And of course:

There is a tree in Paradise
And the pilgrims call it the Tree of Life
All my trials, Lord, soon be over

The 'tree of life' seems to be a very common theme in most religions, as 'The Golden Bough' has found. My guess, based on little or no evidence, is that it is something to do with the way a mature tree is clearly alive but is virtually unchanging in a human lifetime. Off the top of my head here are a couple of songs what have that sort of theme

Sair Fyled Hinny (DT: AULD MAN TAE THE OAK TREE)
What's the Life of a Man any more than the Leaves?
And for a non-traditional one: The Green Green Grass of Home!

To that theme you could add a 'Tree of Death' motif: the Gallows Tree, neatly linking Odin hanging on Yggdrasil with the life of the Aesir.