I think this checklist of PIE roots came from Gamkrelidze/Ivanov book:
Besides that the vocabulary may reflect ecological environment:
*Hegr- (a mountain),
*kel- (a hill),
*hap- (a river),
*perk-u- (an oak), *bhergh- (a birch), *bhaHgo- (a beech), *ei- (a
yew-tree), *(s)grobho- (a hornbeam), *hrtko- (a bear), *ulko-/*ulp- (a
wolf), *ulopek- (a fox, a jackal), *leu- (a lion), *leuk- (a lynx),
*el(e)n-/ *elk- (a deer, an elk), *ger- (a crane), *ghans- (a goose, a
swan), *karkar- (a crab) etc.
What are the IE developments for (s)grobho- ?
Hegr- ... mountain?