When tundra vegetation remains free from fires and other disruptions, the long-lived sedges form large clumps that are often drier than the surrounding soil and eventually become colonized by lichens, mosses, willow shrubs, and alders. These invaders slowly crowd out their predecessors, changing the environment by shading the ground, which reduces soil temperature and makes it even more difficult for annuals to become established. But fire, if only occasional (it occurs once every three to four years somewhere in the Noatak River valley), reverses this course of succession just often enough to keep annuals in the game. Like fire-adapted pines, which bank seed for future generations in tightly closed and long-lasting cones, the resourceful arctic annuals invest their future in an underground seed bank. We now know that every square yard of tundra soil holds many hundreds of seeds of diverse species. Biding their time in this cold-storage depository, the seeds await some change to tip the balance of competition in their favor. And in this frozen Eden, there's nothing like a good fire to rouse them from dormancy and spark a summer bloom.