I actually got the idea for the trees from one of my favourite games, Duck Duck On The Loose https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.lexaloffle.com/...
Essentially, layer a stack of circles (of varying colours) offset with a Z value. Shift each circle in the direction from the camera to the screen space position of each circle, using the Z value as the mmagnitude of the vector.