Is it possible to apply an Auto Landscape Material only to one specific layer of the Landscape?

Hello! My landscape consists of 3 Layers, one of them is used for the mountains which where created with help of a alpha brush. My normal layer has 4 Materials (Grass and roads materials). Now I want to apply an Auto Landscape Material so that the mountains look better but I want to apply it only on the mountains layer because for the rest I want to have flexibility and use my own already defined layers. Is this possible and how?