1. CHAPTER EIGHT Grassland Biomes

2. Grass Looking outside at grass, you don’t usually think much of it However, grass  Feeds billions of organisms worldwide  Bread and cereal  Grains are domestic grasses  Start of many food webs  Can survive temps from -25 to 70 degrees Celcius  Is the most widely distributed flowering plant

3. I Can… Describe the characteristics of grasslands Identify where grasslands are located

4. Grasslands A grassland is an ecosystem in which there is more water than a desert, but not enough to support a forest. Grasslands begin at the edges of the desert biome and stretch to the forest biome. Grasslands in the US stretch from the Rocky Mountains to the forests in the east, and from Mexico to Canada.

5. Grassland Climate Grasslands are a little wetter than deserts. The desert-grassland boundary is the area between deserts and grasslands where increased rainfall enables some grasses to grow. Because rainfall is an abiotic factor, long-term changes can change the boundary.  More rain creates more grassland, less rain creates more desert.

6. Grassland Climate Other abiotic factors also affect the grassland  Lightning  Control burns  Both are the cause of fires that remove small trees and other woody plants.

7. Grassland Organisms There are many organisms alive in grasslands, but grasses are the most common. Grasslands have hot, dry summers, making rainfall the most important limiting factor. Fires also play an important role in grassland development.

8. Grassland Organisms The occasional fires common in the grasslands keep the number of trees and shrubs low. Fires destroy trees and saplings because most of their mass is above the ground and vulnerable. Grasses have most of their mass below ground.  For example, one rye plant may have 2m above ground and 600 km (yes, kilometers) below ground!!

9. Grassland Organisms Another benefit of fires is that they burn away the layer of dead grass that accumulates each year. This creates nutrients that feed the living grasses. Lastly, fires help some seeds to germinate and keep grasses dominating the grassland.

10. Grassland Organisms Animals help maintain grasslands, too Grazing animals act as natural lawn mowers and keep vegetation close to the ground. This limits the trees because they become too damaged to grow well. Burrowing animals aerate the soil allowing oxygen and water to access the root systems of grasses quickly.

11. Grassland Organisms The amount of rainfall affects the sizes and textures of the grasses that grow. Tall grass prairies and short grass prairies form because of differences in rainfall and soil nutrients. Most tall grass prairies have been cleared for crops, and many short grass prairies are now used for grazing and irrigated crops.

12. Grassland Organisms Almost as important as how much rainfall an area receives is when it rains. Some grasslands have rainy seasons followed by drought. Grasslands with drought seasons have plants that have adapted to be drought resistant.  Drought resistant plants survive despite small amounts of rain.

13. Grassland Organims All grasslands contain large grazing animals.  Antelope and other grazing animals are often fast, an adaptation that helps them avoid predators.  Grasshoppers and other insects feed on the seeds and leaves of the grasses.  Many animals burrow underground and are only active at night, avoiding predators and daytime heat.  In the US, grassland predators include: coyotes, foxes, snakes, and birds.

14. Grassland Organisms Grasslands across the world vary by climate and types of organisms. Scientists don’t always agree on how to classify grasslands, but many divide them into three different biomes:  Steppe  Prairie  Savanna

15. I Can… Compare and contrast a steppe and a prairie. Describe the importance of steppes and prairies in agriculture.

16. Steppes and Prairies Steppes are similar to deserts in many ways. Steppes are grasslands of short bunchgrass that get less than 50cm of rain a year. Plants and rain are sparse. In the US, steppes are located at the western and southwestern edges of grasslands.

17. Steppes and Prairies Prairies make up most of the grasslands in the US. Prairies are grasslands characterized by rolling hills, plains, and sod-forming grasses. In the US, prairies are called the Great Plains, but they are called many names around the world.  Veldt, pampas

18. Steppes and Prairies The prairies of the world are large, fertile areas where the human population gets most of its food. Because breads and cereals come from grains grown on the prairies, they are often called “breadbaskets”.

19. Steppe and Prairie Climate To distinguish between steppe and desert, scientists define a desert as receiving less than 25cm of rain and the steppe as receiving 25 cm or more. Most of the rain on the steppe evaporates or only saturates the upper 25cm (10in) of soil. High winds and temperatures are responsible for evaporation. Temps can fall to -5 and soar to 30 degrees Celsius.

