Brown void is just fine in my opinion! It's just that it's kind of an milky-grey-kind of brown that you're using, which at the same time takes visual priority (since it's quite bright and as well a large field) and creates confusion between the front and back layer since they are both rich in desaturated colours.
The solution I propose is simply making it a bit darker, to up contrast in the front layer and at the same time take away attention from the void area.
Also, i'd like to see some definition in the tree crowns, the clutter that's there right now just reminds me of big blobs of papier maché. Doesn't feel too natural and/or lush
