Trees: We discussed it amongst ourselves. We discussed it at The Warp's discussion board. And we decided, by consensus, that models in trees suffer -1 RC for every 2" they are placed within the tree line. Likewise, enemies shooting at models within trees suffer -1 RC for every 2" the targets are within the tree line, up to a maximum of -2 RC.

Cows: I have scenery made of toy cows. Yeah, its kind of corny, but it really captures the "midwest agriculture" look I want in my scenery. So cows are soft cover to any model on the cow scenic base, and cows also cause RC: -1 to any model shooting at targets beyond the cows. So if you have cow scenery, there's how to use it.