I've never been hit by a tree because it generally falls away from you and I start walking backwards as soon as it starts to topple. If you can't dodge a tree, good luck with a Troll. :)

For people like monsterfurby (and myself) who like the trees, the "Tree Respawn" mod https://www.nexusmods.com/valheim/mods/37 will plant a sapling if you clear the tree stump away. This will obviously only apply to trees that can currently be planted because they have a seed/sapling in the game.