Biology 2F03: Fundamental and Applied Ecology Chapter 2: Life on ...
Biology 2F03: Fundamental and Applied Ecology Chapter 2: Life on Land 2.1 Large-Scale Patterns of Climatic Variation - Uneven heating of the earth’s spherical surface by the sun and the tilt of the earth on its axis combine to produce predictable latitudinal variation in climate - Temperature, precipitation and atmospheric circulation: Because the earth is a sphere, the sun’s rays are most concentrated where the sun is directly overhead which changes with seasons Earth’s axis is tilted approximately 23.5o away from the perpendicular June 21st during summer solstice, the sun is directly overhead at the tropic of Cancer, 23.5o N latitude December 21st during winter solstice, sun is directly overhead at tropic of Capricorn, 23.5oS latitude Sun is directly over the equator during the spring and autumnal equinoxes. On March 21st and September 23rd Heating of the earth’s surface and atmosphere drives circulation of the atmosphere and influences patterns of precipitation Air moving from 30o latitude back to the equator completes a thermal loop, which forms the Hadley cell Polar cell driven by ait movement associated with warming at 60o latitude and cooling at the poles Ferrel cells occurs at mid-latitudes, and is driven in part by the effects of the Hadley and Polar cells Prevailing winds do not move in a straight north-south direction because of the Coriolis effect - Climate diagrams: Tool to explore the relationship between the distribution of terrestrial vegetation and climate Summarize climatic information, including: seasonal variation in temperature and precipitation, length and intensity of wet and dry seasons, and the portion of the year during which average minimum temperature is above and below 0oC When the temperature line lies above the precipitation line, potential evaporation rate exceeds precipitation (dry periods) Also include mean annual temperature, precipitation and the elevation of each site above sea level 2.2 Soil: Foundations of Terrestrial Biomes - Soil structure from the long-term interaction of climate, organisms, topography, and parent mineral material - O horizons: found in soils in which the plant material is primarily aquatic in nature - LFH horizons: found in more upland sites
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Small organic horizons are found in areas with little litter decomposition or high decomposition rates Deep organic horizons are found in areas with substantial little inputs and/or low decomposition rates A horizon: contains a mixture of mineral materials (clay, silt and sand), as well as organic material derived from the organic horizon above B horizon: contains the materials leached from above, often resulting in a distinctive banding pattern C horizon: consisting of weathered parent material, broken down through the actions of frost, water, microbial activity, and deep penetrating roots Under the C horizon we fin unweathered parent material, which is often bedrock Plants secrete numerous root exudates, which along with the living roots and plant litter, serve as substrates for bacterial, fungal, and animal species Growth and activity of organisms provides stability to the mineral components of the soil, allowing development and maintenance of complex canals of air spaces and cavities within the soil Climate affects the rate of weathering parent materials, leaching of organic and inorganic substances, erosion, and decomposition of organic matter through direct weathering effects
2.3 Natural History and Geography of Biomes - The geographic distribution of terrestrial biomes correspond closely to variation in climate, especially prevailing temperature and precipitation - Tundra: Starting at the most northerly areas of vegetation, we find an open landscape of mosses, lichens, and dwarf willows, dotted with small ponds and laced with clear streams Geography: Artic tundra rings the top of the globe, covering most of the lands north of the Artic Circle Climate: Typically cold and dry Short summers Precipitation varies from less than 200mm to a little over 600mm Precipitation exceeds evaporation: summers are soggy and the tundra landscape is filled with ponds and streams Soils: Soil building is slow Rates of decomposition are low, organic matter accumulates in deposits of peat and humus Permafrost: permanently frozen layer of soil that remains frozen even during the summer months Solifluciton slowly moves soils down slopes
Freezing and thawing brings stones to the surface of the soil, forming netlike, or polygonal, pattern on the surface of tundra soils Biology: Dominated by perennial herbaceous plants: grasses, sedges, mosses, and lichens, warf willows and birches, low-growing shrubs Short periods of warm weather suitable for plant growth present significant challenges to the residents of the tundra: slow growing with nearly all of the biomass below ground, short with strong stems, continuous photosynthesis Caribou, reindeer, musk, ox, bear, wolves, artic fox, weasel, lemming, ground squirrel, ptarmigan and snowy owl Human influences: Intense exploration and extraction of oil, natural gas, and a variety of minerals such as diamonds Rapidly rising temperatures on the permafrost and rates of decomposition As permafrost melts, the rich organic material it contains becomes available to soil microbes and insects for decomposition, potentially releasing enormous amounts of CO2 Boreal forest: 11% of earth’s land area Geography: Confined to the Northern Hemisphere Climate: Winters are usually longer than 6 months, and summers are to short to support temperate forest Precipitation ranges from 200-600mm Because of low temperatures and long winters, evaporation rates are low, and drought is either infrequent or brief Soils: Low in fertility, thin, and acidic Low decomposition and low pH slow down decomposition of plant litter and the rate of soil building Biology: Evergreen conifers Steep vertical gradient in light as one moves from the top of the canopy to soil surface Strong vertical gradient in ambient temperatures as you move down through the canopy and down to the soil surface Bogs and fens dominated by moss species which have waterlogged soils with islands of vascular plants centered around a few trees and shrubs
