CHAPTER 8-1 Grasslands

Grasslands 1

CHAPTER 8-1 Grasslands

R. Bowman

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OBJECTIVES

• Describe the characteristics of grasslands• Identify where grasslands are located

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Grassland Climate

• Grassland - is an ecosystem in whichthere is more water than in a desert but notenough water to support a forest.

• Grasslands start at the edge of the desertbiome.

• They stretch across land to the forestbiome.

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Grassland Climate

• Grasslands exist in Africa, central Asia,North America, South America, andAustralia.

• In the U.S. grasslands stretch from theRocky Mountains in the west to the forestin the east, and from Canada to Mexico.

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Grassland Climate

• Grasslands are just a little wetter than theclimate of a desert.

• Desert-grassland boundary is the areabetween deserts and grasslands whereincreased rainfall enables grasses to grow.

• If rainfall increases, the desert canbecome grassland.

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Grassland Climate

• If rainfall stops, grassland can becomedesert.

CHAPTER 8-1 Grasslands

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Grassland Organisms

• The biotic and abiotic factors common toall grassland ecosystems determine whattypes of organisms will be found livingthere.

• Grasslands have hot, dry summers.• Rainfall is the limiting factor for a

grassland.

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Grassland Organisms

• Scientists have determined that naturalgrass fires, ignited by lightning, also playan important role in the development ofgrasslands.

• Grass fires destroy trees and shrubsbecause most of their mass is abovegroundand vulnerable to fire.

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Grassland Organisms

• Grasses have most of their massbelowground.

• One rye plant may grow 2 m tall but have600 km of roots belowground, protectedfrom fire and drought.

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Grassland Organisms

• Fires remove species that compete forresources with grasses.

• The fire also returns nutrients back to thesoil when dead grass is burned.

• Heat from the fire also aids in seedgermination of many grass seeds.

• Grazing animals, such as bison act likelawn mowers, keeping the grass low andtrees out.

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Fire

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Grassland Organisms

• Animals such as earthworms, prairie dogs,and insects aerate the soil by diggingtunnels.

• When soil is aerated, grasses grow betterbecause nutrients, oxygen, and water canreach the roots more quickly.

CHAPTER 8-1 Grasslands

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Grassland Organisms

• Most tall-grass prairies, that support 2 m tallgrass, have been cleared for crops such as cornand wheat.

• Short-grass prairies are now used for cattlegrazing and irrigated crops.

• Some grasslands experience cycles of heavy rainfollowed by long periods of little or no rain,called rainy seasons and drought seasons.

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Grassland Organisms

• Some trees and shrubs in grasslands oftengrow near ponds, streams, and springs.

• Many trees have adaptations that makethem drought-resistant.

• These trees and shrubs survive in the drygrasslands, despite small amounts of rain.

• All grasslands contain large grazinganimals such as antelope and bison.

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Grassland Organisms

• The ability to run quickly across theprairie is an adaptation that helps themavoid predators.

• Grasshoppers and other insects feed on theseeds and leaves of grasses, as do manyother small herbivores including mice,gophers, prairie dogs, and birds.

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Grassland Organisms

• Some of these animals burrowunderground and are only active at night,to avoid predators and intense daytimeheat.

• Predators in the grassland are differentthroughout the world.

• In North American prairies, coyotes, foxes,snakes, and birds of prey are the topconsumers.

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Grassland Organisms

• The grasslands of the world are dividedinto three different biomes– 1. steppe– 2. prairie– 3. savanna

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Steppe

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Steppe Map

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Prairie

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Prairie Map

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Savanna

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Savanna Map