Re: How can I know the age of a tree, if I only have the diameter??

If I understand your message correctly, you also have a sample of the rings
of this type of tree.  If you investigate the rings, you can determine the
average ring thickness.  Then you can take the diameter of that tree and
divide by 2*(average ring thickness) to determine the approximate age.  

All measurements and samples should be taken at breast height to
standardize them. Apparently in Mexico, breast height is defined as 1.5 m
above the ground.

Please note that it really isn't very accurate to use the average ring
thickness of this tree to determine the age of another tree because trees
grow very differently even within the same stand, where they're all the
same age, species, and under the same conditions.

-Marcy LaViollette