On Fri, 31 Mar 2006 21:28:00 -0700, "James \"Cubby\" Culbertson"
Obviously it's both yes and no, depending.
Sap is resistant to freezing. Increasing the sugar content in sap makes
it more resistant to freezing, which is why you can't get maple syrup in
a place with mild winters.
Free water may indeed freeze. Freezing water expands, rupturing cell
membranes. So in the Fall period, some trees pump water outside the
cells by osmosis, leaving the cells themselves almost dry. If there is
any freezing, this happens _between_ the important parts, not inside
them, and there's simply some temporary distortion.
Some species have a thick corky bark layer that can freeze without
damaging anything important. Ice is a better insulator than water, so
the core of the tree stays unfrozen.
The tree may indeed freeze and die. Sometimes you even see branches that
have been split open by this.