The tree of life is merely an abstract
representation of the standing Goddess, the Creatrix with
upraised arms holding up the skies.
This assumes, of course, that there was a "Goddess" and not a bunch of goddesses. I just don't buy Gimbutasism; she (and those who follow along or even led the way) simply ignores too much, is too selective in her evidence, and overreaches it. As two particularly bad example, she decides early on that her Goddess is connected with birds and eyes. She therefore identifies any image of a bird or eyes as an image of the Goddess. She then makes the further step of identifying any sort of wavy or dancetty line as a bird, and therefore as a symbol of the Goddess. Pretty soon she is seeing Goddesses everywhere. It reminds me of the line by Maslow: "When the only tool you have is a hammer, everything starts to look like a nail" (which should be a warning to those (and I include myself) who see the three functions everywhere).
The idea of the cosmic pillar as tree equalling the doubtfully existing Goddess flies in the face of the identifying of such trees in general with what would be considered "masculine" trees, such as oaks and ashes. (I believe that the Baltic axis mundi was the feminine birch, but that is an exception.) Throw in the phallic nature of trees and I think that the identification of the two goes beyond believability.