Collecting tree data

Once the hectare plot has been subdivided into quadrats, researchers start collecting data on the trees. This includes measuring and tagging trees as well as recording tree status, mapping tree location and identifying species.

Measuring trees

A standard measurement for collecting data on forest biodiversity is recording the trunk's diameter at breast height (DBH). The DBH is standardised at 1.3 metres.

At 1.3 metres from the base of the tree, a researcher marks the trunk with a small scratch and a spot of red paint. This mark ensures that the same point of measurement can be used in the future for a re-census. Plots are re-censused every five years to collect information on tree growth and mortality rates.

Researchers mark tree trunks that have a DBH of either ten centimetres or more, or four centimetres or more.

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Tagging trees

Each marked tree is tagged with plastic-covered wire and a tag on the side of its trunk. Each tag has a numbering system unique to that tree.

On each tag, there are three pairs of numbers.

The first pair is the plot number. For example, in the first one-hectare plot, the numbers would be 01.
The second pair is the quadrat number. There are 25 quadrats in each hectare. The first quadrat would be numbered 01. The second quadrat would be 02.
The third pair of numbers represents the tree itself. These will start with 01 and continue until all trees in that quadrat have been counted. For example, for the first tree in the first quadrat of plot 1, the tag will read '01 01 01'. The tag for the fifth tree in the second quadrat will read '01 02 05' and so on.

You can participate in tagging trees in an online activity.

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Status of trees

Next, researchers record the height and status of individual trees. The height can be estimated or calculated. A coding system is used for recording each tree's status.

AS alive standing
AL alive leaning
AB alive broken
AF alive fallen
DS dead standing
DL dead leaning
DB dead broken
DF dead fallen
NL not located (this is used only in a re-census)

You can participate in coding tree status in an online activity.

Mapping and identification

Each tree is mapped in relation to all other trees. A representative of each species in the plot is collected. These specimens are used to verify the identity of all the species present in the plot.

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