Subject: Why can pine trees stay green all year long, and leafy trees can not?

I told my grandfather that I had once learned that the reason for the 
existence of pine trees is that they can survive in places where it 
SNOWS.  I said that deciduous trees would keep their leaves all year 
long if they could, but that the reason they can not is that when it 
snows, the broad leaves hold a lot of snow, and their limbs would 
break off. So, they shed their leaves before it is likely to snow. 
Pine trees, on the other hand, have needles that shed most of the 
snow, thereby allowing them to remain green, and perform 
photosynthesis, all year long.  I said that in places where it never 
snows, trees can have broad leaves without shedding them in the colder 
season.  I said that logically, there should be no pine trees in 
places where it dosen't snow.  He doubts that snow is the main or only 
reason for the existence of pine trees.  Am I right, or did I make 
this up?

Re: Why can pine trees stay green all year long, and leafy trees can not?