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Grasslands and Tundra. Temperate grasslands Found in areas of moderate rainfall, typically between 25 and 75 cm per year. Dry seasons sufficient to exclude most trees. Frequent fires. North American grasslands are dominated by “bunch grasses.”.

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Presentation Transcript
slide2

Temperate grasslands

Found in areas of moderate rainfall, typically between 25 and 75 cm per year.

Dry seasons sufficient to exclude most trees.

Frequent fires.

slide5

The North American Great Plains can be divided into several prairie types. They differ primarily on the basis of the amount of rain and the time of the dry season.

slide9

Tundra ecosystems are found where cold, hard winds and/or permafrost prevent the growth of large woody plants. We recognize two types of tundra:

Arctic tundra

Alpine tundra

slide12

Alpine tundra is found high in mountains at all latitudes. Conditions are variable. Permafrost is rare.

slide13

Are grassland ecosystems equilibrium systems? This is significant in determining whether they will return if stresses are removed.

Some have suggested that they may have “multiple stable states.”

slide15

Population cycles are commonly seen in tundra habitats. They can be classified into three types:

  • 3-4 year cycles common in microtine rodents.
  • 9-10 year cycles as shown by snowshoe hares.
  • Longer cycles as seen in some larger tundra animals.
suggested causes of population cycles
Suggested Causes of Population Cycles
  • Herbivory hypothesis
  • Food supply-predation hypothesis
  • Predation hypothesis
slide20

Grazing impact of livestock is often due to selective herbivory.

Decreasers versus increasers

slide21

Invading species like cheatgrass (Bromius tectorum) has replaced native grasses over large areas.