Dendrochronology (The science of reading and dating tree rings)

Dendrochronology (den·dro·chro·nol·o·gy) is a new word for me. It means the science of tree rings to understand the detailed history of a single tree or entire forest system. Known as tree-ring dating, the scientific method of dating timber, archaeological artifacts, and environmental changes by analyzing annual growth rings in trees.

How to Read a Tree

Suppression Era

After 1921, this tree no longer shows signs of fire. That shift coincides with U.S. forestry policies that called for aggressively fighting wildfires, which often caused forests to become overgrown. Extremely narrow rings in the tree’s last 50 years show its growth slowed due to overcrowding and competition for sunlight and nutrients.

Pattern of Fire

Between 1839 and 1921 this tree was scarred by fire, on average, once every 12 years. By comparing these burns to other scars from its home forest, scientists have determined that these trees routinely experienced every four years—often between November and March.

First Fire

The tree was more than 15 years old, the first fire left it to scar and damage its bark.

Seedling

The wide wide rings of the seedling tree for the first years indicate healthy growth. Created by fire or other disturbance, young pines in an open forest typically grow fast from the start to out compete other trees for sunlight.

Seasonal Growth

Each tree ring has two main colors. The light wood is from a period of faster growth during the wetter spring months. Dark wood is created later in the season, when the tree is growing more slowly.

Living with Fire

Trees often have these large open “catface”* burn marks on the uphill-facing side of their trunks. Wildfire flames, moving from low ground to high ground, will wrap around the trunk and create an eddy of more-intense heat on the uphill side of the tree.

*Catface is a partially healed scar on a tree or log.

In conclusion, they recommend a low-severity fire to be healthy habitat. To keep the forests healthy, they should be control-burned every five to seven years to improve biodiversity.  (Nature Conservancy History in the Rings)