Re: Why do pin oaks keep their leaves in the fall when most other trees don't?

I an not sure of the exact species of oak in the question.  However, it must 
be either a hardy oak or a non-deciduous oak which would keep its leaves 
when other oaks and trees drop leaves.  This preparation for winter or a 
dormant period involves reabsorbing all the useful materials from the leaf, 
hence the brilliant fall colors, back into the root and stem of the tree.  
This applies for those that lose leaves for winter.  If the pin oak keeps 
it leaves the only real thing to be said is that the plant has evolved to 
that end.  This would have required the tree to allocate resources 
differently from those that lose leaves and become dormant.  It would also 
help if the leaf would not freeze and would be able to warm to a point at 
which photosynthesis could occur.  

Why questions are the hardest to answer especially when talking about the 
plant and animal world.  I hope this information helps.