Biogeography Climate, Biomes, and Terrestrial Biodiversity

Transcription

1 Biogeography Climate, Biomes, and Terrestrial Biodiversity

2 6-1 Weather and Climate

3 What is Weather? Definition: the short-term properties of the troposphere at a particular place and time Properties: 1. Temperature 2. Pressure 3. Humidity 4. Precipitation 5. Sunshine 6. Cloud cover 7. Wind direction and speed

4 Why is Weather so changeable? Weather changes as one air mass replaces or meets another, and this happens constantly, because of the variety of air masses Air masses are: Wet or dry Hot or cold Have high or low pressures Most dramatic weather occur along a Warm front: an advancing warm air mass and the cooler one is replacing it. Warm is less dense so it rises and the moisture condenses into different altitudes. HI & DRY Cold Front: advancing mass of cold air. Cold air more dense than warm so it stays close to the ground. WET & LOW

5 Air Mass

6 What is Climate? Definition: a region s general pattern of atmospheric or weather conditions, including variations and weather extremes over a log period of time Two main factors determining a regions climate: Average temperature Average precipitation

7 How does global air circulation affect regional climates? It affects the rainfall, the temperatures of different regions, and affects air and water properties Factors that determine global air circulation patterns: 1. Uneven heating of the earth s surface: heated more at the equator so hotter at the equator than at poles 2. Seasonal changes in temperature and precipitation because of tilted axis. 3. Rotation of the earth on its axis. Creates six convection cells. Northern hemisphere air masses rotate to the right. Southern Hemisphere air masses move to the left. 4. Long-term variations in the amount of solar energy striking the earth 5. Properties of air and water

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9 How do ocean currents effect regional climates? Have the same factors as air plus differences in water density The currents are driven by winds and the earth s rotation redistribute heat from the sun and influences climate and vegetation. Warm and cold currents affect whether the air pressure would be high or low The gulf stream warms northwestern Europe, with out it it would be sub arctic Warm currents moving from the equator warms Japan and Alaska Upwellings of cold nutrient-rich bottom water replace outgoing surface water being pushed by trade winds blowing offshore. Bring nutrients to the surface and support large populations of phytoplankton, zooplankton, fish, and fish-eating sea-birds

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11 What is the El Nino- Southern Oscillation? the prevailing westerly winds weaken or cease, and surface water along the South and North American coasts becomes warmer Surface water along South and North American coasts becomes warmer Upwelling is suppressed and it lowers primary productivity and a decline in fish species Extreme weather conditions in lands along pacific and Indian Ocean Produces a mild winter in the Northern & mid-western states, blocked hurricanes on Atlantic coast

12 What is La Nina? The cooling effects opposite to El Nino Torrential rains in Southeast Asia More Atlantic Ocean Hurricanes Colder winters in Canada and Northeast Warmer and drier winters in the southeastern and Southwestern U.S. Wetter winter in the pacific Northwest Lower wheat yields in Argentina More wildfires in Florida

13 How does the chemical Makeup of the atmosphere lead to the Greenhouse effect? 6 greenhouse gases play a key role: Water vapor (primary greenhouse gas), carbon dioxide, ozone, methane, nitrous oxide, and chlorofluorocarbons Chemical makeup of the atmosphere leads to the Greenhouse effect by allowing heat in Protect from UV rays Trap some heat to keep the world sustainable Without earth s naturally occurring greenhouse gases, the earth would have an average surface temperature of 0 degrees F (-18 degrees C).

14 Greenhouse gasses absorbs some of the heat molecules and emitted into the troposphere as infrared radiation, which warms the air

15 How does the chemical makeup of the atmosphere create the ozone layer? In a band of the stratosphere kilometers above the earth s surface, oxygen (O2) is continuously converted to ozone (O3) and back to oxygen by a sequence of reactions initiated by UV radiation from the sun. The result is a thin veil of protective ozone at very low concentrations. 3O2 + UV à 2O3 There are 3 bands in the stratosphere A,B, & C. 1. The ozone blocks out nearly all the high-energy and shortest wavelength UV-C 2. Approximately ½ of the next highest ban UV-B 3. A small part of the lowest-energy radiation UV-A

16 How do topography and other features of the earth s surface create microclimates? Mountains interrupt the flow of prevailing surface winds and the movement of storms Microclimate: create local climatic conditions that differ from the general region Rainshadow effect: High elevation of topography prevents rain from passing mountaintops to go to other side of landmass

17 Rainshadow effect Moist air blowing from the ocean reaches a mountain range, it cools as it rises The air loses moisture as rain & snow on the windward slopes The drier air mass flows down the leeward slopes, it takes the moisture out of the plants and soil creating a semiarid or arid conditions

18 6-2 Biomes: Climate

19 Why are there different organisms in different places? Different climates caused mostly by differences in average temperature and precipitation caused by global air circulation. Different climates can sustain different communities of organisms. Climate and vegetation vary with altitude (elevation above sea level) and latitude (distance from equator). The farther away from the equator and sea level you go the colder it gets and thus the vegetation changes as well There are no set boundaries between biomes rather there are transitional zones called ecotones. Also the number of plants in each biome vary from one location to another because of small variations in climate, soil types, and natural and human caused disturbances Precipitation is a limiting factor that determines whether a land area is a desert, grassland, or forest

20 Why do plant sizes, shapes, and survival strategies differ? Succulent Plants: survive in dry climates by having a vertical orientation of most surfaces, no leaves and the ability to store water and synthesize food in their expandable, fleshy tissue. The shape of the plant and lack of leaves give it less surface area away from the sun for radiating heat out, some open their pores to take up carbon dioxide only at night Broadleaf Evergreen: trees of wet tropical rain forests which keeps most of their broad, leaves year-round. Large surface area allows them it collect ample sunlight for photosynthesis and radiate heat during hot weather Broadleaf Deciduous: survives drought and cold by shedding their leaves and becoming dormant during droughts and severe cold Coniferous: Cone bearing plants. They keep some of their narrow, pointed leaves all year. The waxy coating, shape, and clustering of needles slow down heat loss and evaporation during the long cold winters.

