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Biomes
 Large land vegetation types
 Climate or average weather conditions, profoundly influences life, producing distinctive
vegetation types in various parts of world
 Distribution of grasslands, rain forest, tundra mainly influenced by prevailing temperature and
rainfall
Figure 6.16
Figure 6.17
Deserts
Receive less than 25 cm of sporadic rainfall per year
Hot deserts—Sahara
Temperate—Mojave
Cold—Atacama in Chile
Deserts
 Plants and animals adapted to water conservation
 Plants may get water from fog, thick epidermis, fuzz
 Animals may never drink, get water from food, nocturnal
 Major deserts found along 30° north and south due to air circulation
Deserts
 Large interior area of land masses away from oceans
 Rain shadow
 Fragile
 Desertification—due to overgrazing and loss of topsoil
Figure 6.24a
Grasslands
 Dry, sometimes produce large biomass
 25-100 cm of rainfall/year
 Extremes in temperature
 Tall grass prairie—converted to cropland in North America: 90%
 Mixed grass
 Short grass: high plains closer to Rockies
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Grassland
 Erosion—loss of topsoil resulting from overfarming—no cover crops and excessive grazing of
even the deep roots
Grasslands
Adapted to extremes in temperature
Seasonality of precipitation types—snow in winter, rain in summer
Deep rooted grasses
Accumulation of dead plants produces thick, organic topsoils
May be fire adapted
Grasslands
 Temperate:
 Prairies
 Steppes
 P a m pa s
 Veldt
 Tropical:
 Savanna
Figure 6.19a
Figure 6.23a
Chaparral or Mediterranean
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Cool rainy winters, hot dry summers
Evergreen funky-looking shrubs, occasional pines and scrub oaks, grasses
Small, leathery leaves
Rodents, reptiles, birds
Fire adapted
Chaparral
 Drier areas—sagebrush scrub
 Great basin in North America
 Sahel (border of Sahara)—thornbush scrub
Figure 6.27a
Temperate Deciduous Forests
 Deciduous—lose leaves
 Temperate—midlatitude, cold in winter, warm in summer
 75-200 cm rain/yr
 Great Lakes to eastern seaboard of US, south to Gulf of Mexico
 Original vegetation of most of Europe and eastern Canada
Temperate Forests
 Maple, oak and beech are common trees
 Woody and herbaceous understory
 Wide variety of animals
 Massive habitat destruction wherever it occurs
Figure 6.18a
Conifer Forests
 Cone bearing trees in temperate areas, but with sandy soils (nutrient and water poor)
 Leaves are waxy needles of varying length to prevent extensive water loss
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 Southern Pine Forests
Conifer Forests
 Long warm growing season
 Commercial forests
 Boreal Forests: northern hemisphere only
 45° to 60° north
 Pines, hemlocks, spruce, cedar, fir
 Taiga
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Conifer Forests
Edge of boreal
Forest gives rise to tundra
Dry, cold, short growing season
Figure 6.26a
Temperate Rainforest
Heavy rainfall
Fertile soils
Objects of contention over land use
Olympic National Forest and Seashore
Figure 6.20a
Tundra
 Cold, low-lying area of north
 Low-growing shrubs, mosses, lichens, sedges
 25 cm rain
 Marshy areas, shallow lakes
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 Permafrost restricts water movement and root growth
 Short growing season—50 days
Figure 6.25a
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Tropical Rain Forests
220-450 cm rain/year
Hot all year
Lush vegetation (high productivity)
Poor soils—rapid decomposition prevents soil from building up
Biogeochemical cycle—heavy on the bio
Amazon basin, Central America, equatorial Africa, parts of Southeast Asia
Tropical Rainforest
Lock up tremendous amounts of carbon in vegetation—carbon sink
Enormous species diversity (300 species in one hectare)
Potential source of medicine and other commercial products
Plants and animals –biocentric conservation
Figure 6.21a
Tropical Dry Forests
 Wet and dry seasons
 Hot all year
 Tropical evergreen or partly deciduous forest with
 Open woodland and grassy savannas
 Better soils
 Heavily exploited
Aquatic Systems
 Marine
 Ocean
 Coral reefs
 Tidal wetlands
 Barrier islands
 Freshwater
 Lakes
 wetlands
Oceans
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Coastal zone from high tide mark to point where continental self drops off
Intertidal zone—between high and low tide
Open ocean extends out from coastal zone
Pelagic—vertical distance from ocean surface to ocean floor
Benthic zone—ocean floor
Photic zone—to 100 m below surface
Figure 16.8
Oceans
 Productivity –highest near coast, low in open ocean
 Coastal zone productive—waves bring in nutrients, carry away waste, exposure to sun
Oceans: coastal areas
 10% of ocean area, 90% of species
 Great fisheries
 75% of Earth’s surface
Figure 16.6
Oceans
 Open oceans-- less productivity than deserts
 Open oceans—nutrient poor
 Most productive near poles, rich in phyto and zooplankton
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Coral Reefs
Shallow tropical oceans
Limestone deposits from generations of coral polyps
Coral-polyps—animals and algae
Biodiversity—great
 2% ocean floor
 25% ocean species
Coral Reefs
In peril
Bleached coral reefs
Algae die, then rest of polyp
Ocean warming, ozone depletion, pollution
Coral reef watch
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Where river flows into ocean
Mix of salt and freshwater
High nutrient load
Supports all stages of life
Buffer between ocean and land
Sponge—capable of absorbing water
Prevent surges from ocean
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narrow sandy islands
Continental shelf is shallow
Protect lagoons and salt marshes from storm damage
Vacation homes upset sand deposition
Fresh Water Systems
Cover only 2.1% of earth’s surface
Lakes, rivers, other water
Littoral zone—shallow water along edge, plants can root
Limnetic--vertical zone—vertical region from surface to point that light can deliver light for
photosynthesis
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Estuaries
Barrier Islands
Fresh Water Systems
 Profundal zone—deepest layers, light can’t penetrate
 Thermocline—temperature drop off
Fresh Water systems
 Eutrophic lakes—nutrient rich
 Artificial—human activities: fertilizer runoff, sewage, detergents, bedrock disturbance
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Overabundance of nutrients—algal blooms, as algae die, dissolved O2 consumed by
decomposition, not enough O2 for other organisms
 Oligotrophic lakes—nutrient poor
Fresh Water
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Wetlands
Inundated with water at least part of year
Swamps, bogs, tidal marshes
High biological productivity
Habitat for migratory birds
Reduced by 55% since arrival of Europeans in US
Wetlands
Big push for conservation or reclamation
Swamps—wetlands with trees
Marshes—no trees
Bogs—saturated ground
Fens—fed by groundwater