Thanks for the comments. I immediately saw a painterly effect too, but didn't mention that because I was curious if that was just my perception. Sometimes it's hard to tell because I have the entire context in my head.
I certainly do: the scale isn't immediately obvious, which is pleasingly disconcerting. Have you tried it in b&w?
Here's the whole stump I shot on my way in for some context.
The root is in the bottom center of this photo. The water level decreased a few inches while I was hiking and it started to dry out by the time I walked out. I actually wasn't going back to the tree for a photo; I went back to see how much the water had receded, and that's when the root caught my eye.
I did try it in b&w. Here it is. I felt it lost something, but I didn't spend much time on the conversion, so it might have potential.