Hiding specific areas of unity2d layers.

I'm developing a parallax background system for my project and am having trouble with the transitions.

I want to add in a border (like a tree or rock in the foreground) to hide the seam and have only one layer render on one side of the tree and a different layer on the other side.

One solution I've been playing with is to have different cameras with layers masks. Not sure how to implement this effectively.

is there any way to prevent the camera from rendering specific layers, in specific areas of the screen?