Here's a photo that shows the difference , the 2x6 on top is current SPF :'( :( , the 2x10 on the bottom is 1960's vintage :) .
(https://i21.photobucket.com/albums/b299/PEG688/Aug17.jpg%20)
No wonder span charts have been changed :o ::)
No wonder people are using more metal studs and joists.
And I always joke that lumber is so green these days that we buy it by the gallon.
That's pretty impressive
Of course, back in the days of Big Rail, and before treated wood, my county was pretty well deforested for railroad ties. Might have grown back by the 60's, only to be cut again.
Rumor around here is that pines can't successfully be planted/harvested more than once withoug a long fallow period. Makes sense to me.
The difference in the diameters of the two trees show you the way we are headed.
Already, in much of northern Europe the engineered stud has replaced the solid wood stud. Much like a TJI or I-joist it has a fiber web with nailers or flanges on either end - about a 2x2 (which can be cut from pretty small trees). They are the equal of a 2x8 so there is more room for insulation. Ultimately it will be the same here.