NEW STORIES FROM THE SOUTH: The Year's Best, 1990, edited by Shannon Ravenel (Algonquin Books of Chapel Hill: $9.95; 229 pp . ). The odd thing about short-fiction anthologies that label themselves as being "from the South" (never the "Midwest," or the "Northeast") is that, despite what seems like an affectation, the stories, sure enough, do sound Southern. Why? Editor Shannon Ravenel admits to confusion, herself: "a strong narrative voice . . . deep involvement in place . . . in family bonds and in local tradition." Whatever. Happily, all but one or two of the 16 stories making up this collection succeed resoundingly in not only sounding Southern but in casting light--much of it harsh light--on characters, or circumstances, of great intricacy. Ravenel has picked wisely and sensitively in this well-rounded study of people in crisis or at crossroads.