1. Ecology Grasslands Chapter 8 Notes

2. I. Grasslands An ecosystem in which there is more water than a desert, but not enough water to support a forest They stretch from the edge of the desert across the land to the forest biome In the United States, they stretch from the Rocky Mountains in the west to the forest in the east, and from Canada to Mexico

3. Tall-grass prairies and short-grass prairies of the mid western and western United States and Canada form because of differences in rainfall and soil nutrients –Tall-grass prairies: have fertile soil that can support grasses up to 2 meters tall Most of them have been cleared for crops such as corn and wheat –Short-grass prairies: have less fertile soil and are mostly used for cattle grazing and irrigated crops

4. II. Grassland Climate Slightly more wet than that of deserts –Desert grassland boundaries- area between deserts and grasslands where increased rainfall enables some grasses to grow If rainfall increases in a desert, it can become a grassland If the climate of grasslands becomes to dry it can become a desert – because it can no longer support the organisms that usually live there They have hot, dry summers Rainfall is the most significant limiting factor

5. Although the amount of rain an area receives is important to the ecosystem as well as the time when it rains Grasslands experience cycles of rainfall which help determine the types of organisms that live there: –Rainy seasons- cycles of heavy rain –Drought seasons- long periods of dryness

6. B. Grassland organisms Types of organisms are determined by abiotic and biotic factors of the grassland ecosystem Grasslands have many different types of organisms that live there… –Grasses are the most common Occasional grass fires, ignited by lightning, also play an important role in the development of grasslands

7. –Occasional fires keep the number of trees and shrubs low cause most of their mass is above ground making them more vulnerable »Most of grasses mass is below ground which helps them survive the fires as well as low rain periods –fires remove species that compete with grasses for resources –Another benefit is that they burn away layers of dead accumulated grasses converting it into valuable nutrients –Heat from the fires also aids in the germination of grass seeds Another affect on grasslands are animals –Grazing animals act as natural lawn mowers, keeping the vegetation close to the ground –Animals such as earthworms, prairie dogs, and insects, aerate the soil by burrowing, tunneling and digging »This aeration of the soil helps grasses to grow better because the nutrients, oxygen and water can reach the roots quicker and easier

8. All grasslands contain large grazing herbivores such as antelope and bison Small herbivores, such as mice, gophers, prairie dogs and birds as well as other insects such as grasshoppers feed on the seeds and leaves of grasses Predators in the grasslands differ throughout the world –Most common types and top consumers in the North American Prairies are: Coyotes, foxes, snakes, & birds of prey

9. C. Biome types All grasslands around the world can be divided into 3 biomes depending on climate and types of organisms present: –Steppe –Prairie –Savanna

10. II. Steppe characteristics Grasslands of short bunchgrasses that get less than 50 cm of rain a year –Rainfall very low –Plant life is sparse –Some consider steppes to be semiarid deserts rather than grasslands To distinguish between…deserts receive less than 25 cm rainfall each year and steppes receive more than 25 cm per year

11. A.) Steppe Climate –Most rainfall evaporates quickly or only reaches the upper 25 cm of soil Due to high temperature and heat –Temperatures can fall below-5 degrees C and get as high as 30 degrees C

12. B. Steppe Organisms Sometimes referred to as short grass prairies Grasses of the steppes are mostly bunchgrasses –Short fine-bladed grasses that grow in a clump The clumping helps save water by holding it in the small root area under the shade of the grass Animals have adapted to changing conditions by migrating, hibernating, and burrowing underground

13. III. Prairie Characteristics Grasslands of characterized by rolling hills, plains, and sod-forming grasses Large, fertile areas where human population gets most of its food –Grains are most common crop grown here giving us breads and cereals so they are sometimes called “breadbaskets” Most commonly known as the “Great Plains” Make up most grasslands of United States

14. A. Prairie Climate Receives about 50 to 75 cm of rain each year

15. B. Prairie Organisms Most grasses here have roots that form a mat in the soil –Sod- the mat of soil and roots –Sod-forming grasses- grasses that form a mat of soil and roots The soil is fertile because organisms aerate it creating air spaces where water can be held and the soil benefits from humus –Humus- decomposed matter from plants and animals that forms a layer of organic matter which provides nutrients and helps hold water

16. IV. Animals of both the steppe and prairies They have adapted to changing conditions of the grasslands by migrating, hibernating and burrowing underground

17. V. Farming practices Poor farming and ranching practices can cause extensive damage to the grasses of both steppes and prairies –Concentrated feeding of grazing animals in small areas is very harmful this is called overgrazing Overgrazing- when grazing animals eat too much in one place destroying most of the grasses Many farmers are replacing native grasses with specialized species of grasses for agriculture purposes as well as the native animals (bison, deer, wolves and grizzly bears) with huge herds (cattle and sheep)

18. VI. Savannas Tropical or subtropical grasslands ranging from dry scrubland to wet, open woodland Found in Asia, Africa and parts of South America

19. A. Savanna Climate Typically has rainy seasons with long periods of drought –Rain amount can be as high as 150 cm a year, but most of it falls heavily during thunderstorms in short rainy seasons –In Africa, the rainy season is usually from January to April

20. B. Savanna Organisms In order for plant organisms to survive in the savanna they must be resistant to drought, fire and grazing animals Many plants of the savanna grow runners –Runners- long horizontal stems above or below ground They are used by some plants to reproduce, they spread quickly and extend several meters Savanna grasses grow in tufts –Tufts- large clumps of tall, coarse grasses

21. Other adaptations of plant organisms: –They have thorns and sharp leaves to protect them from being eaten –Ability to grow rapidly which enables them to recover quickly from damage caused by fires or animals This also gives them a better chance to use available water that falls during short rainy seasons Animals concentrate around watering holes during rainy seasons and this causes them to use available food in a system known as vertical feeding pattern –Vertical feeding pattern- when the animals eat vegetation at different heights This enables animals with different eating habits to feed in the same area without competing for food