What happens when a fire just burns the understory and doesn't kill all the trees?

Cycles of fire return to lodgepole stands on a regular basis, but each fire can leave the stand in a different configuration. Compare the two burned areas above.

"The veterans [fire survivors] most commonly occupy unusually wet spots, in which surface fuel was too sparse to support a hot surface fire, and crownfire did not occur for some reason." From George Fahnestock, [ca. 1973]. Fire, Fuels and Flora in Wilderness Management: The Pasayten Case.