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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

Chapter 4

Terrestrial Biomes & Aquatic Ecosystems

terrestrial biomes
Terrestrial biomes
  • Named for predominant vegetation
  • Also have characteristic animals
  • No sharp boundaries between biomes
  • Intergrades
importance of climate
Importance of climate
  • Prevailing climate is most important factor in determining what kind of biome will develop
    • Precipitation, temperature are most important
desert biomes
Desert biomes
  • <10 inches (<25.4 cm) of rain per year
  • Cool
  • Temperate
  • Tropical
grassland biomes
Grassland biomes
  • 10-30 inches (25.4-76.2 cm) of rain per year
  • Tundra
  • Temperate grassland
  • Tropical savanna
forest biomes
Forest biomes
  • >30 inches (>76.2 cm) of rain per year
  • Taiga or coniferous forest
  • Temperature deciduous forest
  • Tropical rain forest
aquatic ecosystems
Aquatic ecosystems
  • Initial categories based on salinity
    • Freshwater
    • Marine
    • Estuary
freshwater nonmoving
Freshwater - nonmoving
  • Standing waters
    • Lakes
    • Ponds
  • Significant stratification in community structure
    • Light
    • Temperature
freshwater moving
Freshwater - moving
  • Moving waters
  • Rivers
  • Streams
  • Communities change from headwaters (source) to mouth as environment changes
headwaters vs mouth
Headwaters vs. mouth
  • Headwaters
    • Cool
    • High current velocities
    • Few nutrients
  • Mouth
    • Warmer
    • Slower
    • More turbid
    • More nutrients
  • Vertical and horizontal changes
    • Light
    • Temperature
    • Nearshore
    • Open ocean
  • Freshwater rivers merge with oceans
    • Mixing zone
  • Very high productivity
  • Threatened by pollution
  • 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)
  • Lands where evaporation exceeds rainfall
  • High evaporation rate
    • 7-50X precipitation
  • 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
true deserts
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
desert life
Desert life
  • Plants, animals are either drought evaders or drought resistors
  • 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
resistors plants
Resistors - plants
  • Plants develop deep roots to become independent of rainfall events (woody shrubs) or are succulents to store water in stems (cactus)
resistors animals
Resistors - animals
  • Behavioral adaptations
  • Come out only at night - spiders, scorpions, rodents, predators
resistors animals24
Resistors - animals
  • Physiological adaptations
  • No need to drink
    • Kangaroo rate with super kidneys gets all water from seeds
  • Tropical savannas - grasslands with scattered individuals trees
    • Central S. Amer., Central & S. Africa
  • 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
  • Large herbivores (zebras, giraffes) and burrowing animals most common
  • Most active during the rainy season
temperate grasslands
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
temperate grasslands29
Temperate grasslands
  • At one time covered 42% of world land surface
  • Much under cultivation today
  • Excellent soils
    • Rich topsoil layer
temperate grassland climate
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
temperate grassland grasses
Temperate grassland grasses
  • Sod-forming
    • Kentucky bluegrass
  • Bunch grasses
    • Big, little bluestem
temperate grasslands32
Temperate grasslands
  • Most require periodic fires for maintenance, renewal, elimination of incoming/invading woody growth
  • Animal life dominated by grazing and burrowing species
  • Northernmost limits for plant growth, and at high altitudes
  • Plants generally low-growing
    • Mat or shrubby
arctic tundra
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
alpine tundra
Alpine tundra
  • At high elevations at all latitudes
  • Variable daylength, many of the same restrictions, plant species
tundra animals
Tundra animals
  • Migratory, well-suited for cold climate
    • Musk oxen, caribou, reindeer
    • Lemmings, white fox, snowy owl
tropical forests
Tropical forests
  • Equatorial, mean temp. ~25°C, 12 hrs sunlight per day
  • Rainfall highly variable-determines type of tropical forest present
types of tropical forests
Types of tropical forests
  • Thorn forests - furthest from equator, prolonged dry season
types of tropical forests39
Types of tropical forests
  • Tropical deciduous forest
  • More rainfall nearer equator, distinct wet, dry seasons
  • Lose leaves during dry seasons
types of tropical forests40
Types of tropical forests
  • Tropical rain forest
  • >250 cm of rain per year
  • Perpetual midsummer conditions
  • Uninterrupted plant growth
tropical rain forests
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
tropical rain forests42
Tropical rain forests
  • Typically stratified into 5 layers
  • Each layer has characteristic plants, animals
  • May reach height of 80 m
tropical rain forest soil
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
  • 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
temperate deciduous forest
Temperate deciduous forest
  • Eastern N. Amer, N. Europe and east
  • Moderate temps., moderate moisture levels
    • 5-6-month growing season
temperate deciduous forest47
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
  • Boreal forest, coniferous forest
  • Harsh winters with lots of snow
  • 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
taiga soils
Taiga soils
  • Thin, acidic, develop slowly
  • Pine needles break down slowly in cool climate
taiga animals
Taiga animals
  • Primarily seed, insect eaters, or those that feed on plants in or near water
  • Squirrels, birds, elk, moose, deer, beaver, porcupine, grizzlies, wolves
standing freshwaters
Standing freshwaters
  • Lakes and ponds
standing freshwaters53
Standing freshwaters
  • Significant stratification in community structure
  • Light
    • Photic zone
      • Phytoplankton, zooplankton
    • Aphotic zone
      • Detritus, decomposers
moving freshwaters
Moving freshwaters
  • Longitudinal zonation in physical, chemical characteristics
  • Change in producers, benthic (bottom dwelling), fish assemblages
  • 3/4 of world’s surface, major impact on climate, wind patterns, algae supply most of world’s oxygen
  • Photic, aphotic zones (vertical)
  • Intertidal, neritic, oceanic zones (horiz.)
    • Intertidal-wetted, dried from tides
    • Neritic-shallow regions over continental shelves
    • Oceanic-beyond shelves - deep zones
  • Pelagic-open water
  • Benthic-sea floor
    • Abyssal zone-deep benthic - cold, high water pressure, no light
  • Freshwater rivers merge with oceans
  • Not very diverse - few species tolerant of salinity
  • Very productive - oysters, crabs, fish, waterfowl
  • Most in danger from water pollution