During the winter, when the visible parts are dormant, the roots continue to function and grow even if the air above ground is brutally cold. This steady, persistent activity at root level fortifies the tree and prepares it for the rapid growth of spring. Winter root activity strengthens, giving trees staying power through the heat and drought of summer and fall.
I think we can draw two important parallels between us and the oaks. First, surface appearances aren't everything. Second, we each have a vital taproot.