Horrocks & Ogden-Interpretation of fossil pollen assemblages

New Zealand Journal of Botany abstracts

An assessment of linear discriminant function analysis as a method of interpreting fossil pollen assemblages

M. Horrocks

Centre for Archaeological Research, and School of Geography and Environmental Sciences
University of Auckland
Private Bag 92-019
Auckland, New Zealand

J. Ogden

School of Geography and Environmental Sciences
University of Auckland
Private Bag 92-019
Auckland, New Zealand

Abstract Linear discriminant function analysis (LDF) is assessed as a method of interpreting fossil pollen assemblages from Mt Hauhungatahi, Tongariro National Park, and Ohakune-Horopito, central North Island, New Zealand. Pollen types selected by stepwise discriminant analysis were used in LDF to predict the vegetation type (forest, dense scrub, open fernland, or open tussockland) and canopy type (closed or open) represented by fossil pollen assemblages from an array of sites. Chi-square Goodness-of-fit tests were used to test prediction made by LDF against the vegetation type suggested by the common “standard” method of assessment of the fossil pollen spectra, which is carried out by visual inspection of stratigraphic pollen diagrams. Some sites showed highly significant differences, with many samples obviously misclassified by LDF, especially those from montane forest vegetation. This misclassification occurred mainly because the montane forest samples were so different from the remainder that they were excluded from the prediction set, so that the pollen types most likely to be predictors were not employed. Overall, however, more sites showed no significant differences. The LDF method is confirmatory rather than providing a clear improvement, and its validity will depend strongly on the correct choice of discriminators.

Keywords palynology; stepwise discriminant analysis; linear discriminant function analysis

B02039 Received 20 May 2002; accepted 4 December 2002; published 11 June 2003
New Zealand Journal of Botany, 2003, Vol. 41: 293-299
0028-825X/03/4102-0293 $7.00 © The Royal Society of New Zealand 2003

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