Current problems of environmental gradients and species response curves in relation to continuum theory

Abstract. Comparisons of the positions of species on Grimes'C-S-R triangular ordination model with their responses to individual environmental gradients indicates that the C-S-R model does not necessarily predict species ecological behaviour. The importance of the stress, productivity and disturbance gradients relative to other environmental gradients needs to be determined. In studies of species behaviour along a biomass/productivity gradient the collective vegetation property, biomass, has been confused with the environmental factor, fertility. Patterns of responses to biomass gradients e.g. Keddy's centrifugal model, should be examined in a two-dimensional environmental space to avoid such confounding effects. Assumptions regarding the shapes of species responses to environmental gradients remain untested. A recent model of species response functions to environmental gradients suggested that skewed responses curves show a pattern in the direction of the skew, always with the tail towards the presumed most mesic position on the gradient. Further evidence is presented to support this model for a temperature gradient in eucalypt forest in south-eastern Australia. 21 out of 24 species tested conform to the model.

[1]  Bill Shipley,et al.  The individualistic and community-unit concepts as falsifiable hypotheses , 1987 .

[2]  T. M. Smith,et al.  A new model for the continuum concept , 1989 .

[3]  Paul A. Keddy,et al.  13 – Competitive Hierarchies and Centrifugal Organization in Plant Communities , 1990 .

[4]  C. Braak.  Canonical Correspondence Analysis: A New Eigenvector Technique for Multivariate Direct Gradient Analysis , 1986 .

[5]  Mike P. Austin.  Searching for a Model for Use in Vegetation Analysis , 1980 .

[6]  Paul A. Keddy,et al.  Beyond reductionism and scholasticism in plant community ecology , 1987 .

[7]  Paul A. Keddy,et al.  Assembly and response rules: two goals for predictive community ecology , 1992 .

[8]  J. Leathwick,et al.  Forest pattern, climate and vulcanism in central North Island, New Zealand , 1992 .

[9]  P. Keddy,et al.  Competition and centrifugal organization of plant communities: theory and tests , 1992 .

[10]  J. P. Grime,et al.  A QUANTITATIVE ANALYSIS OF SHOOT PHENOLOGY AND DOMINANCE IN HERBACEOUS VEGETATION , 1977 .

[11]  P. Keddy,et al.  Species richness, survivorship, and biomass accumulation along an environmemtal gradient , 1988 .

[12]  I. Prentice,et al.  Theory and models in vegetation science , 1987, Advances in vegetation science.

[13]  Mike P. Austin,et al.  Continuum Concept, Ordination Methods, and Niche Theory , 1985 .

[14]  R. H. Økland.  Studies in SE Fennoscandian mires: relevance to ecological theory , 1992 .

[15]  Mike P. Austin,et al.  Models for the analysis of species’ response to environmental gradients , 1987 .

[16]  A. O. Nicholls,et al.  Measurement of the realized qualitative niche: environmental niches of five Eucalyptus species , 1990 .

[17]  M. Austin.  Modelling the Environmental Niche of Plants: Implications for Plant Community Response to Elevated CO2 Levels. , 1992 .

[18]  P. Keddy,et al.  Conservation of wetlands: do infertile wetlands deserve a higher priority? , 1989 .

[19]  C.J.F. ter Braak,et al.  The analysis of vegetation-environment relationships by canonical correspondence analysis , 1987 .

[20]  R. Leemans,et al.  Pattern and process and the dynamics of forest structure: a simulation approach. , 1990 .

[21]  M. Austin,et al.  USE OF A RELATIVE PHYSIOLOGICAL PERFORMANCE VALUE IN THE PREDICTION OF PERFORMANCE IN MULTISPECIES MIXTURES FROM MONOCULTURE PERFORMANCE , 1982 .

[22]  Relations between community theory and community analysis in vegetation science: some historical perspectives , 1987 .

[23]  S. Pickett,et al.  Organization of an Assemblage of Early Successional Species on a Soil Moisture Gradient , 1978 .

[24]  E. Ranta,et al.  Plant strategies along mountain vegetation gradients: a test of two theories , 1992 .

[25]  C. Braak.  Correspondence Analysis of Incidence and Abundance Data:Properties in Terms of a Unimodal Response Model , 1985 .

[26]  T. Yee,et al.  Generalized additive models in plant ecology , 1991 .

[27]  P. Keddy,et al.  Species richness – standing crop relationships along four lakeshore gradients: constraints on the general model , 1989 .

[28]  P. Keddy,et al.  Centrifugal organization in forests , 1990 .

[29]  A. O. Nicholls,et al.  Determining species response functions to an environmental gradient by means of a β‐function , 1994 .

[30]  M. Austin,et al.  Community theory and competition in vegetation. , 1990 .