Transcript Grasslands - HPE3rdGrade

Grasslands
Grassland-an ecosystem in which there is more water than in a
desert, but not enough water to support a forest
• 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
• 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 won’t 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
• 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
• 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
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
it’s a desert
• Temperatures range b/n -5 degrees and 30
degrees Celcius
• Bunchgrasses-short, fine-bladed grasses
that grow in a clump
• 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
• 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 patternanimals eat at different heights
• this allows many animals to feed in the same area