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Growth and Sensitivity

The amount of rainfall that an area receives can certainly affect the width of tree rings, but so can other factors. Factors such as temperature, soil conditions, and the gradient of the slope can have an effect, as can wind, snow accumulation, and how much sunlight a tree receives.

Complacent

Sensitive

Still, the amount of variation in a tree's rings can vary between species of trees and between trees of the same species.

A tree whose rings vary in width are called sensitive. These trees can have a wide ring if conditions are conducive to growing and a narrow ring if they aren't.

Sometimes, a tree's annual rings don't show much variation. The reason can be simply that it's a species that isn't prone to variation. Or it can be that it's located in a part of the world where the environment doesn't vary greatly from season to season. Or it can be that it's growing where the water table is high enough for it to get all of the water it needs. Trees whose rings don't show much variation in width are called complacent.

Tree-ring scientists prefer to work with tree-ring samples from sensitive trees, as the variation in their annual rings allows for crossdating.

Anatomy of a Tree Ring
Growth and Sensitivity
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