20. Steppe and Prairie Climate The amount of rain in the prairie is 50 to 75cm a year Occasionally there will be a year that the amount of rainfall can be up to double this amount. Most often the rain comes in thunderstorms during the rainy season.

21. Steppe and Prairie Organisms Soil in the prairie can hold water very well. Most of the grasses in the prairie have roots that form a mat in the soil. This mat of soil and roots and called sod. Grasses that form this mat are called sod-forming grasses.

22. Steppe and Prairie Organisms An example of a sod-forming grass is a lawn. When the soil is held together well as it is with these plants and their root systems, it dries slowly. As the roots of the grasses die, they form a layer of organic matter called humus. (who-miss, not like hummus that you eat) Humus helps hold in moisture and nutrients for grasses.

23. Steppe and Prairie Organisms Steppes are sometimes referred to as short grass prairies. Most of the grasses short, fine-bladed grasses that grow in a clump, called bunchgrasses. Clumping helps save water by having a small root area under the shade of leaves. The short, fine blades of the bunchgrasses prevent moisture loss, also.

24. Steppe and Prairie Organisms The roots of the steppe grasses may only go 50cm deep. At this depth, they can absorb as much water as possible before it quickly evaporates.

25. Steppe and Prairie Organisms Animals of the steppe and prairie have adapted by migrating, hibernating, or burrowing underground. Plants have also adapted by using the energy present in the wind to scatter seeds and pollen. When it gets too dry or cold, the grasses do not do well and growth slows or stops.

26. Steppe and Prairie Organisms In colder areas, some of the animals hibernate, while others migrate to another location. During hot periods animals will remain in burrows to avoid the heat (prairie dogs).

27. Steppe and Prairie Organisms Prairie grasses are only slightly affected by grazing animals. Poor farming and ranching practices hurt the steppe and prairie more than the grazing animals. One harmful practice is allowing farm animals to overgraze. This can begin the steps to desertification.

28. Steppe and Prairie Organisms When desertification begins, bigger problems can develop. In the 1930’s overgrazing and droughts led to the “dust bowl”. US farmers have since developed techniques to reduce the impact on these ecosystems and hopefully prevent another problem.

29. Steppe and Prairie Organisms Many farmers are replacing native species with agricultural species. Bison, deer, wolves and grizzly bears used to be very common in the grasslands of the US, but have been replaced because of humans need for space and food. These animals have been replace with fields of corn, wheat, grazing cattle and sheep. Without monitoring, these areas could become more like deserts or semiarid scrublands.

30. I Can… Describe savannas, and state where they are located. Explain how organisms have adapted to survive on the savanna

31. Savannas Savannas are tropical or subtropical grasslands ranging from dry scrubland to open woodland. There is no savanna in the US.

32. Savanna Climate Rainy seasons and long periods of drought are typical of savannas. The amount of rain can be 150cm, but most of it falls during short rainy seasons. In Africa, the rainy season is from Jan-Apr.

33. Savanna Organisms In order to survive, the plants in the savanna must be resistant to drought, fire, and grazing animals. Many plants grow runners, or long horizontal stems above or below the ground. Runners can be used to reproduce; they spread quickly and can run for several meters. Underground runners are protected during fires.

34. Savanna Organisms Savanna grasses grow in tufts, or large clumps of tall, coarse grasses. Trees and shrubs have thorns or sharp leaves to protect them from being eaten by grazing animals. Another adaptation, is that plants grow quickly here. The plants then recover quickly from damage.

35. Savanna Organisms The concentration of animals in small areas is also a characteristic of the savanna. Animals will gather around streams and watering holes while water is available. Because of this concentration of animals, there is a vertical feeding pattern, or animals eat vegetation at different heights. This reduces competition for food.

36. Savanna Organisms In Africa, lions, cheetahs, and other predators prey on migrating herds of wildebeests, zebras, and some antelope. Large animals migrate to where the rain has fallen on the savanna. Sometimes habitat is lost because of human activities, and in some cases wildlife preserves have been set up to help preserve many species.