Taiga

The taiga is the largest land biome on Earth.

Many people also call this region the boreal forest. It is a massive expanse of coniferous forests. Coniferous means the trees produce cones and have needles instead of broad leaves. You will mostly find pines, spruces, and larches here. This biome covers about 17 million square kilometers. That is roughly 11.5% of the entire Earth's land area. It is only smaller than deserts and xeric shrublands in total size.

The name "taiga" comes from the Russian word *tayga*. This term was historically used in Russia and northern Eurasia. It likely comes from Turkic or Mongolic roots. These roots refer to wooded or uninhabited forest lands. In North America, people often use the term "boreal forest." They sometimes use "taiga" specifically for the colder northern edges. In Eurasia, however, taiga usually refers to the entire biome. Scientists choose their names based on regional or academic traditions.

Climate is the most important factor in the taiga. It has a subarctic climate with massive temperature changes between seasons. The mean annual temperature is usually between −5 and 5 °C. In parts of eastern Siberia, the average temperature can drop to −10 °C. The coldest month in the Siberian taiga can reach −50 °C.

Summers are very short, lasting only one to three months. During these months, the 24-hour average temperature is 10 °C or more. Winters are much longer, lasting five to seven months. The long, cold winter is the most dominant feature of this environment.

The growing season is when the vegetation comes alive. In the taiga, this season is often longer than the actual summer. This happens because these plants can grow at lower temperatures than other species. A typical growing season might last around 130 days. In the Taiga Plains of Canada, it varies from 80 to 150 days.

High latitudes mean the sun stays above the horizon for a long time. In mid-summer, the sun may stay up for 24 hours. This provides many hours of light for plants to use. However, the sun stays low on the horizon. This means the plants receive less solar energy than they would further south.

Precipitation in the taiga is relatively low. Most areas receive between 200 and 750 mm of rain and snow annually. Some areas receive up to 1,000 mm. Most of this falls as rain during the summer. Snow can remain on the ground for nine months in the north.

Fog is also very common in low-lying areas. Fog can block sunshine even during long summer days. Because evaporation is low in the cold, the moisture stays in the ground. This allows for dense growth of large trees. This is different from the steppe biome, where evaporation is higher than precipitation.

The soil in the taiga is often young and lacks nutrients. The cold climate slows down the development of the soil. There are fewer deciduous trees to drop leaves every year. There are also fewer grazing animals to provide manure.

Fallen needles from evergreen trees make the soil acidic. This creates a specific type of soil called spodosol, or podzol. In very cold zones, continuous permafrost occurs. Permafrost is ground that stays frozen all year. This restricts trees to having very shallow roots. The Dahurian larch is a great example of a tree that handles this well.

Taiga can be divided into different types based on tree spacing. The southern part is a closed canopy forest. This means the trees are very close together. The ground is often covered in thick moss. The northern part is called lichen woodland or sparse taiga. In these areas, trees are farther apart. The ground is covered in lichen instead of moss.

In the northernmost areas, trees are often stunted or small. Some trees, like the black spruce, may grow in asymmetric shapes. This happens because of the harsh, biting winds. This variety of forest types shows how life adapts to extreme cold.

The taiga we see today is a relatively recent phenomenon. It has only existed for about 12,000 years. This began at the start of the Holocene epoch. Before this, the land was very different. In Eurasia, much of the area was under the Scandinavian Ice Sheet. In North America, the Laurentide Ice Sheet covered the land.

As these massive glaciers receded, they changed the landscape. They left behind depressions in the ground. These depressions filled with water to create lakes and bogs. These features are now common parts of the taiga ecosystem.