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Biomes Major ecosystems found in large geographic regions characterized by a distinct vegetative

Biomes Major ecosystems found in large geographic regions characterized by a distinct vegetative community. --primarily a result of abiotic processes. Physiognomy The overall appearance of a biome or community based on the relative density, height, and shape of its dominant vegetation.

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Biomes Major ecosystems found in large geographic regions characterized by a distinct vegetative

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  1. Biomes Major ecosystems found in large geographic regions characterized by a distinct vegetative community --primarily a result of abiotic processes Physiognomy The overall appearance of a biome or community based on the relative density, height, and shape of its dominant vegetation

  2. Six major biomes: 1. tropics: 0-10º 2. grasslands/savannah: 10-40º 3. deserts: 30º 4. temperate forests: 30-45º 5. coniferous forests or taiga: 60º 6. tundra: 60-90º

  3. Fig. 27.5 (EFB)

  4. Tropical Biomes: • Most occur within 10° latitude of the of the equator • Defined by rainfall > 240 cm per year • Temperature and moisture not limiting factors, nutrients and light are

  5. Amazon (Neotropics) SE Asia Congo Old World New World

  6. Physiognomy of Tropics • high diversity of trees • 400-700 trees per hectare (2.47 acres) • 100-200 species represented • low population densities for each • dense canopy, stratified up to four levels

  7. High light attenuation Humidity ~70% Temperature warmer cooler 90-95% Fig. 29.27 (EFB)

  8. leaf with drip tip

  9. Leaf litter accumulates rapidly, but also decays rapidly Plants in competition for nutrients released by decay

  10. Gaps and patch dynamics

  11. Nurse tree with successional stages of growth to obtain nutrients released from decaying wood

  12. Temperate rain forest: Olympic National Park, WA

  13. Nurse Tree

  14. Deserts are defined by rainfall: • true desert has < 12 cm/yr • extreme desert < 7 cm/yr • semi-desert has up to 40 cm/yr • evaporation exceeds rainfall

  15. Deserts also characterized by: • hot days, cool nights from high albedo • sparse plant life • C4 and CAM photosynthesis • xerophytes • more living plant biomass below ground than above, sometimes 1:10 difference

  16. Four major North American Deserts Sonoran

  17. Sonoran Desert Lowest, hottest desert up to 120° F in summer Bi-annual rainfall ~18 cm/yr Most diverse desert in NA Saguaro Cactus limited by temperature

  18. Sonoran Desert, AZ cholla cactus ocotilla palo verde trees

  19. Four major North American Deserts Mohave Sonoran

  20. Most precipitation in winter 5-12 cm/yr Higher elevation than Sonoran Plants adapted to cooler temperatures Mohave Desert

  21. Joshua Trees

  22. Four major North American Deserts Mohave Sonoran Chihuahuan

  23. Most precipitation in summer 15-20 cm/yr Dominated by low shrubs and cactus Chihuahuan desert and creosote

  24. Prickly Pear Cactus

  25. Four major North American Deserts Great Basin Mohave Sonoran Chihuahuan

  26. Largest U.S. desert, considered a cold desert Elevations range from 5000-6000 feet Caused by a series of rainshadow effects Precipitation 15-25 cm/yr Dominated by sagebrush Great Basin Desert

  27. Sagebrush dominates

  28. Desert ‘pavement’

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