Transcript grassland biomes

GRASSLAND BIOMES
ENVIRONMENTAL SCIENCE - CHAPTER 8
GRASSLANDS
 Grasses feed thousands all
over the world.
 Grasses are found on every
continent on Earth, except
Antarctica.
 All grains (wheat, rice,
oats) are grasses.
 Grasses can survive vast
temperature changes (from
-25oC to 70oC).
GRASSLAND DEFINED
 Grassland - ecosystem with
more water than a desert but
not enough to support a
forest
 Found in every continent
Africa, central Asia, North
America, South America,
Australia EXCEPT
Antarctica
 Desert-grassland boundary –
rainfall amount determines
whether land becomes desert
or grassland
Grassland Organisms
 Most common plants are
grasses
 Most of the grass plant is
underground (roots)
 This protects the grasses
from fire and drought.
Ex: A single rye plant can
grow as tall as 2 meters and
have roots spread out as far
as 600 km!
GRASSLAND FACTS
•
Rainfall is the most important abiotic
limiting factor.
•
Rainfall amount determines the kinds of
grasses and how tall they will grow.
Ex: less rain = short/fine-leaf grasses (Tundra)
more rain = tall/broad-leaf grasses
(Thailand)
•
Temperature ranges from -25oC to 70oC
•
FIRES
eliminate competing trees and shrubs
clear away all dead grasses that build up
release nutrients and minerals from the soil
help some grass seeds to germinate
Grassland Facts

Biotic factors can also affect
grassland organisms.
Ex: Large populations of grazing
animals will prevent trees and
shrubs from growing around a
grassland pond
Two seasons:
Rainy seasons – short cycles of
heavy rain
Drought seasons – longer periods of
little or no rain
Ex: Savanna in Africa has both
rainy and drought seasons
Steppe Facts
Steppes –
 gets less than 50 cm rain
per year -most rain
evaporates quickly
 found on western and
southwestern edges of
deserts
 Have high winds
 Broad temperature range
from -5oC to 30oC
Steppe Plants
• Bunchgrasses are short
fine-blade grasses that
grow in a clump
 Short fine blades of grass
and clumping the roots
prevent water loss
 Use high winds to help
disperse plant seeds to new
growing areas
 Roots can grow as deep as
50 cm
 Freeze resistant
Steppe Animals
 Adaptations to grassland
include migrating,
hibernating and burrowing
underground.
 Graze on grass late
afternoon to early morning
(hot) .
 Burrow underground
during the cold periods
 Migrate with the
availability of grasses
Mongolian horse
lemming
Bactrian camel
Steppe wildcat
Prairie Facts
 Grasslands characterized
by rolling hills, plains and
sod formation
 Rainfall is 50-75 cm per
year
 Soil holds water – grass
roots form mats with the
soil called sod
 When the sod grasses die
they form high nutrient
organic material called
humus
Prairie Plants
 Grasses form sod mats
 Hold water well
 Wind disperse grass seeds
 Grasses aren’t harmed by
large populations of
herbivores because of their
adaptation of migration.
Prairie Animals
 Prairies support large
populations of herbivores
 Animals use migration,
hibernation and burrowing
as adaptations to the
temperature extremes
 Prairie animals help the
prairie biome ecosystem.
Large populations of prairie
dogs (rodents) create
“towns”- a series of
connecting underground
burrows
Bison
Prairie chicken
Prairie fox
Prairie
dogs
 Towns help aerate the soil
Black-footed ferret
AMERICAN DUST-BOWL

1934-1938 an estimated 2.5
million people were forced to
leave their farms and ranches.

Major environmental disaster
(150,000 square miles of soil
loss, dust storms )

Causes: strong winds combined
with poor farming practices and
drought

Locations: Montana, North and
South Dakota, Oklahoma,
Kansas, Texas, Colorado, New
Mexico and Mexico
Savannas
 Tropical grasslands
ranging from dry
scrubland to wet, open
woodland.
 Mainly in central Africa,
with small areas in India,
southeastern Asia, northern
Australia, llanos in
Venezuela and Campos in
Brazil
 Short rainy seasons
followed by long periods of
drought
Savanna Plants

Plants must be resistant to heat, drought,
fires and grazing animals.

Adaptations include:
Rapid growth – savanna plants grow
quickly.
Runners – long horizontal stems above and
below the ground – plants spread quickly
and are protected from fire.
Tufts – are large clumps of tall coarse
grasses.
Thorns – trees and shrubs grow spike like
thorns or sharp leaves to prevent herbivores
from eating them.
Ex: Trees - Acacia, Baobab, Grasses - Rhodes, red
oak, elephant, star and lemon , Shrubs – aloe
candelabra tree
Baobab tree only has leaves in the short
rainy season.
Acacia trees grow leaves only at the top of
the branches and send out a chemical that
make the leaves inedible after a giraffe eats
one mouthful and one tree sends chemical
signals to warn he surrounding trees.
Savanna Animals
 Must take advantage of short
rainy season
 Adaptations:
Migrate with food availability
Reproduce during rainy
season
Vertical feeding pattern
animal height determines
what plants they eat this
allows many animals to
occupy smaller more specific
niches
Ex: lions, cheetah, springbok,
elephant, rhino, Weaver bird,
secretary bird