Dendrochronology

How to determine the age of a tree

Following a few easy matematical calculations you can estimate the age of any large tree. You will need a few materials: diameter tape to calculate the radius of the tree, increment borrer to retrieve a core sample and a metric ruler. It is not necessary to core to the heart of the tree.

  1. After measuring the DBH and obtaining a core sample:
  2. Divide the DBH by 2 to find the radius of the tree.
  3. Measure the length of the core sample (cm).
  4. Divide the length by the number of rings to determine the annual growth rate of the tree.
  5. Divide the radius (cm) by the annual growth rate to calculate the age of the tree

Several trees were cored on Ampersand Mountain using this technique.
Reportedly there is a Yellow Birch (Betula alleghaniensis) on Ampersand Mountain with an estimated age of 600 years.

Ampersand Mountain Trees - DBH approx. 80cm
Species Length of Core Sample (cm)Number of RingsAnnual Growth Rate (cm/year)Estimated Age
Acer5.3170.311128
Acer13.31030.129310
Tsuga11.91190.10400
Tsuga14.6810.18222
Betula9.5900.106377
Betula7.6520.15267


Larch trees were cored at Ferd's Bog in order to estimate their age.

Ferd's Bog Larches
Species DBH (cm) Length of Core Sample (cm)Number of RingsAnnual Growth Rate (cm/year)Estimated Age
Larix8.964.5540.8354.00
Larix8.284.14600.6960.00

Questions for Exploration

  1. How does the DBH of the trees in the deciduous forest compare to the DBH of the trees found in the bog?
  2. How does the annual growth rate of these trees compare?
  3. At 60 years old the Ferd's Bog Larches have a DBH of approx. 8.5cm. What was the approximate DBH of the trees on Ampersand Mtn. at 60 years old?
  4. Will the trees found in Ferd's Bog ever reach a DBH comparable to those found on Ampersand Mountain? Can you explain your reasoning?
  5. Pictured here are some of Larches found on the mat at Ferd's Bog. Can you explain why young Larches are healthy whereas the older larches are very unhealthy?

    6. Larches at Ferd's Bog

Interested in seeing more of Ferd's Bog?

Goodnow Mountain Diversity Study

These data were recorded at the base of Goodnow Mountain, approximate elevation 1700 ft.
Climax vegetation was primarily deciduous containing several species of ferns and herbaceous shrubs.

Goodnow Mountain Diversity
TS N H E
Canopy 4 43 1.87 93.5
Floor 16 574 3.12 78.1

Questions for Exploration

  1. Compare the statistics of the Goodnow Mountain diversity study with the diversity studies of the forest and field transects at Camp Huntington.

Websites and Equipment

National Climatic Data Center
Click here to obtain climate information from anywhere in the world.

University of Arizona
This website offers dendrochronology information for educators.

Henri D. Grissino-Mayer's Science of Dendrochronology.
This page can be used directly with students. The page contains images of trees and tree rings, interactive question / answer, and links to several other sites.

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