Dan,
 
During my first field experience, I excavated a root cellar at Locust Grove
in Louisville, Ky.  Amy Lambeck Young at the University of Tennessee, has made
the research conducted there the center of her doctorate work.  She has some
facinating information concerning the root cellar.  I do not much about the
feature, other than it was in front of the hearth of a slave cabin.  I do know,
it would be well worth your time to see her work.  Unfortunately, I do not have
her adress with me now.  However, you can contact her at the University of
Tennessee department of Anthropology and her address is probably in the SHA
directory newletter issue.