In the Northwest, all of the moss that we have clinging to the lower part of our stumps, tends to pick up a ton of sediment, whether through wind dispersal or agent dispersal, (tons of squirrels flying up and down the trees) I don't know. At any rate, for the arborist, I can tell you... man, our low-cuts tend to really suck for the chain. For the timber-cutters: the Humboldt diagonals--which they are almost universally required to do--suck for them, since it requires them to snipe the opening, dang near right out of the duff. I can tell you: if you happen to nick a tiny bit of moss-caught sediment on the snipe of a really woodsy (tight ringed) Doug Fir, you'll have hell to pay just to finish the diagonal. I cut a tiny little (light suppressed) Fir today whose rings were so tight, that the late-wood diameter of the rings actually exceeded the thickness of the early-wood. Man, that pig was what a timber-cutter would call, "rock-hard".