You can estimate the age of a tree fairly quickly and accurately by measuring certain characteristics
Depending on the type of tree, the age of the tree can be estimated by, for example, measuring the circumference of the trunk or counting the rows of branches. However, the most accurate way is to calculate the circumference of the rings on the tree trunk. The bad thing is, this method can only be done if the tree trunk has been cut; You shouldn't cut down a healthy tree just to find out how old it is. We recommend that you try other methods or a combination of methods to get an accurate estimate.
Step
Method 1 of 4: Estimating Age by Measuring Tree Trunks
Step 1. Measure the circumference of the tree at chest height
The average chest height, which is a unit of measure in forestry, is 1.5 meters from ground level. Wrap a measuring tape around the tree trunk at this height, and record the circumference.
- If the ground is sloping, measure 1.5 meters from the ground level on the upstream side, mark it, then do the same thing on the downstream side. The mean chest height is the midpoint between the upstream and downstream sizes.
- For tree trunks that branch at a height of less than 1.5 meters, measure the circumference just below the branch.
Step 2. Find the diameter and radius of the tree trunk
To find the diameter, divide the circumference by pi, or 3, 14. Then find the radius by dividing the diameter by two.
For example, if the circumference of a tree trunk is 375 cm, its diameter is approximately 120 cm, and its radius is 60 cm
Step 3. Subtract by 0.5-2.5 cm to compensate for the bark
For tree species with thick bark, such as resin, reduce the radius of the tree by 2.5 cm. For species with thin skin (e.g. birch), subtract 0.5 cm. If you're in doubt and just want a rough estimate, reduce the radius by 1.5 cm.
If the bark is taken into account, your measurements will be redundant and inaccurate
Step 4. Use a nearly fallen tree to calculate the average width of the ring circumference
Try looking for dead or fallen trees in the vicinity of related trees (tree species must be the same). If you find a bar where the rings are clearly visible, measure the radius and count the number of rings. Then, divide the radius by the number of rings to find the average ring width.
- Say there is a stump near a related tree that is 65 cm in radius, and has 125 rings. The average ring width is 0.5 cm.
- Tree growth rates vary widely, depending on the species and environmental conditions. The living tree being measured may grow at a rate similar to that of a tree of the same species growing nearby.
- You'll use a number of ring circumference widths, or the average growth rate if there are no stumps near the associated tree, to plug into the equation and estimate the tree's age.
- Even if you get the average ring width, you can also use the growth rate to estimate the age of the tree, and then compare the results of the two methods.
Step 5. Find the average growth rate of the species, if necessary
If you can't find a stump or fallen tree, look up the average tree species growth rate measured online. Include the location in the search for more accurate results.
- For example, the circumference of an oak, fig and sycamore tree grows about 1.5-2 cm per year. If you don't know the species, plug 1.5 cm and 2 cm into the equation to estimate the age range.
- For a more accurate estimate, consider the location of the tree. In an open environment, the growth rate is usually greater, or 2-2.5 cm per year. Growth tends to be slower in residential areas and dense forests.
- Be sure to check out how to calculate growth rates. Many sources base growth rates on the number of tree widths or circumferences per year. However, you can find a rate based on the average ring width of the radius.
Step 6. Divide the radius by the average ring width
If you are using a stump near a tree to calculate the average ring width, divide the radius of the live tree by the average ring width.
- Say, the tree has a radius of 60 cm after the bark is removed. Using tree stumps of the same species, you get an average ring width of 0.5 cm.
- Divide 60 cm by 0.5 cm to determine the estimated age of the tree as 120 years.
Step 7. Divide the circumference by the average annual growth rate
If you're getting an average growth rate by thickness, or circumference, divide the tree's circumference by its annual growth rate.
Say the circumference of the tree is 390 cm, and and the growth rate is between 2-2.5 cm per year, then divide 390 cm by 2.5 cm. The estimated age range will be between 154 and 205 years
Method 2 of 4: Calculating the Threaded Branch Circumference
Step 1. Calculate the thread circumference to estimate the age of the conifers
The ring of threads is a row of branches that grow from the stem at approximately the same height. You can calculate the thread circumference to calculate the age of conifers, or evergreen trees, but it's not very useful for broadleaf trees, such as oaks or sycamores. This method is not as accurate as calculating the ring circumference of a tree, but it can be tried to estimate the age without cutting or injuring the tree.
- Conifers grow thread rings annually at regular intervals. Deciduous plants, or broadleaf trees, grow thread rings so irregularly that it is difficult to calculate them accurately.
- In addition, the thread circumference of young conifers is easier to calculate. You may not be able to see the tops of mature, tall conifers, and there may be more irregularity in their growth patterns.
Step 2. Count from the branches growing at the same height
At the base of the tree, look for a row of branches growing at the same height, the trunk without branches, then another row of branches. This row is the circumference of the thread, which you need to calculate until it reaches the top of the tree.
