QUB | Archaeology and Palaeoecology | The 14Chrono Centre
1 Rarefaction analysis (off) [off] Enter '0' for on, or '1' for offIt is a matter of common observation that different pollen spectra have different numbers of pollen types, but it is also obvious that the number of taxa must have some relation to the number of pollen grains counted, and this number is never constant from one sample to another. Rarefaction analysis (introduced to pollen analysis by Birks & Line [1992]) provides a way of determining the palynological richness of a given pollen spectrum if a certain other number of grains had been counted (which must be less than the actual number counted). The pollen count is thus effectively standardized to a single sum, and it is then possible to compare the richness between samples. If the size of standardized count is kept constant between sequences, and other conditions hold (similarity of pollen taxonomy between analysts, for example), then it may be possible to compare richness between sequences.
In order to use this option, the main input file must:
Specify the count size for standardization [0] Enter number <Enter>The default value is the lowest pollen sum in the dataset. Otherwise, 250 is a good number, and should be achievable for all datasets.
Results are available for immediate plotting, and will be included with the rest of the dataset for saving to the data analysis file (menu J). If samples are marked for skipping, the results for those samples are set as -1. When plotted, the curve will be joined up across them, or a break left, depending on the setting of menu Df.
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