Dendrochronology: Determining a tree’s age

Dendrochronology: Quick Facts

What?

Collecting data from the growth rings formed in trees. Data can help determine the different climates found in those areas previously, and the age of the trees.

Why?

Learning about the environmental changes through history allows a comparison between today's climates, with previous climates. We can see the effect humans are having on the environment, versus climate changes that happened naturally. Dendrochronology can also help age discovered wooden artefacts found in old buildings.   

How?

To access tree rings, trees must be felled. Scientists can analyse growth rings - the amount and shape of the rings, and compare them to previous data, looking for patterns to determine the environmental changes in the area. 

What is Dendrochronology?

Dendrochronology includes the study of growth tree rings. The rings determine the age of the tree, and different environmental changes experienced. Scientists look for differences in ring sizes, the distance between rings, and the number of rings present. 

In each year of growth, trees create a new ring that reflects the weather conditions of that season. A single tree can give us a small indication of the environmental conditions in a specific year of tree growth, along with the age of the tree at felling. However, collecting hundreds and thousands of tree-ring data, and comparing them against each other, can help build a database. This provides us with a database as a comparison when exploring climate changes.

tree rings

Why is dendrochronology useful? 

Dendrochronology allows scientists to recognise patterns in climate changes by seeing growth changes in the trees growth rings. This helps to build a picture of weather patterns the area has seen throughout history, and the changes this caused to trees and the surrounding wildlife, and how they acclimatise to those conditions.  

Scientists can also determine how old the trees are, and how much carbon is stored within the tree. They can create a database comparing the information for different aged tree species. They can then compare this data to wooden artefacts found within buildings, to determine the age they created the artefacts. 

By discovering past environmental changes and patterns, can help to predict future environmental changes that we may expect to see. 

Is Dendrochronology a reliable method of aging trees?

Most of the time, dendrochronology is a reliable method to determine tree age and environmental changes. However, the method assumes that for every year of growth, a ring forms. This theory has been tested on different species of trees, and some seem to be more reliable than others. The oak, for example, seems to be very reliable in that tree rings have been noted for every year of growth. On the other hand, Alder and Pine sometimes were missing growth rings, or rings have doubled up in the same year which affects the reliability of the data. Overall though, dendrochronology seems to give us useful data which when compared to the actual known age of the tree, appears to be reliable most of the time.  

How can the age of wood be discovered through radiocarbon dating?

Radiocarbon dating is when dendrochronology data is used to work out the date that the growth ring within the tree was created, by measuring the amount of carbon in the tree sample. The amount of radiocarbon-14 isotope present within the sample is compared against existing tree ring data. They always calibrate data against organic material of known age, for a more accurate finding.

Although it is difficult to determine the exact age of some artefacts, comparing existing data collected from trees both with a known age, and the database gathered through dendrochronology is thought to be accurate.  If the artefact has the exact same amount of carbon isotope, as a previously recorded sample, this would suggest they are of the same age.  To allow for any discrepancies, radiocarbon dates come with an error factor of a certain amount of years.  For example +/- 20 years.  

Can we determine the age of trees without felling them?

Whilst it is possible to fell some trees to determine their age, it wouldn't be very environmentally friendly to eradicate all trees within a forest to gather data to compare.  Fortunately, there are ways of estimating tree age without the need to fell them.  You can check out our post regarding this here: 

Sources:

https://www.environmentalscience.org/dendrochronology-tree-rings-tell-us

https://www.sciencedirect.com/topics/earth-and-planetary-sciences/dendrochronology

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Lauren


Lauren

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