John, nice looking bowl, I like the flair of the rim to the edge. Why does some box elder not have much red? Is it mostly sapwood? Or do some trees just not have as much red in the wood? Maybe soil related? Just wondering.
The red coloration is a result of what dendrologists call "a non-specific host response"
to wounds in the tree. Extreme stress can also cause it such as wind shake. In most cases though (nearly all) the wounds are the result of borer infestation i.e. the Boxelder Bug (they make shallow wounds to suck sap but only in the female trees) and the Ambrosia Beetle are the most common. Where the red pigment is found, mycologists have discovered two fungi which are most prevalent but not always, which eliminates the possibility of the etiology being due solely to fungi.
Many sites on the internet repeat the once-held belief that the red color is a result of one or more fungi i.e. Fusarium reticulatum
or Fusarium solani
(which are the two most prevalent when a fungus is
present). The actual cause of the red color has not been isolated past the known necessity of a borer attack or extreme stress, which precipitates the non-specific host response. It's like the tree's immune system's response.
There have been serious efforts to both understand the cellular nature of the phenomenon, and also commercial efforts to replicate it, but scientist have not even been able to discover the chemical composition of the red pigmentation in the laboratory. Not even generally. They suspect it is a phenol but are not even sure about that. So as far as what causes it to occur in the tree, all that is known for certain is that without some type of wounding or extreme stress, the tree will not initiate that mysterious chain of events necessary to cause the red color to appear.
My theory is that God is smarter than us.