I worked one summer for the BLM in Medford, OR. I remember one job where we marked all the "small" wood. It was everything under 36". We left some 60", 10 log trees, but I can't remember the species.
I also remember seeing some 1 log loads coming into town.
The biggest red oak I've marked was 54". On that job we left 30" trees, primarily for aesthetics and stocking.