Tree Age Calculation – 3 Official Methods
The Government of Maharashtra has prescribed three primary methods to determine the age of a tree. These methods are scientific, documentary-based, and evidence-based.
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Method 1 – Determining Tree Age Based on Written Records or Witness Statements
1. If written records are available:
If the year of plantation, registry, maps or any official written documents are available, the age of the tree can be determined directly from those records.
2. If written records are not available:
If no written documents exist, the estimated age of the tree is determined by recording the sworn statements of local witnesses who have knowledge about the tree.
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Method 2 – How to Calculate Tree Age Using the Growth-Factor Method?
This method requires two things:
1️⃣ Circumference of the tree
2️⃣ Growth factor of that species
The growth factor is the average yearly growth rate of a particular tree species.
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🧮 Three Simple Steps to Calculate Tree Age
1) Measure the tree circumference
Measure the circumference in inches using a tape at about 4.5 feet (1.37 m) above the ground.
Example:
Tree Circumference = 20 inches
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2) Convert circumference to diameter
Using the formula:
Diameter = Circumference ÷ 3.14
For the above example:
Diameter = 20 ÷ 3.14 = 6.36 inches
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3) Multiply the diameter by the growth factor
Tree Age = Diameter × Growth Factor
If the growth factor = 3.0 (e.g., for Teak the factor is approx. 3.03)
Then,
Tree Age = 6.36 × 3 = 19.08 ≈ 19 years
Thus, the estimated age of the tree is 19 years.
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What exactly is a growth factor?
Each tree species grows at a different rate.
Some grow 1 inch per year, some 0.5 inch, while others may grow 2 inches per year.
This average annual growth rate is known as the growth factor.
Example (Species – Growth Factor):
Species Growth Factor
Teak 3.03
Sal 7.47
A higher growth factor (like in Sal) means the species grows slower; therefore, even a smaller diameter may indicate a higher age.
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Method 3 – Tree Age Determination Using an Increment Borer
Among the scientific techniques used to determine tree age, the Increment Borer method is one of the most accurate. It involves collecting a core sample from the trunk and studying the annual growth rings.
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How this method works
An Increment Borer is a special tool used to extract a very thin wooden core from inside the trunk.
This core clearly shows the annual rings.
The age of the tree is determined by counting these rings.
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Important Government Instructions
Since this method requires technical skill, the Government has issued clear directions:
✔ Until the technical expertise of the Local Tree Authority is fully developed,
✔ This procedure must be carried out only under the supervision of trained Forest Officers.
This means that only trained and authorised personnel should use an Increment Borer.
Untrained use can cause unnecessary damage to the tree.
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Method 3 is a highly scientific and precision-based technique, but because it needs specialised training, it must currently be performed only under the supervision of Forest Department experts.
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FAQ – How Is Tree Age Determined?
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1) How is the age of a tree determined? What are the official methods?
The Government of Maharashtra recognises three official methods:
1. Written records or witness statements
2. Growth factor (Growth-Factor Method)
3. Increment Borer core-sample method
These methods are scientific, documentary-based, and evidence-based.
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2) What is a growth factor and how is it used to calculate tree age?
A growth factor represents the average annual growth rate of a tree species.
Steps:
– Measure circumference in inches
– Divide by 3.14 to calculate diameter
– Multiply diameter by the species-specific growth factor
The result is the estimated age of the tree.
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3) What is an Increment Borer? How does it help determine tree age?
An Increment Borer is a scientific tool used to extract a thin wooden core from the tree.
The core shows annual growth rings.
Counting these rings gives the exact age of the tree.
It is considered the most accurate method.
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4) Can the Increment Borer method be used by the general public?
No.
The government has clearly stated that this new and technical method should be used only by trained personnel or under the supervision of Forest Officers.
Using it without training may damage the tree.
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5) How is tree age determined when no written records are available?
If plantation records or other documents are not available, the tree's estimated age can be determined using sworn witness statements from locals familiar with the tree.
This method is government-approved and legally valid.
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