GRASSLAND BIOMESENVIRONMENTAL SCIENCE - CHAPTER 8

GRASSLANDS

Grasses feed thousands all over the world.

Grasses are found on every continent on Earth.

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

more rain = tall/broad-leaf grasses

• 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 FactsSteppes – 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 horselemming

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

Towns help aerate the soil

Prairie chicken

Bison

Prairie fox

Prairie dogs

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