Tundra Biome

The Tundra is the biome farther north than any other.

Biodiversity is low in the Tundra, especially to the northernmost portions of the biome.

For more than half of the year the temperatures are so low that ground is frozen solid. During July, when daytime high temperatures approach 60oF, only the upper few inches of the soil thaw. Soil below those depths remains permanently frozen and is called “permafrost”.

Plants’ roots cannot penetrate the permafrost. Consequently their roots are shallow which means they aren’t anchored well into the soil. Therefore, the plants grow low to the ground and trees grown as vines.

Winter temperatures fall to WAY below freezing. Normal winter lows may be -30oF to -40oF and – 60oF is not uncommon.

One of the few trees that grows in the Tundra, the Arctic Willow towers over other Tundra plants. It grows to one foot tall. Its shallow roots won’t let it grow taller. Its branches creep over the ground like a vine.

Many tundra plants have tiny leaves to limit transpiration in the dry air. Plants must grow, flower, and reproduce very rapidly because the growing season lasts only from early June through early August.

Another adaptation plants have to the short growing season is thermogenisis. These plants produce metabolic heat that enables them to grow up through the snow to extend the growing season.

Ten inches or less of precipitation falls annually. The Tundra would seemingly be a very dry place. However, during the summer the soil is soggy and boggy wetlands are everywhere.

Because the temperatures are low, as snow and ice melt on the soil’s surface, the air is too cold to cause it to evaporate. It simply forms puddles on top of the permafrost.

This aerial photograph shows that water is everywhere during summer. The upper few inches of the soil are saturated in many places. The wet soil supports the growth mosses, the Tundra’s dominant plants.

Carpets of lush green moss covers the wettest soils.

As the weather warms and snow melts, plants grow rapidly, then…..

they all the flowering plants burst into flower so they can reproduce before the cold returns a few weeks later.

This is a Musk Ox. It’s not a cow, but a large, arctic goat that inhabits the Tundra. Its long, thick fur and short stature keep it warm through the winter. It digs through snow and ice to find the remains of plants that sustain it through winter.

To avoid predation, the smaller mammals that remain active through the winter, rely on camouflage. The only place they have to hide is in the snow.

During summer, they shed their white fur and replace it with colors that will blend with rocks and plants.

Arctic Hare

Ermine – winter (above) and summer (below). The ermine is a weasel that eats lemmings and ptarmigans.

Ptarmigan winter and summer. They undergo a molt that replaces their white feathers with brown ones for summer.

Lemmings are rodents. The hibernate for 7 to 8 months per year. During the Tundra summer, they must eat as much food as they can to build enough fat to last them through winter. They hibernate in cavities in the permafrost that they line with grasses and moss. Lemmings experience “boom and bust” years. About every four years, they have sharp increases in population and their predators do very well. In years where Lemming populations decline, their predators’ populations also decline.

Snowy Owls are Tundra predators. These birds are large. Ptarmigans, Ermine, Snowshoe Hares, and Lemmings are among its targets. In years where Lemming populations are extremely low, Ermine populations also fall and Snowy Owls find it difficult to find enough food to sustain themselves. They migrate south. About once every ten years, one shows up as far south as southern Ohio.

Arctic Wolf

Arctic Fox

A couple more white predators of the Tundra.

Caribou migrate north during summer into the Tundra to feed on the bounty of fresh plants where Musk Oxen are their only competition. They don’t tolerate the winter so they migrate. Musk Oxen stay through the winter.