When an Archwood sapling grows into a tree, the blocks underneath it are replaced with dirt. The tree itself - the wood and leaf blocks - doesn't replace existing blocks or tile entities, but when it replaces the ground with dirt it does.

I noticed this because my Create-based Archwood tree farm kept breaking when the trees deleted the mechanical bearing at the center of it. I was able to work around it by just keeping the saplings at least one block away from the bearing.

I'm not totally sure this is a bug, but it certainly surprised me so I thought I should mention it.