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  • Vegetation structure  (2)
  • Aloe  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Plant ecology 53 (1983), S. 161-178 
    ISSN: 1573-5052
    Schlagwort(e): Afromontane forest ; Cape fynbos ; Endemism ; Gradient analysis ; Growth forms ; Phytochorological affinities ; Soil moisture ; Soil nutrients ; Subtropical thicket ; Vegetation history ; Vegetation structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Patterns in the relative importance of structural attributes and growth forms along fynbos and non-fynbos coenoclines were studied to test the hypothesis that there would be less structural variation in the former because the overriding influence of low levels of soil nutrients would be manifest in a great deal of structural convergence in fynbos. The coenoclines were ranged along identical environmental gradients of increasing altitude, rainfall and soil moisture and decreasing climatic variability. Results showed that along the entire fynbos coenocline vegetation was structurally a small-leaved sclerophyllous shrubland with a graminoid understorey and, usually, a large-leaved (proteoid) shrub overstorey. Fynbos structure was interpreted largely as a response to low levels of soil nutrients. Non-fynbos vegetation ranged from mixed succulent-sclerophyllous and spiny large-leaved thicket at lower altitudes to tall mesic forest at the upper end of the gradient. Non-fynbos structure was explained in terms of variations in soil moisture and climate. An analysis of the biogeographical affinities of sample floras at sites along the coenoclines showed that fynbos vegetation was dominated by taxa endemic to the Cape phytochorion, although phytochorological mixing was pronounced at the lower altitude sites. The level of local endemism in the fynbos coenocline was relatively high; nearly all endemics were Cape fynbos taxa and their incidence increased with increasing altitude. These data indicate that fynbos vegetation has had a lengthy history in the southeastern Cape and that high altitude sites would have comprised a refuge for Cape taxa during unfavourable climatic periods. Non-fynbos vegetation ranged from dry subtropical Tongaland-Pondoland thicket with a strong Karoo-Namib component to temperate Afromontane forest. Levels of endemism were lower than the fynbos coenocline and decreased with increasing altitude. The high number of karroid endemics found in both coenoclines at low altitudes suggests that karroid vegetation would have been more widespread in the past, probably during the last glacial which was considerably drier than the present Holocene interglacial.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Plant ecology 43 (1980), S. 191-197 
    ISSN: 1573-5052
    Schlagwort(e): California ; Cape Province ; Chile ; Convergence ; Edaphic factors ; Mediterranean climate ; South Africa ; Speeies richness ; Vegetation structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Plant communities on desert to montane transects in the mediterranean type climatic areas in southern California, central Chile and the Cape, South Africa have been analysed to determine the extent of vegetation convergence. Data on floristic richness, growth form, leaf duration, leaf size, and spineseence, of the woody plants, collected by Parsons & Moldenke (1975) from analogous climatic sites in California and Chile, were compared with data from analogous sites in the Cape. Considerable convergence in vegetation structure between floristically distinct but climatically similar sites in California and Chile has been demonstrated by Parsons & Moldenke (1975). Cape vegetation, however, shows little convergence to these mediterranean regions. In Cape desert communities succulence rather than drought deciduousness is the principal adaptive strategy. Cape fynbos communities show major differences from communities at analogous sites on the other continents. Much of the divergence between fynbos and the vegetation of the other continents can be attributed to the nutrient-poor soils on which fynbos has evolved.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 1572-9710
    Schlagwort(e): demography ; succulents ; Western Cape ; Aloe ; Pachypodium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Arborescent succulents are conspicuous elements of the arid flora of the far north-western Cape Province. In the Richtersveld and two adjacent more southerly areas (Springbok and Nieuwoudtville), we surveyed the population structure of the following three species, Pachypodium namaquanum (Apocynaceae), Aloe dichotoma and A. pillansii (a rare endemic) (both Liliaceae). Only in the Richtersveld, did both Aloe species have a high proportion of dead individuals and all three species had few seedlings there. Populations in adjacent areas had lower levels of mortality and greater recruitment. Mortality appears to be due to damage by baboons and porcupines. This apparent decline is potentially serious because all three species appear to be keystone species. They supply perches to raptors, nesting sites for other birds, nectar for birds, and food, habitat and moisture to other animals.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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