How do trees survive loss of leaves?

Some trees and shrubs shed their leaves in winter because the lower levels of sunlight would reduce their ability to photosynthesise. The tree enters a dormant phase until the light conditions enable it to resume photosynthesise in the spring. The old leaves are shed otherwise they could cause damage to the tree during the strong winds and snow fall which often occurs during the winter. A branch full of leaves acts like a sail in strong winds and can break or even cause the whole tree to blow over. A bare branch allows the wind to pass with less resistance and is less susceptible to damage. Likewise a bare branch will hold less snow, so it is less likely to crack under the weight.