Comment by mapt
I've read this, but I'm not 100% clear on this. I think it's probably entangled with the glaciation / interglacial transition, which happened relatively recently. Earthworms are invasive in Michigan, but so are _trees_ in that timescale. It seems like having a foot thickness of forest duff decomposing slowly is probably not a very ecologically stable situation, and might be a temporary phase as the forests creep northwards and the temperatures creep up. Earthworms are not especially frost-hardy, and need to burrow deep enough to survive frost, which is physically difficult as you go farther north.
Has a drastic change occurred in the forest floors of, say, temperate Georgia?
I guess I don't care to understand your point.
The earthworms I am talking about were introduced by modern fishermen and have reduced mushroom habitat.