|White spalting, aka white rot|
The entire log was covered with these. The patches were slightly raised above the wood, and spongy to the touch. Although it was a dry day, the whole log felt damp. I couldn't find any of the mushrooms which commonly cause white rot, like turkey tail or other bracket fungi.
This is the work of a microscopic fungus or possibly a bacterium that eats the pigmented part (the lignin) of the cell walls of the wood. The lignin functions as part of the support structure of the wood; as the fungus removes it, the wood becomes soft. Since the lignin also works as waterproofing, this whitened wood is also more absorbent.
Brown rot destroys the cellulose in the cell wall, leaving the pigmented lignin behind, so the wood disintegrates into little chips, but stays dark. White rotted wood holds together longer.
|Brown rot in a stump. The wood is dry and flaky and crumbles in my hand.|