The sample, which is at this point a long, skinny, cylindrical sample, is transported to the laboratory for preparation.
Our analyses demonstrate that winter temperature prior to the season of growth, current year April precipitation and April–May drought (sc PDSI) exhibit direct relationship with the ring–width chronology when correlated with monthly or seasonal climate data.
Thirdly, this factor must vary in “intensity” over time and result in correlative variances in the width of the rings within the tree.
And, finally, these environmental factors must hold true over a large enough area to make extensive coring and study a worthwhile endeavor.
First, the type of tree from which one is considering taking a sample “…must add only one ring per growing season.” Tree species that are generally useful for tree-ring dating include Douglas-fir, white fir, ponderosa pine, post oak, red oak and sugar maple (Martinez 1996).
Second, though obviously a wide range of things affect the growth of trees, there must be one such factor that dominates the limiting of growth in the given area.