Foresttale is a tribe called the Soulja tribe and are very important to nature itself for their lives are based on the forest itself.

Sans: based on a maple tree and gards that specific tree if harmed he's harmed same with the others

Papyrus: spruce

Undyne: dark oak

Alphys: seder

Gaster: oak

Toriel: apple tree

Asgore: Pink dogwood

Frisk: cherry tree

Chara: a rotted tree

Flowy: golden chain tree

Asriel: weeping willow tree

Grillby: Red dogwood tree

The Soulja tribe are vegetarian and will not harm animals to eat that is why the harvest from the soil

Due to the deforestation of their home they have been getting sick and dieing the trees are linked to their souls

When their tree starts to rot they rot from the inside that will kill them slowly and painfully as their bodies and magic return to the earth for rebirth of a new tree.