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Migratory caribou and reindeer, moose, woodland bison, wolves, black bears, grizzly bears brown bears, lynx, wolverines, snowshoe hare, porcupines and red squirrels Human influences: Hunting and trapping impact populations of many wildlife species Cut for lumber and pulp and oil and gas exploration Temperate forest: Geography: Found between 30o and 55o latitude Climate: Temperatures are not extreme and annual precipitation averages from 650-3,000mm More winter precipitation than temperate grassland Soils: Fertile Neutral or slightly acidic pH and rich in both organic matter and inorganic nutrients Nutrient movement between soil and vegetation Biology: Temperate forest are vertically stratified Height of canopy varies from 40-100m Small arboreal mammals, deer, bear, fox, and bats Diversity of microscopic invertebrate animals Human influences: Human settlements, agriculture, harvesting of animals and plants Deciduous forests are able to recover following years of logging and agriculture Temperate grassland: Geography: Largest biome in North America and Eurasia Climate: 300-1,000mm of precipitation annually Experience droughts Maximum precipitation during the summer Soils: Derived from a variety of parent materials Deep, basic or neutral, and fertile and contain large quantities of organic matter Biology: Dominated by herbaceous vegetation Roving herbivores, steppe and prairie wolves, grizzly bear, borrowers and fleet Human influences:
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Agriculture Mediterranean woodland and shrubland: Geography: Occur on all the continents except for Antarctica Climate: Cool and moist duding fall, winter and spring while summers are hot and dry Soils: Low to moderate fertility Biology: Show adaptations to drought Trees and shrubs are typically evergreen and have small, though leaves Decomposition is slowed during summer Fire-resistant plants Animals, both vertebrate and invertebrate, are diverse Human influences: Agriculture: low-intensity cultivation and long-term sustainability Desert: Geography: Two bands of deserts ring the globe, one at about 30oN latitude and one at about 30oS latitude Climate: Environmental conditions vary from one desert to another Some receive very little rainfall and fit the stereotype of deserts as extremely dry places Some may receive nearly 300mm of rainfall annually Water loss in deserts due to evaporation and transpiration by plants exceeds precipitation during most of the year It is a lack of available water rather than extremely hot temperatures that makes a desert Soils: Generally low in organic matter, consisting primarily of sand and rock Often contain high concentrations of salts Biology: Desert landscape is sparse Plant cover is absent from many places, exposing soils and other geological features Vegetation is typically gray-green Animal abundance tends to be low but diversity can be high Human influences: Human populations in desert regions are concentrated around oases and river valleys
Many desert landscapes have been pushed until they now frow little but salt crystals Desert is one biome that because of human activity, is increasing in area Tropical savannah: Geography: Occur north and south of tropical dry forests within 10o to 20o of the equator Climate: Life on the savannah cycles to the rhythms of altering dry and wet seasons Fires help maintain the tropical savannah as a landscape of grassland and scattered trees Lightning storms Longer dry season and lower annual precipitation Mean rainfall between 300-500mm Soils: Soil layers with permeability to water play a key role in maintaining many tropical savannas Biology: Populated by wandering animals that move in response to seasonal and year-to-year variations in rainfall and food availability Parklike landscape of the savannah is maintained by a dynamic interplay of physical and biological forces Human influences: Fire Hunting and gathering Pastoralism Live stock ranching Tropical dry forest: Geography: Between about 10o and 25o of latitude Climate: More seasonal than that of tropical rain forests Dry season lasting for six to seven months, followed by a season of abundant rainfall Heavy rains occur during the wet season with precipitation similar to that found in tropical rain forest Soils: Of great age Less acidic than those of rain forests and are richer in nutrients Highly vulnerable to erosion Biology: Plants are strongly influenced by physical factors
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Share many animal species with the rain forest and savannah Human influences: Heavy human settlement has devastated the tropical dry forest Tropical dry forests have nearly disappeared Agricultural development Tropical rain forest: Geography: Straddle the equator in three major regions: Southeast Asia, West Africa, and South Central America Occur within 10o of; attitude north or south of the equator Climate: Conditions are warm and wet year-round Least seasonal on earth Soils: Organic horizon is narrow Nutrient-poor, acidic, thin, and low in organic matter Lateritic soils: result of extensive weathering of the parent rocks, resulting in high concentrations of iron and aluminum, and low concentrations of essential plant nutrients Rain forest plants are adept at conserving and acquiring nutrients Biology: Trees dominate the rain forest landscape Buttress roots provide structural support Shallow roots Insects are the most diverse Human influences: Many of the world’s staple foods and prescription drugs derive from tropical plants Humans have exploited tropical rainforest through hunting and gathering and shifting agriculture Destroying rain forest for timber, minerals, and short-lived agricultural profits Mountains – islands in the sky: Geography: Mountains are built by geological processes Mountains are concentrated in belts where these geological forces have been at work Climate: Climates change from low to high elevation, but the specific changes are different at different latitudes Soils: Changes with elevation and have a great deal in common with the various soils of each separate biome
