Reading a pollen diagram: a beginner's guide
Those spiky charts of curves are timelines of ancient forests. Here's how to read one.
Open any Quaternary paper and you will meet a pollen diagram: a wall of curves that looks intimidating and is actually a straightforward timeline. Here is how to read it.
Depth is time
The vertical axis is depth in a core — and because sediment piles up over time, depth is age: deeper is older. Each column across the diagram is one plant type, showing how common its pollen was at each level.
Trees vs open ground
A quick first read is the balance of arboreal pollen (AP), from trees, against non-arboreal pollen (NAP), from grasses and herbs. A swing toward AP usually means forests spreading as the climate warmed; a swing to NAP means open, cooler or human-cleared landscapes.
Zones and events
Where the assemblage stays stable, researchers define a pollen zone; where it shifts sharply, something happened — warming, fire, or the arrival of farming (watch for cereal pollen and weeds). The technique goes back to Lennart von Post, who drew the first such diagrams in 1916.
Want the full method? Read our guide to pollen & climate.