I'll wait with a critique on the texture and the leaves at the moment. I just wanted to touch upon your tree's anatomy and pose, as I feel there's still a few things that haven't been mentioned. Judging from the face, you *might* be going for a slight abstaction of the human figure because of him being a tree and all. Still, I tried doing your picture with a few tweaks to his structure:
I noticed that he's leaning over to the right on your version. I Don't know if this was intentional so I tried to correct his direction. Also added roots because I thought it looked a little strange with the tree just ending flat like that.
Hope it was of some use. Looking forward to your next edit.