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Chapter 4

Chapter 4. Terrestrial Biomes & Aquatic Ecosystems. Terrestrial biomes. Named for predominant vegetation Also have characteristic animals. Boundaries?. No sharp boundaries between biomes Intergrades. Importance of climate.

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Chapter 4

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  1. Chapter 4 Terrestrial Biomes & Aquatic Ecosystems

  2. Terrestrial biomes • Named for predominant vegetation • Also have characteristic animals

  3. Boundaries? • No sharp boundaries between biomes • Intergrades

  4. Importance of climate • Prevailing climate is most important factor in determining what kind of biome will develop • Precipitation, temperature are most important

  5. Desert biomes • <10 inches (<25.4 cm) of rain per year • Cool • Temperate • Tropical

  6. Grassland biomes • 10-30 inches (25.4-76.2 cm) of rain per year • Tundra • Temperate grassland • Tropical savanna

  7. Forest biomes • >30 inches (>76.2 cm) of rain per year • Taiga or coniferous forest • Temperature deciduous forest • Tropical rain forest

  8. Aquatic ecosystems • Initial categories based on salinity • Freshwater • Marine • Estuary

  9. Freshwater - nonmoving • Standing waters • Lakes • Ponds • Significant stratification in community structure • Light • Temperature

  10. Freshwater - moving • Moving waters • Rivers • Streams • Communities change from headwaters (source) to mouth as environment changes

  11. Headwaters vs. mouth • Headwaters • Cool • High current velocities • Few nutrients • Mouth • Warmer • Slower • More turbid • More nutrients

  12. Marine • Vertical and horizontal changes • Light • Temperature • Nearshore • Open ocean

  13. Estuary • Freshwater rivers merge with oceans • Mixing zone • Very high productivity • Threatened by pollution

  14. Climatograph

  15. Climograph • Temperature, precipitation not sole determiners • Overlap among different biomes on plot suggests that other factors also are important • Seasonality of precipitation • Temperature fluctuations around mean • Soil composition (based on geology)

  16. Deserts • Lands where evaporation exceeds rainfall • High evaporation rate • 7-50X precipitation

  17. Deserts • Occur in 2 distinct belts between 15-35° N & S latitude • Result primarily from worldwide circulation of air masses (dry over deserts) • ~25% of world’s land mass

  18. True deserts • <10 inches of rain per year • Semi-deserts may have 2-3X that, but have high evaporation rates • Low humidity results in very hot days, but cool or cold nights • Life is keyed to rainfall events • Infrequent, but usually heavy when they occur

  19. Desert life • Plants, animals are either drought evaders or drought resistors

  20. Evaders • Plants survive dry periods as seeds, but germinate, grow, and reproduce after rainfall • Animals may hibernate (cold) or estivate (hot) • Dormancy during dry period • E.g., spadefoot toad emerges to reproduce in pools formed after rain • E.g., birds migrate in and out

  21. Resistors - plants • Plants develop deep roots to become independent of rainfall events (woody shrubs) or are succulents to store water in stems (cactus)

  22. Resistors - animals • Behavioral adaptations • Come out only at night - spiders, scorpions, rodents, predators

  23. Resistors - animals • Physiological adaptations • No need to drink • Kangaroo rate with super kidneys gets all water from seeds

  24. Grasslands • Tropical savannas - grasslands with scattered individuals trees • Central S. Amer., Central & S. Africa

  25. Savannas • 3 distinct seasons • Cool-dry, hot-dry, warm-wet • Frequent fires suppress trees, maintain grasses and forbs • Herbaceous, low-growing annuals & perennials (dicots) • Regrow from roots or seeds every year

  26. Savannas • Large herbivores (zebras, giraffes) and burrowing animals most common • Most active during the rainy season

  27. Temperate grasslands • Similar to tropical savanna, but occur in cooler regions • N. Amer. prairie (French for plains) • Russian steppe • Hungarian pusztas • S. Amer. pampas • African veldt

  28. Temperate grasslands • At one time covered 42% of world land surface • Much under cultivation today • Excellent soils • Rich topsoil layer

  29. Temperate grassland climate • High rates of evaporation • Periodic severe drought • Rainfall ~25-75 cm/year • Too light to support forest, but too heavy to encourage desert

  30. Temperate grassland grasses • Sod-forming • Kentucky bluegrass • Bunch grasses • Big, little bluestem

  31. Temperate grasslands • Most require periodic fires for maintenance, renewal, elimination of incoming/invading woody growth • Animal life dominated by grazing and burrowing species

  32. Tundra • Northernmost limits for plant growth, and at high altitudes • Plants generally low-growing • Mat or shrubby

  33. Arctic tundra • Encircles north pole • Brief warm summers with nearly 24 hrs of sun/day • Presence of permafrost • Water-logged soils - low evaporation • Shrubs, sedges grasses, mosses, lichens

  34. Alpine tundra • At high elevations at all latitudes • Variable daylength, many of the same restrictions, plant species

  35. Tundra animals • Migratory, well-suited for cold climate • Musk oxen, caribou, reindeer • Lemmings, white fox, snowy owl

  36. Tropical forests • Equatorial, mean temp. ~25°C, 12 hrs sunlight per day • Rainfall highly variable-determines type of tropical forest present

  37. Types of tropical forests • Thorn forests - furthest from equator, prolonged dry season

  38. Types of tropical forests • Tropical deciduous forest • More rainfall nearer equator, distinct wet, dry seasons • Lose leaves during dry seasons

  39. Types of tropical forests • Tropical rain forest • >250 cm of rain per year • Perpetual midsummer conditions • Uninterrupted plant growth

  40. Tropical rain forests • Contain as many species of plants and animals as all other types of ecosystems combined • 4 mi2 area - 750 species of trees, 1500 species of flowering plants

  41. Tropical rain forests • Typically stratified into 5 layers • Each layer has characteristic plants, animals • May reach height of 80 m

  42. Tropical rain forest soil • Very poor - little or no topsoil • Easily weathered • Subsoil with iron-based clay - laterite • Major problems with slash-and-burn agriculture

  43. Tropical rain forests today • Deforestation

  44. Deforestation • Loss of forests at present rate will mean disappearance within next 15-25 years • Major problems will result from climate change, loss of species of medicinal, economic importance

  45. Temperate deciduous forest • Eastern N. Amer, N. Europe and east • Moderate temps., moderate moisture levels • 5-6-month growing season

  46. Temperate deciduous forest • Dominated by broad-leaved deciduous trees • Relatively nutrient-rich soil provides for good growth • Typically have 4 layers present • Ground, shrub, sapling, canopy • Rich diversity of plant, animal life

  47. Taiga • Boreal forest, coniferous forest • Harsh winters with lots of snow

  48. Taiga • Dominated by conifers - spruce, pine, fir, hemlock • Best suited for short growing season because they are not deciduous • Can carry out photosynthesis whenever temps. rise above freezing • Needle shape, waxy cuticle conserve moisture

  49. Taiga soils • Thin, acidic, develop slowly • Pine needles break down slowly in cool climate

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