Why would old growth and second growth be any different? An old growth tree was a new tree once. Is it that a younger tree will have wider growth rings? Is it that old growth trees that we have experienced were under more stressed conditions during their lives and therefore have narrower growth rings than today, assuming that today and in the near future we predict that we will not have such stressed conditions?

I can understand why fewer growth rings would be advantageous, much like Osage was split by the Indians to have a single growth ring, thus flexible and strong. I just don't exactly understand why a newer tree would be different than an older one as far as the width of its growth rings. A tree doesn't know it's a second does it? Or maybe it has something to do with an old growth tree, grows among other old trees, and has to fight for light, and grows slower due to less direct sunlight. When old trees are clears(usually by us), more light= more growth in a given year. Maybe through deduction I just answered my question?