Temperate Grasslands and Deciduous Forests

Temperate grasslands are mid-latitude biomes dominated by grasses, with 250–750 mm of rain a year, hot summers and cold winters, while temperate deciduous forests are mid-latitude forests of broadleaved trees that shed their leaves in autumn, with about 750–1,500 mm of rain and four distinct seasons. In brief: grasslands (prairies, steppes, pampas and veld) have deep, fertile soils and are mostly turned into farmland; deciduous forests (oak, beech, maple) have layered vegetation and brown soils made fertile by leaf litter. Both biomes have been heavily altered by agriculture and settlement.

These two biomes cover some of the most densely populated and productive regions of the world. This guide explains the climate, vegetation, soils and wildlife of each, compares them in a table, works through calculations on seasons and litter, outlines how humans have changed them and corrects common mistakes.

What are temperate grasslands?

Temperate grasslands lie in the interiors of continents, far from the sea, where rainfall is too low for forest but too high for desert. Regional names include the prairies of North America, the steppes of Eurasia, the pampas of Argentina and Uruguay and the veld of southern Africa. Summers are warm to hot and winters can be very cold, with a large annual temperature range. Rain falls mostly in late spring and summer, and droughts, fire and strong winds are common.

How do grassland plants, soils and animals work?

Grasses, such as buffalo grass and feather grass, grow from the base, so grazing and fire do not kill them, and their roots can extend 1 to 2 m or more into the soil. When roots die each year, they add large amounts of organic matter, producing very fertile, dark soils called chernozems (in Eurasia) or mollisols (in the USDA classification). These are among the best farmland soils in the world.

Large grazers, such as the American bison, pronghorn and Eurasian saiga, live in herds, and burrowers such as prairie dogs and ground squirrels shelter underground. Birds nest on the ground. Much of the original grassland has been plowed for wheat, maize and other grains or used for cattle ranching, and only small fragments remain in a natural state in some regions.

What are temperate deciduous forests?

These forests occur where rainfall is moderate and well distributed and where winters are cool but not extreme: eastern North America, Western and Central Europe, East Asia (China, Korea, Japan), and small areas in the southern hemisphere. Average temperatures range from about 0 °C in winter to 20 °C or more in summer. The growing season lasts about 5 to 7 months. Trees shed their leaves in autumn to avoid water loss and frost damage when the ground is frozen and roots cannot absorb water. Before the leaves fall, the tree withdraws chlorophyll, which reveals the yellow, orange and red pigments seen in autumn color.

How do forest layers, soils and animals work?

A deciduous forest has several layers: the tree canopy (oak, beech, maple, ash, birch), a shorter understory of small trees, a shrub layer, an herb layer with spring flowers such as bluebells, and a ground layer of mosses and litter. Many spring flowers bloom early, before the canopy closes and blocks the light. In autumn, leaf litter falls and decays, returning nutrients to the soil, which results in fertile brown earth soils that are the basis for much of Europe’s farming.

Animals are adapted to the seasons: some hibernate (bears and hedgehogs), some migrate (many birds) and others store food (squirrels). Deer, foxes, badgers, wolves in some areas, owls and many insects are typical. Most original deciduous forest has been cleared for farmland and towns over centuries, and what remains is mostly secondary growth or managed woodland.

Grassland and forest compared

Worked example: seasons and litter

1. Temperature range: a steppe site has a July mean of 22 °C and a January mean of −14 °C. The annual range is 22 − (−14) = 36 °C, much larger than at a coastal forest site with 18 °C and 3 °C, which has a range of 15 °C.
2. Growing season: a forest has an average of 190 frost-free days, which is 190 ÷ 365 = 52% of the year.
3. Leaf litter (hypothetical): a forest produces 4 tonnes of litter per hectare each year, and the floor holds 6 tonnes. If the input equals the decomposition in a steady state, the litter turns over in 6 ÷ 4 = 1.5 years.
4. Grassland conversion: a grassland region of 800,000 km² has lost 70% to farmland. The remaining area is 800,000 × 0.30 = 240,000 km².
5. Farm yield: if a wheat field of 2,500 ha yields 3.2 tonnes per hectare, the harvest is 2,500 × 3.2 = 8,000 tonnes.

How have humans changed these biomes?

Grasslands were once grazed by huge herds and used by nomadic people. In the 19th century, steel plows, railways and settlement turned the North American prairies into farmland, and the Dust Bowl of the 1930s showed the risk of plowing dry grassland without protecting the soil. In Eurasia, large areas of steppe were plowed in the 1950s in the Soviet “Virgin Lands” campaign. European deciduous forests were cleared extensively from the Middle Ages, and by the 18th and 19th centuries only a fraction was left, though forest area has recovered in some countries since the 20th century. Conservation today includes national parks, restoration of prairie and sustainable forestry.

Which mistakes are common?

Mistake 1: Thinking that grasslands are empty and unproductive

They have enormous root systems below ground and very fertile soils, which is why they became major farming regions.

Mistake 2: Confusing the prairie, steppe and pampas

They are the same type of biome in different continents: North America, Eurasia and South America.

Mistake 3: Saying that trees lose leaves because of cold alone

Leaf fall is an adaptation to winter stress, mainly the lack of liquid water when the ground freezes and the low light.

Mistake 4: Assuming that deciduous forests are untouched

Most temperate deciduous forests have been cleared or managed for centuries, so little original forest remains.