These first new cells are large, but as the summer progresses their size decreases until, in the fall, growth stops and cells die, with no new growth appearing until the next spring.The contrast between these smaller old cells and next year's larger new cells is enough to establish a ring, thus making counting possible.
When applying this principle to dendrochronology, it says that the variations in conditions present today must have been present in the past.
This does not mean to say that the conditions are exactly the same but that similar kinds of influences affected the similar kinds of processes.
Checked through a variety of methods independent of tree-ring growth, this principle has proved to be valid.
Review all the principles of dendrochronology as complied by Chronology Building The climatic changes or patterns in specific geographic areas can be traced by the study of old living trees.
Samples taken from trees of unknown age can then be studied for matches with samples from trees with known sequences of growth.