The Ouroboros and The Tree of Life is a popular symbol and the interpretation I appreciate is one that I first heard the Pageau Brothers discuss. It goes something like this.
Time is associated with the snake, in particular, the snake eating its tail or ouroboros, because time is an ever-renewing cycle. The Tree stretches down into Earth, into matter, into space (the three dimensional world), and rises up towards Heaven, into time, spirit, the sky. The tree symbolizes the bridge between these opposing forces, with its roots firmly planted in the earth and its branches reaching towards the heavens.
Before the fall of man, humans were the mediators between heaven and earth, maintaining the balance between the two realms. However, the fall disrupted this equilibrium, causing the wheel of time, which is associated with life, to become unhitched from the spatial axis and turn destructive, leading to death.
It was only through the sacrifice of Christ on the cross (a tree) that the balance was restored, and the tree of life once again became the connection between heaven and earth, matter and spirit. Through the resurrection of Christ, the cycle of life and death was restored, and the wheel of time was once again aligned with the spatial axis, allowing for the continuation of life.
