How do trees that lose their leaves for a lot of months stay alive??

Answer 1

They store energy in their sap in the root system.

Answer 2

As a tree's leaves are beginning to fall in Autumn nutrients are being moved into the main trunk and roots of the tree. When all of the leaves fall off, the tree is more or less dormant. That means that its rate of respiration is very slow. Kind of like how a bear goes dormant during the winter and sleeps all winter. The bear has a lot of stored energy that will keep it alive, but it doesn't need as much because it's breathing slowly. Just like the dormant bear, trees will breathe very slowly and not require as much stored energy.

Answer 3

That is the way nature designed them. It would take more energy to stay in full leaf, in the cold and darker conditions. Have you noticed that the leaves change colour before they fall? This is because the tree is taking all the sugar produced in the leaves and storing it deeper in the tree, so it can use it all winter long. When the leaves are deplete, they dry and fall off, no longer needed.