I look for my darker darks, which happen to be in the tree trunks, and then I add few delicate branches. This establishes scale. If everything in the scene had the same chunky thickness it wouldn’t represent the variety of sizes that exist in real life. Once I add a few of these the smaller marks, scale is implied for the rest of the painting.
Transform the image
My ground plane isn’t supporting the depth in the image as much as I’d like. So I copy the image and transform it with the Perspective tool. I then add a few implied texture changes to break up all the green. Even though there are no blatant perspective cues here, like railroad tracks, every scene carries perspective cues and it’s the artist’s job to reinforce them.