The tundra ecosystem of Alaska is known as a “cold desert.” It receives very little precipitation, about four inches annually. However, it is rich in wetlands due to permafrost, which traps moisture close to the surface. The temperatures vary widely, also producing persistent winds. Although treeless, the Arctic tundra is an abundant ecosystem. Many organisms find their niche here including many migratory bird species and mammals such as caribou, foxes, bears, and small rodents. Which factor of the tundra ecosystem is biotic?