The tree of life has been found in every religion and new age  a good example is the tree of life in the Garden of Eden for the Christians. For the world and the most imprtant meaning of this tree it is symbolizing life itself some cultures know this tree by other names like : Cosmic tree, the World tree and the holy tree.
The top with the leaves presenting the connection with heaven and the roots presenting
our connection with the earth.
In the mean time the tree of life is presenting also the four elements.

Fire : the sun for giving the tree to live ( some say food ).

Water : Wich goes in the tree you can see this as drinking water like we do.

Earth : Presenting the roots and the bound with earth we have.

Air : Presenting the environment of the tree.

Actually this tree is presenting everything there is life/ death and sleep the circle of life as
some people like to call this. Like I said the leaves and the top of the tree presenting the heavens is also to let us see we all go to heaven once we had done our job here on earth and we go back.
We can only return to the tree of life once we have reached enlightenment, for now the tree is guarded by Cherubim angels ( you know those small Cupido angels ) and to go there is crossing a whole
universe and planes you name it.

Well a lot of theories or facts just the way you see it is out there about this tree. I think it is not for nothing the tree of life is in all religions and ancient beliefs, I think this tree is meant for all
of us not only to teach us the meaning of life but also  to learn how easy it can be
so be conscious of ourselves and that we all can make contact with the earth, universe and God.