The denominator changed in a pollen report

If recalculation raises the tree-pollen percentage in a sediment report, it may be described as vegetation change. Yet spores or aquatic plants may have been excluded from the pollen sum. Restore raw counts, inclusion categories and calculation rules for every layer before interpreting the pattern.

What needs to be clarified

Check whether the percentage diagram is reproducible, establish its denominator and distinguish relative proportions from evidence about pollen concentration in the sediment sample.

Materials to prepare

Raw taxon counts by sediment depth
Diagram workbook with formulas and exclusions
Preparation record with sediment volume and marker-grain data

What to compare

Recalculate the included categories for each layer, checking unidentified grains and matching depths. Compare percentages using documented denominator options. Separately check whether marker counts and sediment volume support concentration estimates, without substituting the number of grains examined on a slide.

Possible outcome of the analysis

A reproducible table may explain differences and exclusions, while identifying measures that cannot be calculated from the submitted observations.

Limits of the conclusions

A percentage change does not prove a change in absolute plant abundance. Transport modelling, dating and representative sampling are needed for confident local vegetation or source reconstruction.