Sam realizes he needs plenty of wood as well as food before winter comes.
Since Sam has decided to live alone in the wilderness, he needs to ready his home for the winter. He hunts many different kinds of meat, and finds a dead deer that a poacher killed to make warm clothing and a door for his tree.
During the summer and fall I had thought about the coming of winter. However, on the third day of December when the sky blackened, the temperature dropped, and the first flakes swirled around me I must admit that I wanted to run back to New York. (ch 1, p. 7)
Sam needs a variety of things to survive winter. He needs a good house that keeps the snow out. He realizes he needs dry wood to build fires. He needs smoked fish and dried meat that he can eat when there is no way to hunt food. Somehow, Sam is able to do all right.
The wood is important because in the winter it is hard to get dry wood, which is needed to start a fire. The fire not only keeps Sam warm, but cooks his food.