Ecology Biomes

Chapter 2

desert

• major bands at 30°N and 30°S latitude

  • occupy about 20% of earth’s land surface

• water loss usually exceeds precipitation

• soil usually extremely low in organic matter

• plant cover ranges from sparse to absent

• animal abundance low, but biodiversity may be high

  • strong behavioral adaptations

• humans tend to concentrate in oases and river valleys

• described as dry/arid

tundra

• covers most of lands north of Arctic Circle

• climate typically cold and dry with short summers

  • 200 to 600mm precipitation annually

• low decomposition rates

• dominated by perennial herbaceous plants

• supports high numbers of native mammals

• human intrusion historically low, but now increasing

• described as cold, bare, by arctic/antarctic

tropical rainforest

• most occur within 10° latitude of equator

• little temperature variation between months

• annual rainfall of 2,000 to 4,000mm relatively evenly distributed

  • quickly reaches soil nutrients

  • mycorrhizae help gather nutrients

• organisms add vertical dimension

• harbor staple foods and medicines for world’s human populations - increasingly exploited

• described as wet, humid, hot, bio-productive, diverse

biomes

major divisions of the terrestrial environment