Grasslands
Grasslands are dominated by a rich mix of grasses and forbs (non-grass plants); herbaceous and non-woody plants. They have low precipitation rates and are maintained by fire which suppresses tree saplings. This biome becomes prominent during the Miocene epoch (23-5 Mya) due to a cooling, drying climate on Earth. Grasslands have very fertile soil, therefore they have been extensively converted to agriculture. When the soils of grasslands are compromised, these biomes frequently becomes deserts.
Climate
Warm to hot summers, with cold, windy winters
Rainfall
Precipitation in grasslands is relatively low, usually occurring in the late spring and early summer: 50.8 to 127 cm/yr (20-50 in/yr)
Precipitation is the major abiotic factor defining this biome, along with the presence of fire to suppress woody saplings
Temperature
The temperature range is very large over the course of the year
Summer temperatures can be well over 38°C (100°F),
Winter temperatures can be as low as -40°C (-40°F).
The entire biome has an average annual temperature between -10 and 20°C
Regional Expressions
North American Midwest, Eurasia, Argentina, Uruguay, South African veld
Above: A Whittaker Graph showing where grasslands occupy this abiotic space, based on precipitation and temperature
Soil
Some of the world's most fertile soils
Thick, woven root systems of grasses hold nutrients in place
There are members of the Fabaceae in grasslands that fix nitrogen, adding to the fertility of the soil
Low rainfall, prevents erosion and loss of nutirents
Fires constantly return organic material to the soils
Flora
Perennial grasses and perennial forbs
Asteraceae and Fabaceae common
Sod-forming and bunch grasses
Adaptations
Rhizome-bearing plants, such as grasses
Basal meristems, to avoid large herbivores
Fire-resistance in plants
C4 photosynthesis (see photosynthesis)
Bulliform cells in leaves
Wind-pollination in grasses
Large showy flowers in "forbs"
Evolution of the biome
The origin of grasslands is linked to the evolution of grasses (Poaceae)
The oldest evidence of grasses from 100–97 Ma from phytoliths in coprolites of titanosaurs
Early grasses may have been marsh-edge plants, and not forming grassland biomes at this point
It is assumed that grasslands, as a dry, fertile biome, becomes prominent around 30 million years ago (Oligocene Epoch)
Additional Resources
Danish grasslands are behaving strangely and researchers don't know why (Phys.org 21Feb2024)
└ Damgaard (2024) Decline in large-seeded species in Danish grasslands over an eight-year period
Plant diversity stabilizes soil temperature (Phys.org 6Dec2023)
└Huang et al. (2023) Enhanced stability of grassland soil temperature by plant diversity
Where the bison could roam (New York Times 10Jan2023)
Reintroducing bison on tallgrass prairie doubles plant diversity (Successful Farming 1Sep2022)
Reconstructing Two Centuries of Midwest Prairie Fire History (In Defense of Plants 28Nov2021)