetic carbon gain of the whole stand. Flowering represents a strong sink of nitrogen away from the photosynthetic apparatus and in herbs like Solidago altissima it induces leaf shedding. We studied both the effect of nitrogen reallocation and leaf shedding on the whole canopy photosynthesis and changes in leaf nitrogen distributions in stands moving from the growing to the flowering stage. Despite a decrease in leaf area index and total nitrogen available for photosynthesis in the flowering stand, the leaf nitrogen distribution here also leads to an almost maximum canopy photosynthesis. In both the growing and the flowering stands the leaf area index was higher than calculated optimum values. It is pointed out that this should not necessarily be interpreted as ‘non-adaptive’.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 102 (1992), S. 183-199 
    ISSN: 1573-5052
    Keywords: Diversity ; Canary Islands ; Endemism ; Fruits ; Island flora ; Mediterranean ; Succulence ; Spinescence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An analysis is given of the growth form composition of the flora of the Canary Islands based on a checklist published by Hansen & Sunding (1985) and the authors' field studies. Results are compared with similar data available from Israel and California. Special attention is given to endemism, the Mediterranean-wides and introduced species, as well as to some special plant features such as succulence, spinescence and fleshy fruits. Long-distance dispersal is stressed as the mechanism by which the Canaries obtained their flora. The growth-form composition of the Canaries is discussed in the context of the prevailing present-day environmental conditions, not in the context of climatic conditions in geological time. Characteristic features are the low percentages of endemic and even of indigenous annuals, the high percentage of chamaephytes (many of whom are endemic), the strong development of arborescence, the richness in leaf succulents, and the paucity of spines.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5052
    Keywords: Africa ; Diversity ; Dominance ; Grassland ; Miombo woodland ; Plant strategies ; Principal Components Analysis ; Reciprocal Averaging ; Rhodesia ; Serpentine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Contrasts in physiognomy and floristic composition of the vegetation of serpentine and non-serpentine substrates are very strong in the northern part of the Rhodesian Great Dyke, and the boundaries between these types are very sharp. Principal components analysis and reciprocal averaging are used to carry out a gradient analysis of the vegetation. The variation in the vegetation of the study area is interpreted in terms of one complex gradient representing a, series from relatively favourable to unfavourable for plant growth. Toxic effects of the substrates and water conditions are the main variables in this interpretation; the latter factor has a reversed effect on serpentine as compared to the non-serpentine substrates, and is less important than the toxicity factor. Comments are made on the table arrangement suggested by reciprocal averaging. The relatively favourable substrates were generally richer in species, but highest and lowest species numbers did not occur at the extremes of the interpreted gradient. The trend in the number of families per stand is similar to that in species numbers for the non-serpentine substrates, but is lowest in the badly-drained serpentine habitat interpreted as most unfavourable to plant growth. The species/family ratio per stand does not show much variation between any of the communities. The percentage of monocotyledonous species is strikingly higher in the communities on serpentine as compared to those in non-serpentine habitats. The total number of dominant species is not markedly different in the communities, but this means that dominant species are relatively more common in the floristically poorer communities of the serpentine, especially those with relatively high total cover values. Values for eveness and Simpson's index of heterogeneity calculated per stand largely confirm this. Again the number of monocotyledonous species amongst the dominants is surprisingly high in the communities on serpentine. Several suggestions explaining the relative success of monocotyledons in serpentine habitats are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 97 (1991), S. 11-20 
    ISSN: 1573-5052
    Keywords: Canopy ; Carbon gain ; Leaf area index ; Leaf nitrogen ; Light extinction coefficient ; Photosynthesis ; Structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The amount of photosynthetically-active photon flux density incident upon a leaf and the nitrogen content of that leaf strongly affect the photosynthetic carbon gain of that leaf. Therefore, the canopy structure of a stand, affecting the light climate in the canopy, and the leaf nitrogen distribution pattern in the canopy, affect the carbon gain of the whole canopy. This review discusses the results of studies directed to this problem and obtained so far in open and in dense canopies of stands of herbaceous, monocotyledonous or dicotyledonous, plants in their growing or flowering stages. It is found that the leaf nitrogen distribution pattern in the canopy is vertically non-uniform, and in dense stands more strongly so than in open stands. The leaf nitrogen distribution pattern in most canopies closely approaches an optimal pattern in that it maximizes whole canopy potential carbon gain as calculated for the actual total leaf nitrogen content and leaf area index of the stand. The resulting increase in potential carbon gain as compared to a uniform leaf nitrogen distribution pattern is considerable and it is larger in dense stands than in open stands. For at least some dense stands simulation studies show that with the available total leaf nitrogen content, whole canopy carbon gains could still be considerable higher had a lower leaf area index been developed.
    Type of Medium: Electronic Resource
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