Large Land Vegetation Types
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
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
Pampas
Veldt
Tropical:
Savanna
Figure 6.19a
Figure 6.23a
Chaparral or Mediterranean
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
Conifer Forests
Southern Pine Forests
Long warm growing season
Commercial forests
Boreal Forests: northern hemisphere only
45°to 60°north
Pines, hemlocks, spruce, cedar, fir
Conifer Forests
Taiga
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
Permafrost restricts water movement and root growth
Short growing season—50 days
Figure 6.25a
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
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
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
Estuaries
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
BarrierIslands
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
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
Overabundance of nutrients—algal blooms, as algae die, dissolved O2 consumed by decomposition, not enough O2 for other organisms
Fresh Water
Oligotrophic lakes—nutrient poor
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