Tundra, the coldest of all Earth's biomes, is composed of numerous living and nonliving elements. Two different types of tundra exist on Earth. Arctic tundra encompasses the large swath of cold treeless plains encircling the North Pole. Alpine tundra exists on high mountain tops where trees cannot grow. Both types of tundra are shaped by their component abiotic and biotic factors.
Biotic and abiotic factors include the living and nonliving elements of an ecosystem or biome that help shape that system. Living organisms, such as plants, animals, fungi and bacteria, compose the biotic factors. Abiotic factors on the tundra include the nonliving elements of the ecosystem, such as temperature and precipitation.
Abiotic factors characteristic of the tundra include low temperatures and high winds. Low precipitation and permafrost also help shape the arctic tundra. Winter temperatures on the arctic tundra average minus 30 degrees Fahrenheit. Alpine tundra temperatures range more widely, but are often below freezing. Harsh winds frequently blow on both types of tundra. The arctic tundra receives precipitation of only 6 to 10 inches per year. Soils are generally poor and low in nutrients. The low rate of decomposition of organic matter means soils are formed slowly. In the arctic, only the top layer of soil thaws in the summer, leaving a frozen sublayer called permafrost year round. The permafrost traps moisture on the soil and results in important bogs and ponds. Water drains more effectively in the alpine tundra than in the arctic tundra.
The species able to survive given the combined abiotic factors of the tundra compose the biotic factors. The harsh conditions prevent trees from growing on either arctic or alpine tundra. Plant types adapted to conditions on the tundra include low shrubs, sedges and grasses as well as reindeer moss and a variety of lichens. Few animal species live year-round on the tundra. Species such as caribou, reindeer, arctic hare, ptarmigan, lemmings and musk oxen are the primary consumers on the arctic tundra, while arctic fox, snowy owls, polar bears and wolves are the primary predators. During the summers, when wetlands abound on the arctic tundra, mosquitoes and flies provide important food for the many migratory birds. Some common alpine tundra animals are small ground mammals such as pikas and marmots and larger animals, including elk and mountain goats.
Biomes and their component ecosystems contain numerous interconnected factors. The biotic and abiotic factors work together to shape the tundra and keep the ecosystem functioning. When one factor in an ecosystem or biome changes, its impacts cascade through the system. For example, if arctic tundra temperatures rose significantly, the permafrost layer would disappear, which would change the entire system.