How can you tell a tree's age (and past climate) from the rings in its trunk?
A dicot tree thickens each year as the vascular cambium adds a new layer of wood.
A dicot tree thickens each year as the vascular cambium adds a new layer of wood. In the wet growing season it makes wide, light 'spring wood'; in the lean season it makes narrow, dark 'autumn wood'. One light+dark pair is one year's growth, so counting the annual rings gives the age. Wide rings signal good, wet years and narrow rings poor ones, so the pattern also records past climate.
Key point
Each annual ring = one year of cambium growth; ring width records that year's conditions.
Common mistake
thinking a tree grows at a perfectly steady rate all year.
Memory tip
count light+dark ring pairs for age; wide ring = a good growing year.
Tap to watch or see it right here — the app stays open (it only opens a quick search if nothing embeddable is found).