Soil types common to the tundra include permafrost and polygon soils. Permafrost refers to soil that is permanently frozen 1 to 2 meters below the surface. Polygon soils are cracked, patterned soils created from surface shrinkage due to frozen winter temperatures.
The permafrost soil insulates lower soil layers from biological activity, making it difficult for plant roots to reach deep soil layers. Materials can become trapped in layers of permafrost for eons. Water is limited, except during the occasional thaw.
The polygon soil type contracts during the winter, creating polygon surface shapes surrounded by large cracks in the ground. In the warmer summer months, these cracks fill in with melt water and can form unique plant and animal communities.