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Challenges to Accurate Measurement of Tree Rings

Ring-porous and diffuse-porous

Diffuse-porous sugar maple core.

Ring-porous hickory core.

Radial growth of trees is due to the periodic formation of xylem cells by the cambium. Growth rings are distinguished by differences in cell diameter and cell wall thickness produced during the relatively fast early growth in the spring (earlywood) and the late growth in the summer (latewood)

Growth rings of ring-porous species (ashes, oaks, and hickories) are easily distinguished because of the concentration of large vessels in the early wood.  In addition, the latewood of ring-porous trees is typically darker than the earlywood further facilitating ring counting.  Diffuse-porous species (sugar maple) have smaller vessels that are more uniformly distributed throughout the growth ring. This makes the rings of diffuse-porous species more difficult to identify. 

Diffuse porous species present a much greater challenge to measurement. And it is therefore plausible to assume greater error in the readings of the sugar maple cores.

False rings

This red cedar core is also difficult to read accurately because it has many false rings. False rings can be mistaken for true rings and can be problematic when attempting to crossdate tree ring patterns. False rings are defined as bands of what appear to be latewood, followed by earlywood, followed by true latewood all within the boundaries of a true ring. They are caused by stresses during the growing season which are significant enough to induce changes in the size and shape of the rings. Fortunately, with proper training false rings can usually be identified.


Another challenge to accurate core readings was encountered while mounting and drying the cores. The bark on some samples fell away from the wood and without the bark-wood interface on the core it was difficult to identify the outermost ring. Inaccurate identification of the outer ring could cause the most recent years to be missed or tree rings could be measured backwards if the wrong end is identified as the outermost ring. Because of the potential for error, most cores which lost their outer bark were not included in these analyses.   

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Date Last Modified: 4/22/99
F&ES 519B, Spring 1999