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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 37 (1978), S. 129-140 
    ISSN: 1573-5052
    Keywords: Bray-Curtis ; Coenocline ; Components analysis ; Non-linear ; Ordination ; Polynomial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recent studies suggest problems resulting from using essentially linear ordination techniques on non-linear ecological data. A new non-linear method, termed polynomial ordination, was developed in response to these problems. Its effectiveness was compared to that of two standard techniques, Bray-Curtis ordination and principal components analysis, by testing with both simulated and field data. The original species axes are resolved into their principal components. If significant curvilinear relationships between principal components are present, new axes are defined along these curves. The coordinates of positions of the sample points along the axes are then determined. Using simulated data, the coordinates of the sample points on the first axis were compared to their coordinates on the original simulated gradient. Two statistics were used to evaluate how well the gradient was recovered. Of the methods tested, polynomial ordination best placed the samples in the correct order, although principal components analysis better recovered their absolute positions. Ordinations of vegetation samples along a Sonoran Desert bajada by all three methods suggested that soil particle size is a major environmental gradient affecting the species composition of the vegetation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant ecology 80 (1989), S. 25-35 
    ISSN: 1573-5052
    Keywords: Arenaria ; Competitive release ; Dominance shift ; Drought ; Sedum ; Senecio ; Southeastern USA ; Viguiera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Permanent quadrats in granite outcrop plant communities allowed us to monitor seasonal variation and annual fluctuation in community structure. Seasonal species turn-over was significant in communities on shallow soil, but not in communities on deeper soil where seasonal dominance shifts were common. Exceptional meteorological events appeared to mediate phenomena of competitive release in some island communities. A decrease in the abundance of Arenaria uniflora in Lichen-annual island communities, following a spring drought, was correlated with an increase in the abundance of Sedum smallii, a shallower-soil species. Richness in Annual-perennial island communities was higher in spring 1985 than in 1984 or 1986, and this occurred as the dominant species, Senecio tomentosus, temporarily declined in importance following a severe drought in late summer 1984. Significant annual fluctuation in the cover of Viguiera porteri could also be related to variations in the summer precipitation regime. Overall, plant responses to drought were individualistic and depended largely on the timing of these meteorological events in relation to the life-stages and/or the physiological status of the plants.
    Type of Medium: Electronic Resource
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