5.4.11: Boreal (Coniferous) Forests

Learning Objective

Recognize distinguishing characteristics of boreal (coniferous) forests & plant adaptations of the biome.

The boreal forest, also known as coniferous forest, is found roughly between 50^o and 60^o north latitude across most of Canada, Alaska, Russia, and northern Europe. Boreal forests in North America are sometimes referred to as Taiga. Boreal forests are also found above a certain elevation (and below high elevations where trees cannot grow) in mountain ranges throughout the Northern Hemisphere. This biome has cold, dry winters and short, cool, wet summers. The annual precipitation is from 40 cm to 100 cm (15.7–39 in) and usually takes the form of snow; little evaporation occurs because of the cold temperatures.

Though evergreen, the net primary productivity of boreal forests is relatively low, as is species richness. The aboveground biomass of boreal forests is high because these slow-growing tree species are long-lived and accumulate standing biomass over time. Boreal forests lack the layered forest structure seen in tropical rainforests or, to a lesser degree, temperate forests. The structure of a boreal forest is often only a tree layer and a ground layer. When conifer needles are dropped, they decompose more slowly than broad leaves; therefore, fewer nutrients are returned to the soil to fuel plant growth (Figure \(\PageIndex{1}\)).

Figure \(\PageIndex{1}\): The boreal forest has low lying plants and conifer trees. The snowcapped mountains of the Alaska Range are in the background. (credit: L.B. Brubaker, NOAA, Public Domain)

Adaptations

The long and cold winters in the boreal forest have led to the predominance of cold-tolerant cone-bearing plants. These are evergreen coniferous trees like pines, spruce, and fir, which retain their needle-shaped leaves year-round. These small, waxy leaves are adapted to little water loss during the winter where liquid water is not available.

Evergreen trees can photosynthesize earlier in the spring than deciduous trees because less energy from the Sun is required to warm a needle-like leaf than a broad leaf. Evergreen trees grow faster than deciduous trees in the boreal forest. In addition, soils in boreal forest regions tend to be acidic with little available nitrogen. Leaves are a nitrogen-rich structure and deciduous trees must produce a new set of these nitrogen-rich structures each year. Therefore, coniferous trees that retain nitrogen-rich needles in a nitrogen limiting environment may have had a competitive advantage over the broad-leafed deciduous trees.

Attributions

Curated and authored by Kammy Algiers using Terrestrial Biomes from Biology 2e by OpenStax (CC-BY). Access for free at openstax.org