That sure is some beautiful work. It's taken me a while to go through all those pages too.
You're developed the leaves so much, colour-wise, placement and shape yet I feel the trunk is being neglected, I think I personally have issues with the roots themselves, there seems to be no evidence that the roots ever go into the ground.
If you think about it realistically, the roots would be (at least) half submerged into the ground, I'd love to see some above like you have (maybe with a bit more detail, to reflect the amount of detail in the leaves) but also bumps in the grass where the roots go under. I feel like the Tree really needs to be held in place, by some clever shading showing the roots are there, without being shown.
hope this helps in some way. Just something different to think about I guess.