Ordination of grassland and related communities in Otago
- Botany Department, University of Otago
This report forms part of a study of indigenous grasslands of Otago using continuum analysis. An attempt has been made to relate variation in grassland and related vegetation to the principal environmental gradients.
Stands were sampled throughout the grassland and related vegetation west of the coastal hills and east of the Cromwell Gorge. In each stand rapid point-records were taken to obtain relative values of cover for all macroscopic plants. Average relative values of ground cover for the leading physiognomic dominants and some prominent ground species are graphed for an arrangement of communities. These performance curves emphasize species optima and ranges of tolerance. The overlapping distributions indicate the continuum of vegetation along a gradient of increasing altitude and changing moisture.
Coefficients of dissimilarity between stands were computed as a partial matrix and these dissimilarity values formed the basis for the construction of a two-dimensional ordination using the method of Bray and Curtis.
The relationship between stand position and moisture and altitude is very marked. The ordination appears to be an adequate characterisation of the vegetation. Cover values for Bulbinella angustifolia, Raoulia subsericea, Anisotome flexuosa and Agropyron scabrum have been plotted and their distributions discussed.
From these preliminary results it is considered that ordination methods are of value in the presentation and analysis of causal relationships between indigenous grasslands, component species and their environments