Chronology expressed with tree rings

One of the most read chronologies using tree rings occurs in Aldo Leopold’s book, “A Sand County Almanac,” published and first printed in 1949 by Oxford University Press. Using a cross-cut saw, he dropped a dead oak that he used for heat. He determined the tree had 80 annual rings, the first being laid down in 1865. He used the date the oak died along with the number of rings in the wood to count back to the trunk’s pith region and first ring. Those rings in the wood – xylem tissue – are laid down by a meristem – growth-producer – positioned between a tree’s wood and bark.