Wikipedia
The term sawlog refers to that part of a tree stem that will be processed at a sawmill. This is in contrast to those other parts of the stem that are designated pulpwood. The differences are that sawlogs will be greater in diameter, straighter and have a lower knot frequency.
Sawlogs most often come from the "butt end" of the stem and are the most financially valuable part of the tree.
Usage examples of "sawlog".
Enthusiasts discovering individual trees which have made prodigious growth, or even fairly extensive stands on fertile soil with heavy rainfall, will compute sawlog yields at 40 or 50 years which are much too optimistic for general application.
He rolled up the window to avoid the dust storm that arrived along with the deafening blast of an air horn as the tractor-trailer loaded with sawlogs went speeding by.