Grasslands

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Grasslands
Grassland-an ecosystem in which there is more
water than in a desert, but not enough water to
support a forest
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• Grasslands start at the edge of desert biome and
  stretch across the land to the forest biome
• Found in Africa, central Asia, North America,
  South America, and Australia
• In US, they stretch from Rocky Mountains in west
  to forests of the East
• Stretch from Canada down to Mexico
• CLIMATE
• Wetter than deserts
• The dry air that blows over the east of the
  mountain to form deserts, eventually gains enough
  moisture for rain to fall
• Desert-grassland boundary-the area b/n deserts
  and grasslands where increased rainfall enables
  some grasses to grow
• Long-term climate changes can cause biome changes
• If enough rain falls, a desert can become a
  grassland
• If rainfall decreases enough, a grassland can
  become a desert

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• ORGANISMS
• Both abiotic and biotic factors determine what
  organisms live in grasslands
• Grasses are the most common
• ABIOTIC FACTORS
• Hot, dry summers
• Rainfall is the limiting factor
• w/out rain, grass wont develop
• Also, natural fires caused by lightning limit
  grassland development
• Fires are common and keep of trees and shrubs
  low
• Most mass of trees and shrubs are aboveground, so
  they are vulnerable to fire
• Grasses have most mass below ground, so they
  survive better
• Rye plant is 2 meters high, but has 600 km of
  roots below

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• Fires also benefit grasslands by burning dead
  grass layer, making it into valuable nutrients
• Nutrients create a fertilizer
• Grasslands have a deep, fertile soil
• Heat from fire helps germinate grass seeds
• BIOTIC FACTORS
• Grazing animals, ex bison, are lawn mowers
  keeping vegetation low to ground
• This keeps trees and shrubs too damaged to grow
  well
• Burrowing animal, ex earthworms, prairie dogs,
  and insects, make tunnels and dig.
• This aerates the soil, giving more oxygen and
  nutrients to the grasses growing roots
• Rain amounts affect size and texture of grasses
• Short-grass prairies receive less rain
• Used for cattle grazing and irrigated crops
• Tall-grass prairies receive more rain
• Used for tall crops like corn and wheat

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• When it rains is also important
• Grasslands have rainy seasons and drought seasons
• Experience cycles of heavy rain followed by long
  periods of little or no rain
• Many plants adapted by becoming
  drought-resistant-trees and shrubs that survive
  in dry grasslands despite small amounts of rain
• ANIMALS
• All grasslands have large grazing animals
  antelope and bison
• They can run quickly from predators
• Many animals feed on seeds and leaves of grass
  grasshoppers, mice, gophers, prairie dogs, birds
• Some animals are nocturnal to avoid predators and
  daytime heat,
• They burrow underground
• North American predators coyotes, foxes, snakes,
  and birds
• Grasslands can be three types of biomes steppe,
  prairie, savanna

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Types of Grasslands

• Steppes
• Grasslands of short bunchgrasses that gets less
  than 50cm of rain/year
• Must get more than 25cm rain/year or else its a
  desert
• Temperatures range b/n -5 degrees and 30 degrees
  Celcius
• Bunchgrasses-short, fine-bladed grasses that grow
  in a clump

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• Prairies
• Grasslands characterized by rolling hills,
  plains, and sod-forming grasses
• Most grains grow here to make breads and cereals
• 50-75 cm of rain/yr
• Have sod-forming grasses- grasses that form a mat
  of soil and roots
• This keeps soil close together and less moisture
  will evaporate
• Also has a humus layer-layer of organic matter
  made from dead roots of the grasses
• Humus provides fertile and moist layer

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• Savannas
• Tropical or subtropical grasslands ranging from
  dry scrubland to wet, open woodland
• Have rainy seasons and long droughts
• Up to 150 cm rain/yr during short rainy season
• Plants must be resistant to drought, fires, and
  grazing animals
• Plants have runners-long, horizontal stems above
  and below ground
• Grasses grow in tufts-large clumps of tall,
  coarse grasses
• Tufts help protect them from grazing animals
• Animals often eat in vertical feeding
  pattern-animals eat at different heights
• this allows many animals to feed in the same area