Tundra
Tundra is the coldest biome, and short days in winter limit the growing season. Tundra occurs close to the North Pole, above 65° N. The South Pole is largely surrounded by the ice and seas of Antarctica, and so there is very little area with plants. Precipitation is low, but because rates of evaporation are also low and because drainage is commonly poor, the ground is usually waterlogged and permanent ice occurs below a few centimeters of soil. Primary producers are mostly mosses, lichens, herbs, and low shrubs. Grasses and sedges occur in drier places, as do other flowering plants. Plant diversity is low, and most plants are small. Caribou are conspicuous grazers, but other primary consumers, including rabbits, birds, and insects, occur as well. Wolves and foxes are key predators. Fungi and bacteria decompose organic detritus, but low temperatures and water-