I checked, and it appears that some generals have a "Understanding of logistics" trait. But it seems to me that the entire "supply situation" traits do not work in reasonable fashion: in a multi-turn siege or while marching through a large province your general will almost certainly gain the "Starving" trait, regardless of what time of the year it is, the fertility of the region in question, the proximity to own territory or a coast where your faction has naval superiority. I am guessing the trait cannot check for such factors, but as it stands it does not work in a fashion that seem reasonable to me, and in any case the -3 morale effect is a poor substitute for proper starvation, desertion and mutiny.