You can see a single branch growing between the thread loops or 2 thread loops that are slightly close together. These irregularities can indicate injuries or odd weather conditions of the year so they should be counted
Step 3. Include all the stump and knots at the bottom of the trunk
Check under the first row of branches to find evidence of previous growth. Look for the stump on the trunk where the branch once grew, which will count as additional thread circumference.
For example, say you can see a tree has 8 thread loops. Below the first row, you can see several weevil emerging from the tree trunk at approximately the same height. There is also a row of 2-3 knots under the hump. Thus, the studs and knots will be counted as additional thread circumference so that the total calculated is 10
Step 4. Add 2-4 years to compensate for seedling growth
The tree germinates and grows as a seed for several years before growing a woody thread ring. Add 2-4 to the thread circumference count to account for this initial growth.
If the calculated thread circumference is 10, the estimated final age is between 12-14 years
Method 3 of 4: Calculating the Circumference of the Stump Ring
Step 1. Check the ring circumference on the exposed stump
The number of rings on the stump indicates how many years the tree has lived. You will see dark rings, and lighter ones; one year of growth consists of dark and bright rings. Since they are difficult to distinguish, count the dark rings to estimate the age of the tree.
Tree rings will also indicate environmental conditions in a given year. Thin rings indicate cooler or drier years, and thick rings indicate better-than-normal tree growing conditions
Step 2. Rub the stump with sandpaper to define the circumference of the ring
If the ring of the tree is hard to see, first buff it with 60 grit sandpaper. Finish with fine sandpaper, such as 400 grit. Spray the surface of the stump with a little water to make it easier to see.
You may also find that some of the rings are so close together that they are difficult to distinguish clearly. If necessary, use a magnifying glass
Step 3. Count the rings from the core (center) of the tree trunk
Find the core, or small circle in the center of the stump. Start counting from the circumference of the first very dark ring around the core. Keep counting until you reach the skin. The last ring is the one pressed against the skin and hard to see so make sure not to miss it.
If you're having trouble counting, try writing a number or sign for every 10 rings with a pencil
Method 4 of 4: Counting Rings on Core Samples
Step 1. Take a live tree core sample using the increment borer tool
To be able to estimate the age of a tree without killing it, use the increment borer tool to sample. An increment driller is a Y-shaped tool consisting of a drill bit and an extractor, which is attached to the drill. The T-shaped end is the handle, which is turned to insert and remove the drill from the tree.
The length of this tool should be at least 75% of the diameter of the tree. You can find increment borers online and at forestry supply stores
Step 2. Drill the trunk at chest height
Measure the tree trunk 1.5 cm from the ground level. Position the drill bit at that height in the center of the tree trunk.
- Sampling at chest height allows you to estimate something called DBH age. You will need to add 5-10 years to the age of the DBH to estimate the total tree age.
- You will need to sample at chest height as it is impossible to sample from the base of the tree. Roots and soil will prevent you from turning the handle, and drilling is difficult while crouching or lying on the ground.
Step 3. Drill past the approximate midpoint of the tree
Press firmly and turn the handle clockwise to drill into the tree trunk. Continue turning until you've drilled approximately 5-7.5 cm through the core, or center of the trunk.
Calculate the trunk radius to estimate how far you will need to drill. Measure the circumference of the tree, divide by pi (3, 14) to find the diameter, then divide by 2 to get the radius
Step 4. Insert the extractor, then turn the handle counterclockwise
The extractor is a long cylinder with teeth at the end. This part is fitted to a drill, or part that is drilled into a tree. Insert the extractor, then turn the handle clockwise to release the tool and remove the core sample.
Step 5. Take the sample out and find the core, or center of the tree trunk
After removing the sample from the extractor, you will see a row of concentric curved lines. These are the parts of the tree ring circumference. You will see a point at the interior end (as opposed to the bark portion) of the core sample that marks the midpoint of the circumference of the concentric rings.
If you don't see the gist, place the sample on a large sheet of paper, and extend the curve to make a full circle on the paper. Based on the rings drawn, you can guess the midpoint of the tree, and estimate how many rings have been missed
Step 6. Count the number of rings in the core sample
Once you've found the core at the interior end of the sample, count dark curved lines until it reaches the end of the sample bark. Use a magnifying glass if you have trouble counting curved lines that are close together.
- If you're still having trouble counting the curved lines, rub the sample with sandpaper until it's clear. Start with 60 grit sandpaper, then finish with a fine grit paper, for example 400.
- Note that the ring only provides an estimate of the age of the DBH. Add 5-10 years to estimate the tree's total age.
Tips
- Tropical trees usually don't have an obvious ring circumference, so you'll need to use other methods to estimate tree age in locations without winter.
- While ring counting is still the most accurate of all methods, it's not 100% accurate. Weather conditions, soil conditions, damage to trees, and other factors can cause a tree to produce several rings a year, or none at all.
- Taking a sample will damage the tree, but the tree will heal itself. There are fungicidal compounds designed to speed up the healing of trees. However, this product can also trigger infection so you should not use it.
Warning
- Use a drill, saw, or other sharp object with care.
- Don't cut down healthy trees just to find out how old they are.
