Wonderful work. I have to agree to a certain degree, if you look closely at the foreground and the way the (few species) of tree sit on mainly bare rock, I would indeed fill some bare rock with more shrub, or some fallen dead trees, and probably mingle more species between the trees.
Some rock in the world is pretty plain in color, but here some variation would give it more perfection. Perhaps some very dark, almost black patches, and/or some deep green like mosses. Easily accomplished with a few PF's, perhaps some stretched over X and Z like strata (probably best taken through a transform shader set to world).
