Thanks for the answer, its kind of long way to just asign a new mat...
But while on subject.
I created a tree library with a (for my case) early test material, then on my scene I choose those created library tree. When i edit the source 3d files with the early test material , Q: How can i "update" the already library trees on a current scene?, i just asume that if they're referenced, forest "just" load the archives and reads the updated material. Or maybe I need to delete the trees from the geometry rollout and bring them back again?.