in the tundra of the park, layers of topsoil collect on rotten fragmented rock moved by thousands of years of glacial activity. mosses, ferns, grasses, and fungi grow on the topsoil. in areas of muskeg, tussocks form and may collect algae. the term 'muskeg' includes spongy waterlogged tussocks as well as deep pools of water covered by solid-looking moss. wild blueberries and soap berries thrive in the tundra and provide the bears of denali with the main part of their diet.