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Grassland Biomes
CHAPTER EIGHT
Grass
 Looking outside at grass, you don’t usually think
much of it
 However, grass

Feeds billions of organisms worldwide
Bread and cereal
 Grains are domestic grasses
 Start of many food webs



Can survive temps from -25 to 70 degrees Celcius
Is the most widely distributed flowering plant
I Can…
 Describe the characteristics of grasslands
 Identify where grasslands are located
Grasslands
 A grassland is an ecosystem in which there is more
water than a desert, but not enough to support a
forest.
 Grasslands begin at the edges of the desert biome
and stretch to the forest biome.
 Grasslands in the US stretch from the Rocky
Mountains to the forests in the east, and from
Mexico to Canada.
Grassland Climate
 Grasslands are a little wetter than deserts.
 The desert-grassland boundary is the area between
deserts and grasslands where increased rainfall
enables some grasses to grow.
 Because rainfall is an abiotic factor, long-term
changes can change the boundary.

More rain creates more grassland, less rain creates more
desert.
Grassland Climate
 Other abiotic factors also affect the grassland
 Lightning
 Control burns

Both are the cause of fires that remove small trees and other
woody plants.
Grassland Organisms
 There are many organisms alive in grasslands, but
grasses are the most common.
 Grasslands have hot, dry summers, making rainfall
the most important limiting factor.
 Fires also play an important role in grassland
development.
Grassland Organisms
 The occasional fires common in the grasslands keep
the number of trees and shrubs low.
 Fires destroy trees and saplings because most of
their mass is above the ground and vulnerable.
 Grasses have most of their mass below ground.
 For example, one rye plant may have 2m above ground and
600 km (yes, kilometers) below ground!!
Grassland Organisms
 Another benefit of fires is that they burn away the
layer of dead grass that accumulates each year.
 This creates nutrients that feed the living grasses.
 Lastly, fires help some seeds to germinate and keep
grasses dominating the grassland.
Grassland Organisms
 Animals help maintain grasslands, too
 Grazing animals act as natural lawn mowers and
keep vegetation close to the ground.
 This limits the trees because they become too
damaged to grow well.
 Burrowing animals aerate the soil allowing oxygen
and water to access the root systems of grasses
quickly.
Grassland Organisms
 The amount of rainfall affects the sizes and textures
of the grasses that grow.
 Tall grass prairies and short grass prairies form
because of differences in rainfall and soil nutrients.
 Most tall grass prairies have been cleared for crops,
and many short grass prairies are now used for
grazing and irrigated crops.
Grassland Organisms
 Almost as important as how much rainfall an area
receives is when it rains.
 Some grasslands have rainy seasons followed by
drought.
 Grasslands with drought seasons have plants that
have adapted to be drought resistant.

Drought resistant plants survive despite small amounts of rain.
Grassland Organims
 All grasslands contain large grazing animals.
 Antelope and other grazing animals are often fast, an
adaptation that helps them avoid predators.

Grasshoppers and other insects feed on the seeds and leaves of
the grasses.

Many animals burrow underground and are only active at
night, avoiding predators and daytime heat.

In the US, grassland predators include: coyotes, foxes, snakes,
and birds.
Grassland Organisms
 Grasslands across the world vary by climate and
types of organisms.
 Scientists don’t always agree on how to classify
grasslands, but many divide them into three
different biomes:



Steppe
Prairie
Savanna
I Can…
 Compare and contrast a steppe and a prairie.
 Describe the importance of steppes and prairies in
agriculture.
Steppes and Prairies
 Steppes are similar to deserts in many ways.
 Steppes are grasslands of short bunchgrass that get
less than 50cm of rain a year.
 Plants and rain are sparse.
 In the US, steppes are located at the western and
southwestern edges of grasslands.
Steppes and Prairies
 Prairies make up most of the grasslands in the US.
 Prairies are grasslands characterized by rolling hills,
plains, and sod-forming grasses.
 In the US, prairies are called the Great Plains, but
they are called many names around the world.

