What was stored in certain sections?
As he learns how to survive, basically by trial and error, Brian Robeson learns what items will be valuable to him in the long run, and those which will not. The first item he gathers and "stores" is wood. He knows he needs a shelter, and learns after his first shelter leaks, that he needs to reinforce it. Once he discovers a method to start a fire, wood and kindling are something he notably always has on hand. He also thinks to gather a pile on a bluff for which to make a signal fire.
Because berries seem plentiful (and are certainly better when ripe) Brian does not necessarily gather and store these for later. He does, however, refrain from eating all of the turtle eggs he finds, and stores some in a hole. When all of his buried eggs are one night stolen by a skunk, Brian realizes he needs a plan for longer food provision. He figures out a way to lure, trap, and essentially store live fish.