Because of the steeper topography, mountain soils are generally well drained and tend to be thin and vulnerable to erosion Persistent winds blowing from the lowlands deposit soil particles and organic matter on mountains Biology: Changes with elevation Human influences: Useful as a source of raw materials such as wood, forage for animals, medicinal plants, and minerals Human exploitation has produced ecological degradation in many places and balance in others
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Small organic horizons are found in areas with little litter decomposition or high decomposition rates Deep organic horizons are found in areas with substantial little inputs and/or low decomposition rates A horizon: contains a mixture of mineral materials (clay, silt and sand), as well as organic material derived from the organic horizon above B horizon: contains the materials leached from above, often resulting in a distinctive banding pattern C horizon: consisting of weathered parent material, broken down through the actions of frost, water, microbial activity, and deep penetrating roots Under the C horizon we fin unweathered parent material, which is often bedrock Plants secrete numerous root exudates, which along with the living roots and plant litter, serve as substrates for bacterial, fungal, and animal species Growth and activity of organisms provides stability to the mineral components of the soil, allowing development and maintenance of complex canals of air spaces and cavities within the soil Climate affects the rate of weathering parent materials, leaching of organic and inorganic substances, erosion, and decomposition of organic matter through direct weathering effects
2.3 Natural History and Geography of Biomes - The geographic distribution of terrestrial biomes correspond closely to variation in climate, especially prevailing temperature and precipitation - Tundra: Starting at the most northerly areas of vegetation, we find an open landscape of mosses, lichens, and dwarf willows, dotted with small ponds and laced with clear streams Geography: Artic tundra rings the top of the globe, covering most of the lands north of the Artic Circle Climate: Typically cold and dry Short summers Precipitation varies from less than 200mm to a little over 600mm Precipitation exceeds evaporation: summers are soggy and the tundra landscape is filled with ponds and streams Soils: Soil building is slow Rates of decomposition are low, organic matter accumulates in deposits of peat and humus Permafrost: permanently frozen layer of soil that remains frozen even during the summer months Solifluciton slowly moves soils down slopes
Freezing and thawing brings stones to the surface of the soil, forming netlike, or polygonal, pattern on the surface of tundra soils Biology: Dominated by perennial herbaceous plants: grasses, sedges, mosses, and lichens, warf willows and birches, low-growing shrubs Short periods of warm weather suitable for plant growth present significant challenges to the residents of the tundra: slow growing with nearly all of the biomass below ground, short with strong stems, continuous photosynthesis Caribou, reindeer, musk, ox, bear, wolves, artic fox, weasel, lemming, ground squirrel, ptarmigan and snowy owl Human influences: Intense exploration and extraction of oil, natural gas, and a variety of minerals such as diamonds Rapidly rising temperatures on the permafrost and rates of decomposition As permafrost melts, the rich organic material it contains becomes available to soil microbes and insects for decomposition, potentially releasing enormous amounts of CO2 Boreal forest: 11% of earth’s land area Geography: Confined to the Northern Hemisphere Climate: Winters are usually longer than 6 months, and summers are to short to support temperate forest Precipitation ranges from 200-600mm Because of low temperatures and long winters, evaporation rates are low, and drought is either infrequent or brief Soils: Low in fertility, thin, and acidic Low decomposition and low pH slow down decomposition of plant litter and the rate of soil building Biology: Evergreen conifers Steep vertical gradient in light as one moves from the top of the canopy to soil surface Strong vertical gradient in ambient temperatures as you move down through the canopy and down to the soil surface Bogs and fens dominated by moss species which have waterlogged soils with islands of vascular plants centered around a few trees and shrubs
