Transcript Grasslands - JBHA-Sci-US-tri1

Grasslands
By Mira Mooreville and Dana Gitlin
What is a grassland?
 Regions with enough average annual
precipitation to allow grass to prosper but
with precipitation so erratic that drought
and fire prevent large stands of trees
from growing.
Where are Grasslands?
Grasslands can be found on all
continents except Antarctica.
Climatogram
Three Main Types of
Grasslands
 Tropical
 Temperate
 Polar (tundra)
Tropical Grasslands
 Found in areas with high average
temperatures, low to moderate
precipitation, and a prolonged dry
season.
 They are widely spread on either side of
the equator beyond the borders of
tropical rain forests.
 A type of tropical grassland is a savanna.
Savannas
 Have warm temperatures
year round, two prolonged
dry seasons, and abundant
rain the rest of the year.
 Largest Savannas are
found in central and
southern Africa, but can
also be found in Central
South America, Australia,
and Southeast Asia.
Savanna Species
 Common Savanna animal species include wildebeests,
gazelles, zebras, giraffes, antelopes, cheetahs, lions,
hyenas, eagles, and hawks.
 Many large Savanna animal species are killed for their
economically valuable coats and parts (tigers), tusks
(rhinoceroses), and ivory tusks (elephants).
 Some Savanna plant species include Bermuda grass,
candelabra tree, elephant grass, gum tree eucalyptus,
whistling thorn, and river bush willow.
Temperate Grasslands
 Cover vast expanses of plains
and gently rolling hills in the
interiors of North and South
America, Europe, and Asia.
 Winters are bitterly cold,
summers are hot and dry, and
annual precipitation is fairly
sparse and falls unevenly
through the year.
 Types of temperate grasslands
are the tall-grass prairies and
short-grass prairies of the
midwestern and western US
and Canada, South American
pampas, African veldt, and
steppes of central Europe and
Asia.
Prairie
Prairie Species
 Common prairie animal species include
the American Bald Eagle, bobcat, bumble
bee, coyote, prairie dog, and swift fox.
 Some prairie plant species include big
bluestem grass, blue grama grass,
buffalo grass, milkweed, and stinging
nettle.
Food Web (Prairie)
Symbiotic Relationship
 Certain types of ants and aphids have a relationship
known as mutualism, a type of symbiosis, in which
species help each other to survive. Aphids, tiny slowmoving insects, live on plants. They feed on nectar,
which they suck out of plant stems with their long,
pointed mouths. As the aphids digest the nectar, it is
formed into a sugary substance called honeydew. The
aphids then release honeydew through specialized
organs called cornicles. Honeydew is one of the ants
favorite food. The ants eat as much honeydew as the
aphids can produce. The ants treat the aphids like their
own private heard. By keeping the aphids close to
them at all times, ants have a natural food supply.
Abiotic Factors of
Grasslands
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Soil
Sunlight
Water
Rocks
Air
Soil
 Aboveground parts of most of the grasses die and
decompose each year, allowing organic matter to
accumulate and produce a deep, fertile soil. The soil is
held in place by a thick network of intertwined roots of
drought-tolerant grasses.
 Because of their thick and fertile soils, temperate
grasslands are plowed up and widely used to grow
crops.
 The plowing however breaks up the soil leaving it
vulnerable to erosion by wind and water.
Major Human Impacts on
Grasslands
 Conversion of savanna and temperate
grassland to cropland.
 Release of carbon dioxide to atmosphere
from burning and conversion of grassland
to cropland.
 Overgrazing of tropical and temperate
grasslands by livestock.
Example of a Human
Impact
 Indian tribes and wildlife used to settle on the vast
grasslands of the Great Plains in the United
States. The settlers brought cattle and sheep which
grazed the plains. Settlers farmed the land and plowed
the topsoil. But in the 1930’s, there was an eight-year
drought which brought major wind and dust storms. As
a result, the soil became dry and loose and crops could
not grow. Because humans allowed the natural
grassland ecosystems to be overgrazed and
improperly utilized, the land was unable to endure such
a long drought. The government set up regulations to
help the farmers restore the land.
The Dust Bowl.
Environmental Damage
and Solutions
 Grasslands are adapted to high levels of animal impact by herds of
animals. Animal impact includes dunging, urinating, trampling,
rubbing, wallowing, salivating, etc. Their trampling and dunging is
extremely beneficial to the land and has maintained the grasslands
for millions of years. The beneficial effects of animal impact exist only
on high impact for a short duration. Low impact for a long duration
leads to environmental damage because plants and soils do not get a
chance to recover and restore itself, therefore becoming overgrazed.
 Animal impact maintains grasslands by:
 Planting seeds and guaranteeing good seed-to-soil contact
 Breaking soil crusts that obstruct the process of seed germination and
rainfall absorption
 Pruning plants to keep them fertile and active
 Eliminating weeds
 Mulching the soil surface with trampled vegetation, which protects it from
erosion and reduces soil surface evaporation
 Composting plant material
 Fertilizing the soil
Environmental Damage
and Solutions (cont’d)
 If grasslands do not have any animal impact, they will deteriorate,
especially in very dry areas. When grazing animals leave an
ecosystem, damage to the land will occur. Example: Nevada used to
be a grassland 100 years ago, but today it is mostly an arid desert.
 Animal impact is the most effective way known to renew the damaged
land and deserts.
 Today, animal impact is used worldwide to:
 Help vegetation in mine dumps in Nevada and Arizona, U.S.A.
 Restore desertified grasslands in South Africa, Zimbabwe, and the western
U.S.
 Control invasive weeds in South Africa, Oregon and Montana.
 Repair erosion damage in Mexico and California.
 Prevent soil-surface erosion in Australia
 Build new topsoil at rates of up to 1" per year
 Increase the ability of soil to absorb water in Australia, Africa, and New
Mexico.
 Encourage biodiversity in Australia, Africa and the western US.
Citations
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Textbook
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