GRASSLAND BIOMES
description
Transcript of GRASSLAND BIOMES
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