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Migratory caribou and reindeer, moose, woodland bison, wolves, black bears, grizzly bears brown bears, lynx, wolverines, snowshoe hare, porcupines and red squirrels Human influences: Hunting and trapping impact populations of many wildlife species Cut for lumber and pulp and oil and gas exploration Temperate forest: Geography: Found between 30o and 55o latitude Climate: Temperatures are not extreme and annual precipitation averages from 650-3,000mm More winter precipitation than temperate grassland Soils: Fertile Neutral or slightly acidic pH and rich in both organic matter and inorganic nutrients Nutrient movement between soil and vegetation Biology: Temperate forest are vertically stratified Height of canopy varies from 40-100m Small arboreal mammals, deer, bear, fox, and bats Diversity of microscopic invertebrate animals Human influences: Human settlements, agriculture, harvesting of animals and plants Deciduous forests are able to recover following years of logging and agriculture Temperate grassland: Geography: Largest biome in North America and Eurasia Climate: 300-1,000mm of precipitation annually Experience droughts Maximum precipitation during the summer Soils: Derived from a variety of parent materials Deep, basic or neutral, and fertile and contain large quantities of organic matter Biology: Dominated by herbaceous vegetation Roving herbivores, steppe and prairie wolves, grizzly bear, borrowers and fleet Human influences:
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Agriculture Mediterranean woodland and shrubland: Geography: Occur on all the continents except for Antarctica Climate: Cool and moist duding fall, winter and spring while summers are hot and dry Soils: Low to moderate fertility Biology: Show adaptations to drought Trees and shrubs are typically evergreen and have small, though leaves Decomposition is slowed during summer Fire-resistant plants Animals, both vertebrate and invertebrate, are diverse Human influences: Agriculture: low-intensity cultivation and long-term sustainability Desert: Geography: Two bands of deserts ring the globe, one at about 30oN latitude and one at about 30oS latitude Climate: Environmental conditions vary from one desert to another Some receive very little rainfall and fit the stereotype of deserts as extremely dry places Some may receive nearly 300mm of rainfall annually Water loss in deserts due to evaporation and transpiration by plants exceeds precipitation during most of the year It is a lack of available water rather than extremely hot temperatures that makes a desert Soils: Generally low in organic matter, consisting primarily of sand and rock Often contain high concentrations of salts Biology: Desert landscape is sparse Plant cover is absent from many places, exposing soils and other geological features Vegetation is typically gray-green Animal abundance tends to be low but diversity can be high Human influences: Human populations in desert regions are concentrated around oases and river valleys
Many desert landscapes have been pushed until they now frow little but salt crystals Desert is one biome that because of human activity, is increasing in area Tropical savannah: Geography: Occur north and south of tropical dry forests within 10o to 20o of the equator Climate: Life on the savannah cycles to the rhythms of altering dry and wet seasons Fires help maintain the tropical savannah as a landscape of grassland and scattered trees Lightning storms Longer dry season and lower annual precipitation Mean rainfall between 300-500mm Soils: Soil layers with permeability to water play a key role in maintaining many tropical savannas Biology: Populated by wandering animals that move in response to seasonal and year-to-year variations in rainfall and food availability Parklike landscape of the savannah is maintained by a dynamic interplay of physical and biological forces Human influences: Fire Hunting and gathering Pastoralism Live stock ranching Tropical dry forest: Geography: Between about 10o and 25o of latitude Climate: More seasonal than that of tropical rain forests Dry season lasting for six to seven months, followed by a season of abundant rainfall Heavy rains occur during the wet season with precipitation similar to that found in tropical rain forest Soils: Of great age Less acidic than those of rain forests and are richer in nutrients Highly vulnerable to erosion Biology: Plants are strongly influenced by physical factors
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Share many animal species with the rain forest and savannah Human influences: Heavy human settlement has devastated the tropical dry forest Tropical dry forests have nearly disappeared Agricultural development Tropical rain forest: Geography: Straddle the equator in three major regions: Southeast Asia, West Africa, and South Central America Occur within 10o of; attitude north or south of the equator Climate: Conditions are warm and wet year-round Least seasonal on earth Soils: Organic horizon is narrow Nutrient-poor, acidic, thin, and low in organic matter Lateritic soils: result of extensive weathering of the parent rocks, resulting in high concentrations of iron and aluminum, and low concentrations of essential plant nutrients Rain forest plants are adept at conserving and acquiring nutrients Biology: Trees dominate the rain forest landscape Buttress roots provide structural support Shallow roots Insects are the most diverse Human influences: Many of the world’s staple foods and prescription drugs derive from tropical plants Humans have exploited tropical rainforest through hunting and gathering and shifting agriculture Destroying rain forest for timber, minerals, and short-lived agricultural profits Mountains – islands in the sky: Geography: Mountains are built by geological processes Mountains are concentrated in belts where these geological forces have been at work Climate: Climates change from low to high elevation, but the specific changes are different at different latitudes Soils: Changes with elevation and have a great deal in common with the various soils of each separate biome
Because of the steeper topography, mountain soils are generally well drained and tend to be thin and vulnerable to erosion Persistent winds blowing from the lowlands deposit soil particles and organic matter on mountains Biology: Changes with elevation Human influences: Useful as a source of raw materials such as wood, forage for animals, medicinal plants, and minerals Human exploitation has produced ecological degradation in many places and balance in others
