What idea does Steinbeck convey with the simile, "The heat goes out of it like the living heat that leaves a corpse"?

We find this quote just after the Joads have left their land behind, the only land that they have ever identified with. Note the words "corpse" and "death", this is Steinbeck not so subtly foreshadowing what is to come. As the land dies so do the Joads begin dying. The two are reflections of each other. Indeed, not long after, Grandpa is the first casualty of this disconnection.