3.
Interpreting and presenting the results
To interpret the results and work out
the story, you need to know how to ‘read’ a
pollen diagram. Pollen diagrams are really just a lot
of graphs put side-by-side
Summary curves for Greenhead Moss
Trees, shrubs, heaths, herbs, ferns versus depth with
dates alongside plus stratigraphy
The y-axis
is depth, with the base of the core at the bottom and
the surface at the top. Because peat builds upwards
through time, this is directly related to age. To
work out how old bogs are, we use the ‘carbon
clock’ in dead organisms making up the peat.
How a bog grows
The carbon clock: dating peat
The x-axis is made up of a series
of curves, one for each type of pollen or plant.
Changes in the curves show us how the percentage of
each plant changed through depth and time.
More details
the three stages of pollen work
www.shef.ac.uk/~ap/pollen/contents.html
Reading backwards: a few
technicalities!
We know that the plants growing in the
past produced the pollen we find in peat, but you
need to know a bit more detail to read from the
pollen back to the plants.
1. Pollen percentages in the
pollen diagram aren’t exactly the same as the
percentage of each plant in the vegetation, because
some plants produce lots of pollen, while others
rmake or release very little. Imagine one hazel shrub
compared with one herb plant, like a ransom (a
relative of wild garlic) growing underneath the tree:
the hazel has lots of branches and many flowers,
compared with the small number of flowers on each
ransom plant. Palyologists understand this and take
it into account when they are interpreting pollen
diagrams.
Ramsons under hazel shrubs © SNH
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