Tundra is the coldest of the world’s biomes.Tundra is a cold, treeless, plain-like area with a frozen subsurface.Some characteristics of tundra are an extremely cold climate, low biotic diversity, and limited drainage.Tundra has a simple vegetation structure and a short season of growth and reproduction.Much of its energy and nutrients are in the form of dead organic materials.

There are two major categories of tundra, artic tundra and alpine tundra.Alpine tundra is located at high altitude on mountains around the world.Trees cannot grow in these regions.The growing season in the alpine tundra is approximately 180 days and the temperature is usually well below freezing after dark.The main differences between alpine and arctic tundra are their locations and drainage.While the arctic tundra experiences very limited drainage, the alpine tundra is well drained.

Arctic tundra is located in the northern hemisphere, in the area encircling the North Pole and extending slightly south.The growing season in the artic tundra ranges between fifty and sixty days per year.This growing season occurs during the summer, when temperatures average between 37-54° F.Although there are approximately 1,700 kinds of plants in the arctic and sub arctic, there are no deep root systems.This is due to he layer of permanently frozen subsoil, permafrost.The permafrost is consists mostly of gravel and finer material.

There are a few variations in the types of tundra, including wet tundra, dry tundra, and scrub habitats.Wet tundra is mostly found in areas of arctic tundra throughout the sub-Arctic.Wet tundra is characterized by permafrost below the surface, few if any trees, and a variety of lichens, mosses, heath plants, and an assortment of wildflowers growing on dry tussocks.Dry tundra is most often in alpine tundra regions, mountaintops or high hills with well-drained soil.Arctic scrub is a portion of the Arctic tundra in river drainage area and sheltered valleys where willows, birches, alders, and poplars are able to grow successfully.The arctic scrub is where a variety of birds make their nests, because this area provides some shelter from the high winds that are typical of the tundra region.

 Informational Sources:

           http://www.ucmp.berkeley.edu/glossar/gloss5/biome/tundra.html

        http://www.enature.com/habitats/show_sublifezone.asp?sublifezoneID=54