Why do Trees Rot Starting at the Bottom Center Core

[GregManning]

Now if I could just know if I was looking “up” the stem or “down” the stem. Neither of the co-dominant stems appear to have died, or become non-conductive. I can only assume round 1 came from a higher point in the tree, and the inclusion line would have become longer and longer in consecutive rounds cut from above it.

Those 2 discs were cut side by side.
Disc 1 (larger diam.) was actually lower than 2.