Ch. 5: Biomes: Global Patterns of Life What is the use of a house if you havent got a tolerable planet to put it on? ~ Henry David Thoreau 1 Learning Outcomes You should be able to 1. Recognize the characteristics of some major terrestrial biomes. 2. Understand how and why marine environments vary with depth and distance from shore. 3. Compare the characteristics and biological importance of major freshwater ecosystems.
4. Summarize the overall patterns of human disturbance of world biomes. 2 Terrestrial Biomes Biomes - areas sharing similar climate, topographic and soil conditions, and thus the same basic types of biological communities. Determined by temperature and
precipitation 3 Biomes 4 Biomes Temperature and precipitation also change with altitude. As you go up a mountain, it gets cooler and wetter.
Vertical zonation is a term applied to vegetation zones defined by altitude. 5 Minnesota Biomes 6 Tropical Rainforests moist, rain year-round Humid regions in the tropics that support one of the most complex and biologically rich biomes.
Environmental Links: Soil in rainforests tends to be thin, acidic and nutrient poor. 90% nutrients tied up in living organisms Rapid decomposition and nutrient cycling The soil cannot support continued cropping and cannot resist erosion from frequent rains. Rapid deforestation occurring as people move into the forests
One half to two thirds of all the species of terrestrial plants and animals live in tropical forests. 7 Tropical Seasonal Forests have yearly dry seasons Many tropical regions are characterized by wet and dry seasons with hot temperatures year round. Environmental Links: Few of the tropical seasonal forests remain in their natural state as humans use fire to clear the land in the dry season and settle there. Soil is richer than rainforest, therefore more
productive land for agriculture. 8 Tropical Savannas and Grasslands support few trees Grasslands with sparse tree cover, which we call savannas. Environmental Links: Small rainfall amounts do not support forests Dry season prone to fire Plants with deep, long-lived
roots and other adaptations to survive drought, heat, and fire Many migratory grazers such as antelope, wildebeest, or bison 9 Deserts hot or cold, all are dry Characterized by low moisture levels (less than 30 cm per year) and precipitation that is infrequent and unpredictable from year to year. Plant and animal adaptations to conserve water
Environmental Links Slow growing vegetation is damaged by off road vehicles. It takes decades for desert soils to recover. Overgrazing - Livestock are destroying the plants of the southern Sahara. Without plants the land cannot retain what little rainfall there is and it becomes more barren. 10
Temperate Grasslands rich soils Communities of grasses and seasonal herbaceous flowering plants Environmental Links Few trees due to inadequate rainfall Large daily and seasonal temperature fluctuations Thick organic soils
Much converted to farmland. Tallgrass prairies in the U.S. are now mostly farms. Overgrazing is a threat because it kills the plants and permits erosion to occur. 11 Temperate Shrubland (Mediterranean) Characterized by warm, dry summers and cool, moist winters Environmental Links: Fires are a major factor in plant succession. Referred to as chaparral in California
- High number of unique species - Human homes built in chaparral harm endangered wildlife and burn periodically. - Also found along Mediterranean coast, southwestern Australia, central Chile and South Africa 12 Temperate Forests Temperate regions support lush summer plant growth when water is plentiful. Can be deciduous (loses leaves seasonally) or coniferous (conebearing; also called temperate rainforests)
Environmental Links: Eastern half of U.S. was covered with broad leaf deciduous forest. Much of that was harvested for timber. Areas in U.S. have re-grown, although the dominant species are different Areas in Siberia severely threatened now, may be region with greatest rate of deforestation in the world today 13 Boreal Forests occur at high latitudes
Boreal Forest - Broad band of mixed coniferous and deciduous trees. Dominated by pines, hemlock, spruce, cedar and fir with some deciduous trees mixed in. Taiga - Northernmost edge of boreal forest Extreme cold and short summers limit the growth rate of trees. 14 Tundra Treeless landscape
Temps below freezing most of the year Small, hardy vegetation Low plant diversity, frost can occur even in the summer Occurs at high latitudes or on mountaintops. 15 Marine Ecosystems Oceans cover 3/4 of Earths surface. Photosynthesis is carried out by algae or free floating plants
(phytoplankton). Greatest amount of photosynthesis near the coast where nutrients wash in. Organisms die and fall to sea floor where the nutrients are used in deep ocean ecosystems. Upwelling currents circulate nutrients from the ocean floor back to the surface. Satellite measurements of chlorophyll levels in the oceans and on land. Light green and yellow oceans zones are biologically rich.
