First and foremost... FANTASTIC WORK! There is not much to say about this piece. As a digital painting it looks great. As a piece of fantasy art, it looks great.
As for the ratings:
Vision: Perfect, I think you accomplished what you wanted. A living tree.
Originality: Not bad. The piece looks wonderful, but I have seen this image in one way or another several times. But who cares! We all love to recreate things we see. It's what artist do.
Technique: It's solid. Your structure and build of the piece is spot on perfect. Digital paintings get away with many flaws because it looks cool. My art teachers might rip you a new one but at the same time praise you for letting certain details go to concentrate on others.
Impact: Eye catching! From first glance I wanted to look more at the piece and find out about the artist. This makes other artists want to try it or just draw something. Inspiring.
Overall, 5 star performance.