Help understanding the physics of modelling

[Midgardsormr]

ManOfSteel's right on the nose with the reason for the x-shaped tree. These scenes are meant to be viewed as though you're standing in them, not from straight above. If you're changing the perspective that drastically, you could absolutely replace all of those cards with different cards meant to be viewed from above. Or… hmm… a better approach might be to add a disc to the top of each one that's set up so as not to cast shadows. That way, you get the shadows from the original trees (a two-plane conifer will still cast a surprisingly reasonable shadow, even though most of it is empty air), but what you see is the new card, which completely, or nearly completely, obscures the X-trees. You might also be able to make the discs single-sided, so they only render if the camera is above them. That way, you preserve the original landscape if you move the camera back down to eye level. I know exactly how I'd do it in Maya, but I don't know what the best approach for Blender or Sketchup would be.