16 Zones of the Ocean Vertical stratification is a key feature: light and temp decrease with depth Cold water holds more oxygen than warm, so more productivity Ocean systems classified by depth and location to shore: Benthic - bottom Pelagic - water column
above the bottom Area near shore is known as littoral zone 17 Surface to Hadal Zone Communities Open ocean is a biological desert except for areas where nutrients are distributed by currents The deepest layer of the ocean (hadal zone) contains communities of tube worms, mussels, etc. supported by microbes that capture chemical
energy from thermal vents on the ocean floor. These organisms are adapted to extreme temperatures (350oC) and intense pressure. 18 Coastal Zones Support rich, diverse communities Communities vary with depth, light, temperature and nutrient concentration. Coral Reefs - Aggregations of coral polyps that live symbiotically with algae. Their calcium rich skeletons build up the reef.
Environmental Links: Threatened by trash, sewage, urban runoff, industrial waste, introduced pathogens and global warming. Global warming causes coral bleaching in which corals expel their algal partners and then die. One third of coral reefs have already been destroyed and 60% of the remaining reefs will probably be dead by 2030. Economically important due to tourism. 19 Mangroves Mangroves are trees that grow in saltwater along tropical coastlines. Environmental Links: Help stabilize shoreline
Nurseries for fish, shrimp Can be cut for timber 20 Tidal Environments Estuaries - bays or semi-enclosed bodies of brackish water that form where rivers enter the ocean Salt marshes - coastal wetlands flooded regularly or occasionally by seawater Environmental Links: Both are nutrient rich and biologically diverse. 2/3 of marine fish and shellfish rely
on estuaries for spawning and development. Threatened by sewage from coastal cities 21 Tide Pools Depressions in a rocky shoreline that are flooded at high tide but retain some water at low tide Wave action prevents most plant growth, but animals can be found in tidal pools. Diverse specialized species adapted to the harsh conditions. 22
Barrier Islands Narrow islands made of sand that form parallel to a coastline Provide protection from storms, waves, tides Since they are made of sand, they should not be built on, but they are. Oftentimes, storms destroy the buildings. About 20% in the US have been developed. 23 Freshwater Ecosystems Lakes Freshwater lakes have distinct vertical zones. Epilimnion - warm upper layer Hypolimnion - cold, deeper layer that does not mix Thermocline distinctive
temperature transition zone that separates warm upper layer and deeper cold layer Benthos - bottom 24 Wetlands Shallow and productive Land surface is saturated or covered with water at least part of the year. Swamps (with trees) and Marshes (without trees) high productivity
Bogs and Fens waterlogged soils that tend to accumulate peat. Bogs fed by precipitation, while fens are fed from groundwater. Nutrient poor with low productivity, but many unusual species Environmental Links: Conservation is very important due to rich biodiversity. Wetlands are the breeding grounds for birds. One of the greatest areas of concern for biologists. May gradually convert to terrestrial communities through succession 25
Human Disturbance By some estimates, humans preempt about 40% of net terrestrial primary productivity. Conversion of habitat to human use is single largest cause of biodiversity loss. Temperate deciduous forests are the most completely human-dominated biome. Tundra and Arctic Deserts are the least disturbed. About half of all original wetlands in the U.S. have been degraded over the past 250 years. 26 Human Disturbance
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