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  • 1
    Electronic Resource
    Electronic Resource
    A new model for the continuum concept (1989)
    Springer
    Plant ecology 83 (1989), S. 35-47 
    Details
    ISSN: 1573-5052
    Keywords: Environmental gradient ; Fundamental niche ; Niche theory ; Realized niche ; Species response curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A reformulation of the continuum concept is presented after considering the implications of the community/continuum controversy and current niche theory. Community is a spatial concept dependent on landscape pattern while the continuum is an environmental concept referring to an abstract space. When applying niche theory to plants, the mechanisms of competition are ill-defined and the assumption of bell-shaped response curves for species unrealistic. Eight testable propositions on the pattern of response of vegetation to environmental gradients are presented 1. Environmental gradients are of two types. a) resource gradients or b) direct physiological gradients. 2. The fundamental niche response of species to resource gradients is a series of similar nested response curves. 3. The fundamental niche response of species to direct gradients is a series of separate, independent, overlapping response curves. 4. Species fundamental response curves are such that they have a relative performance advantage in some part of the environmental space. 5. The shape of the realized niche is variable even bimodal but predictable from the fundamental response given the other species present. Propositions 6–8 describe the response shapes of emergent community properties to environmental gradient; species richness is bimodal, dominance trimodal and standing crop unimodal. Detailed comparisons of these propositions are made with the alternative theories of Ellenberg, Gauch and Whittaker, Grime, and Tilman. These theories are incomplete lacking several generally accepted properties of plants and vegetation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00031679
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    New approaches to direct gradient analysis using environmental scalars and statistical curve-fitting procedures (1984)
    Springer
    Plant ecology 55 (1984), S. 11-27 
    Details
    ISSN: 1573-5052
    Keywords: Aspect ; Australia ; Direct gradient analysis (DGA) ; Environmental scalar ; Eucalypt ; Generalized Linear Modelling (GLM) ; Radiation index ; Realized niche ; Species response curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The conceptual framework of direct gradient analysis (DGA) is discussed in relation to the functional, factorial approach to vegetation. Both approaches use abstract simplified environment gradients with which to correlate vegetation response. Environmental scalars based on physical process models of environment and/or known biological growth processes can be incorporated to make analyses less location specific. An example of an environmental scalar (radiation index) for converting aspect and slope measurements to the more biologically relevant radiation input at a site is given. The problem of the shape of species response curves to environmental gradients is examined using a sample of 1 286 plots from eucalypt forest in southern New South Wales. An important conclusion is that skewed or bimodal response curves may be due to unsatisfactory distribution of observations and/or unrecognized environmental factors. The use of Generalized Linear Modelling (GLM) as a method for providing a statistical basis for DGA is presented. Analyses using GLM, and presence/absence data are presented for a range of eucalypt species (Eucalyptus rossii, E. dalrympleana, E. fastigata etc.). Successful prediction of species distributions (realized niches) can be achieved with mean annual temperature, mean annual rainfall, radiation index and geology. Quadratic terms are required in many cases, indicating bell-shaped response curves. The major variability associated with species niches is shown to be related to a limited number (4) of environmental factors. DGA with biologically relevant scalars and appropriate statistical methods is suitable for studying many problems of species' realized niches and plant community composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039976
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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