Which defect occurs due to fungal decay and appears as discoloration in wood?

Dave Bair wrote:

Okay, but Butt Rot seems like the most descriptive term.

Perhaps if describing my personal defects, but the question is about wood.

Added later 7 d 20 h 22 min 30 s:

I got this question from a timber website with quizzes to certify rating lumber, and it specifically said it was a fungal defect that affects structural integrity, and hence devalues the timber. IOW, both are different "defects" but spalting is often desired and foxiness is always a negative defect that is never desired. Following is an AI response to the question, which differs from what I had read.

Wood spalting and foxiness are two distinct phenomena that affect wood, but they have different causes and characteristics:

Wood Spalting
Spalting is a form of wood coloration caused by fungi colonizing the wood[1][3]. It occurs when certain fungi begin to break down the cellulose and hemicellulose in the wood, resulting in unique markings and patterns[2]. Key features of spalting include:

• Dark lines, zones, and streaks ranging from light tan to dark brown[2]

• Can occur in various wood species, with maple being particularly popular[3]

• Requires specific conditions like moisture content above 20% and temperatures between 50-104°F[1]

• Is a form of decay that can affect the wood's structural integrity if left unchecked[4]

Foxiness
Foxiness, on the other hand, is not mentioned in the provided search results. However, based on general knowledge:

• Foxiness refers to a reddish-brown discoloration that can occur in some woods, particularly maple

• It is not caused by fungi, but rather by oxidation of the wood's natural compounds

• Does not typically affect the structural integrity of the wood

• Is considered a natural characteristic of the wood rather than a form of decay

While spalting is highly sought after for its unique patterns and visual appeal, foxiness is generally considered less desirable in woodworking as it can affect the wood's appearance without adding the intricate patterns associated with spalting.

Citations:
[1] https://extension.psu.edu/what-is-spalted-wood
[2] https://customcountrywoods.com/spalted-maple/
[3] https://berkshireproducts.com/articles/what-is-spalted-wood-and-what-makes-it-so-special/
[4] https://www.wlwest.co.uk/news/spalted-wood-beautiful-but-is-it-safe
[5] http://www.hobbithouseinc.com/personal/woodpics/_spalted.htm
[6] https://www.woodworkweb.com/woodworking-videos-1/lumber-wood-videos/864-finding-spalted-wood.html
[7] https://upload.wikimedia.org/wikipedia/commons/1/1b/Gestocktes_Holz.png?sa=X&ved=2ahUKEwit-f77t7uKAxXkKkQIHfd-InoQ_B16BAgJEAI