Taiga & Boreal Forests
Taiga, sometimes called the coniferous forests are dominated by a low diversity of conifers. It is the largest biome in the world based upon landmass. This biomes may be a geologically recent biome, only forming within the last 12,000 years, replacing the Mammoth Steppe. The word "taiga" is Russian for forest.
Climate
A climate that is snowy, cold, with 4 months of a growing season
Rainfall
20 - 185 cm/yr
Temperature
Average annual between -5° and 5°C
Regional Expressions
northern North America and northern Eurasia
Soil
Thin, nutrient-poor, and acidic (spodosols)
Spodosols are characterized by high acidity, and have a subsoil accumulation of organic matter, along with aluminum and iron oxides, called a spodic horizon.
Typically low in natural fertility (basic cations, Ca2+, Mg2+, and K+) and high in soil acidity (H+, Al3+), these soils require extensive inputs of lime and fertilizers to be agriculturally productive.
Flora
Cold-tolerant evergreen conifers
Pine (Pinus), fir (Abies), and spruce (Picea) are common
Mosses and lichens are common as forest floor flora
A few deciduous angiosperms exist as forest edge and pioneer species (e.g. Populus)
Adaptations
Evergreen leaves
Reduced leaf area (See specialized leaves) such as needle-like leaves
Sunken stomata (See specialized leaves)
Hypodermis (See specialized leaves)
Deciduous leaves - a few angiosperms a deciduous in this biome (See specialized leaves)
Root suckers in some angiosperm trees
Above: A Whittaker Graph showing where the taiga occupies this abiotic space, based on precipitation and temperature
Evolution of the biome
The boreal forests dominated by conifers have been more common since the origin of the angiosperms in the Cretaceous, as many conifer taxa evolved to survive in higher latitudes and altitudes, away from angiosperm competition
Starting around 50 million years ago, the Earth has become progressively colder compared to the Mesozoic, and conifers became more prominent in higher latitudes and altitudes
During the Neogene, coniferous forests expand in many areas as the Earth became colder with glaciations
The taiga, in its current form, may have only formed within the last 12,000 years, replacing the Mammoth Steppe, after the extinction of the mammoth and other large herbivores
Additional Resources
The world’s boreal forests may be shrinking as climate change pushes them northward (3Nov2023 The Conversation)