I think Dave is referring to the tree arrangement or placement? This leads us parabolically back to another key factor : animation. When youre setting up trees, or placing ANY objects really, there's two ways to do it : animateable later or easier-to-start-a-scene-from-scratch-later. If you put them all in based off of only the "Main Render Shot" viewpoint alone, fine, if you just want to get the image done. But as out computers get faster, and animation of ridiculous scenes becomes more viable, it's cool to set up your scene so the trees are REALLY in the right positions, and not floating, and are far enough below the surface that the stupid roots aren't showing too much... Tedious work, at best! My silly Shadow's Wall scene was like that, I wanted everything TOO precise and it just took forever...