Zoom in on the tree leaves, it's very visible on those. They appear as green rings, slightly lighter on the edge, giving it the appearance of a ring. You can also see it very clearly in the spots of sky between the leaves, they appear grey with an almost white outline.

A good video from a pro going through why someone might deliberately choose characteristics like this: https://www.youtube.com/watch?v=O0zH7J_Vmg4 (4:47)

Zoom in on the large tree in the background. It looks as if it has ornamental balls hanging off it.