Veldt, pampas
Steppes and Prairies
 The prairies of the world are large, fertile areas
where the human population gets most of its food.
 Because breads and cereals come from grains grown
on the prairies, they are often called “breadbaskets”.
Steppe and Prairie Climate
 To distinguish between steppe and desert, scientists
define a desert as receiving less than 25cm of rain
and the steppe as receiving 25 cm or more.
 Most of the rain on the steppe evaporates or only
saturates the upper 25cm (10in) of soil.
 High winds and temperatures are responsible for
evaporation.
 Temps can fall to -5 and soar to 30 degrees Celsius.
Steppe and Prairie Climate
 The amount of rain in the prairie is 50 to 75cm a year
 Occasionally there will be a year that the amount of
rainfall can be up to double this amount.
 Most often the rain comes in thunderstorms during
the rainy season.
Steppe and Prairie Organisms
 Soil in the prairie can hold water very well.
 Most of the grasses in the prairie have roots that
form a mat in the soil.
 This mat of soil and roots and called sod.
 Grasses that form this mat are called sod-forming
grasses.
Steppe and Prairie Organisms
 An example of a sod-forming grass is a lawn.
 When the soil is held together well as it is with these
plants and their root systems, it dries slowly.
 As the roots of the grasses die, they form a layer of
organic matter called humus. (who-miss, not like
hummus that you eat)
 Humus helps hold in moisture and nutrients for
grasses.
Steppe and Prairie Organisms
 Steppes are sometimes referred to as short grass
prairies.
 Most of the grasses short, fine-bladed grasses that
grow in a clump, called bunchgrasses.
 Clumping helps save water by having a small root
area under the shade of leaves.
 The short, fine blades of the bunchgrasses prevent
moisture loss, also.
Steppe and Prairie Organisms
 The roots of the steppe grasses may only go 50cm
deep.
 At this depth, they can absorb as much water as
possible before it quickly evaporates.
Steppe and Prairie Organisms
 Animals of the steppe and prairie have adapted by
migrating, hibernating, or burrowing underground.
 Plants have also adapted by using the energy present
in the wind to scatter seeds and pollen.
 When it gets too dry or cold, the grasses do not do
well and growth slows or stops.
Steppe and Prairie Organisms
 In colder areas, some of the animals hibernate, while
others migrate to another location.
 During hot periods animals will remain in burrows
to avoid the heat (prairie dogs).
Steppe and Prairie Organisms
 Prairie grasses are only slightly affected by grazing
animals.
 Poor farming and ranching practices hurt the steppe
and prairie more than the grazing animals.
 One harmful practice is allowing farm animals to
overgraze.
 This can begin the steps to desertification.
Steppe and Prairie Organisms
 When desertification begins, bigger problems can
develop.
 In the 1930’s overgrazing and droughts led to the
“dust bowl”.
 US farmers have since developed techniques to
reduce the impact on these ecosystems and hopefully
prevent another problem.
Steppe and Prairie Organisms
 Many farmers are replacing native species with
agricultural species.
 Bison, deer, wolves and grizzly bears used to be very
common in the grasslands of the US, but have been
replaced because of humans need for space and food.
 These animals have been replace with fields of corn,
wheat, grazing cattle and sheep.
 Without monitoring, these areas could become more
like deserts or semiarid scrublands.
I Can…
 Describe savannas, and state where they are located.
 Explain how organisms have adapted to survive on
the savanna
Savannas
 Savannas are tropical or subtropical grasslands
ranging from dry scrubland to open woodland.
 There is no savanna in the US.
Savanna Climate
 Rainy seasons and long periods of drought are
typical of savannas.
 The amount of rain can be 150cm, but most of it falls
during short rainy seasons.
 In Africa, the rainy season is from Jan-Apr.
Savanna Organisms
 In order to survive, the plants in the savanna must be
resistant to drought, fire, and grazing animals.
 Many plants grow runners, or long horizontal stems
above or below the ground.
 Runners can be used to reproduce; they spread
quickly and can run for several meters.
 Underground runners are protected during fires.
Savanna Organisms
 Savanna grasses grow in tufts, or large clumps of tall,
coarse grasses.
 Trees and shrubs have thorns or sharp leaves to
protect them from being eaten by grazing animals.
 Another adaptation, is that plants grow quickly here.
 The plants then recover quickly from damage.
Savanna Organisms
 The concentration of animals in small areas is also a
characteristic of the savanna.
 Animals will gather around streams and watering
holes while water is available.
 Because of this concentration of animals, there is a
vertical feeding pattern, or animals eat vegetation at
different heights.
 This reduces competition for food.
Savanna Organisms
 In Africa, lions, cheetahs, and other predators prey
on migrating herds of wildebeests, zebras, and some
antelope.
 Large animals migrate to where the rain has fallen
on the savanna.
 Sometimes habitat is lost because of human
activities, and in some cases wildlife preserves have
been set up to help preserve many species.