I've read to surround your precious trees with peastone 1-2 ft out from the trunk, and use hardware cloth (a tight wire mesh) around your trees. leave
enough hardware cloth for years of growth, until the bark is at the stage where it starts to scab off and is no longer smooth. Bury the hardware cloth a few inches in the ground, and make sure it is wide (tall) enough to be well above the anticipated snowline. Good luck!