11.6: Dendrochronology

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Dendrochronology is a process used to determine the order and timing (chronology) of events using information in tree rings (dendro- refers to trees). These rings form in response to environmental conditions, storing information on climate and historic occurrence of fires in an area. Essentially, you bore a hole into a living tree and extract a thin section column of the wood. This becomes your reference specimen, as you date each annual ring, tracing back from the present date. Your reference specimen can then be used to determine the timing of events in dead trees, potentially tracing back thousands of years.

Imagine that the sample below is from your reference specimen. The example core shows features you might see in a tree core and how to interpret them.

Figure \(\PageIndex{1}\): Tree core example and reference specimen

How old is this tree? At which dates did rainy years occur? Which periods represent droughts? When did fires occur? Make notes on the annual rings with the date and notable events.

Figure \(\PageIndex{2}\): Dead tree cores

Using your reference specimen, date the events in the following dead trees of unknown age from the same forest. It will be easiest to do this by cutting out each core and aligning it next to the reference. There is no text on the bottom of this page on the opposite side, so cut away!

Based on the dendrochronology you just performed, what did you determine about the history of this forest and climate in this region? Be as specific as possible in your answer.

What is the oldest date that you calculated on the tree core present?

Contributors and Attributions

Maria Morrow (College of the Redwoods)