21 6-3 Desert Biomes Desert: An area where evaporation exceeds precipitation There are four major types: Tropical deserts Temperate deserts Cold deserts Semidesert Location: They cover about 30% of the earth s land, and are situated mainly between tropical and subtropical regions north & south of the equator at 30 degrees latitude north and south. The largest deserts are found in the interiors of continents far from moist sea air. Others can be found on the downwind sides of mountain ranges because of the rain shadow effect

22 Tropical deserts Ex: Southern Sahara in Africa Temperature usually high year-round and there is little rain (falls only 1-2 months out of the year) Few plants and a hard, windblown surface strewn with rocks and some sand

23 Temperate desert Ex: Mojave, South California Climate: daytime temperatures are high in summer and low in winter, and there is more precipitation than in tropical deserts. Flora: Sparse vegetation, widely dispersed, drought resistant shrubs and cacti or other succulents. Fauna: Animals are adapted to the lack of water and temperature variations

24 Cold desert Ex: Gobi desert, China Climate: Winters are cold, summers are warm or hot, and precipitation is low

25 Semi desert Location: found between grasslands and deserts Plants: dominated by thorn trees and shrubs adapted to long dry spells followed by brief heavy rains

26 How do desert plants survive? Evergreens with wax-coated leaves the minimize transpiration Small leaves or no leaves (cacti) which helps conserve water Many are annual wildflowers and grasses that store much of their biomass in seeds during dry periods and remain inactive until they get enough water to germinate Some succulent plants have spines to prevent herbivore consumption Some secret toxins into the soil

27 How do desert animals survive? Most are small; beat the heat and reduce water loss by evaporative cooling Hide in crevices or holes in the ground during the day and only come out at night Birds and other seed eating species feed on the deserts annual plants The larger carnivores only come out at night to prey on the rodent species Some animals have special ways to conserve water Insects get water from the food they eat Some animals are dormant during extreme neat or drought periods and come out only when it is

28 How human activities impact desert ecosystem Disruption and pollution of extracting oil, minerals, and building materials ( road stone & sand) Irrigation of some deserts areas to grow crops: Salinization from salt build up Depletion of underground water aquifers as desert cities expand Rapid growth of large desert cities: people destroying fragile desert soil, plants, and animal burrows with four-wheel drive vehicles, motorcycles, and urban development Use of remote desert areas to store Toxic radioactive waste Underground testing of nuclear weapons Maneuvers by heavy tanks and other military vehicles

29 6-4 Grassland, tundra, & Chaparral Biomes

30 Grasslands Grasslands: regions with enough average annual precipitation to allow grass (and few trees) to prosper but with precipitation so erratic that drought and fire prevent large stands of trees from growing. Major types: Tropical Grasslands Temperate Grasslands Polar Grasslands Characteristics: 1) Seasonal drought 2) Grazing by large herbivores 3) Periodic fires, all of which keep large numbers of shrubs and trees from invading and becoming established

31 Tropical Savannas Location: Occur in a wild belt on either side of the equator beyond the borders of tropical rain forests Climate: High avg. temperature year round. 2 prolonged dry seasons. Abundant rain the rest of the year Flora: consists of grasslands w/ stands of deciduous shrubs & trees; shed leaves during dry season to reduce water loss. Ex: Acacia, Eucalyptus Fauna: Enormous herd of grazing & browsing hoofed animals:wildebeests, gazelles, zebras, giraffes, antelopes. Predators: lions, tigers, cheetahs, hyenas, eagles, hawks. Large Animals: elephants, rhinoceroses

32 Temperate Grasslands Location: cover vast expanses of plains & gently rolling hills in the interiors of North and South America, Europe, Asia Climate: Seasonal extremes of hot and cold. Winters: bitterly cold. Summers: hot &dry. Annual precipitation: cm unevenly throughout the year. Prone to fires Types of temperate grasslands: Tall grass prairies and short grass prairies of the mid-west US South American Pampas African veldt Steppes of central Europe and Asia

33 Temperate grasslands Flora: Grassland plants have evolved the ability to grow back rapidly after a fire Soil: Rich nutrients because of constant decomposition. Widely used to grow crops

34 Polar Grasslands aka Arctic Tundra Location: occur South or arctic polar ice cap. Covers 10% of earth s land area Flora: carpeted with a thick spongy mat of low growing plants primarily grasses, mosses, and dwarf, woody shrubs Climate: These treeless plains are bitterly cold, swept frigid winds, and covered with ice and snow. Winters: long and dark, scant precipitation falls mostly as snow Adapted to: 1. Lack of sunlight 2. Freezing temperatures 3. Constant high winds

35 Alpine Tundra another type of tundra Location: occurs above the limit of tree growth but below the permanent snow line on high mountains Fauna: elk, mountain goats, sheep, golden eagles, marmots, ground squirrels Flora: vegetation similar to arctic tundra; gets more sunlight than arctic vegetation so there is no permafrost layer. In the summer for a few weeks the wildflowers bloom

36 Impact of human activities on grassland ecosystems Burning, plowing up, and converting some areas of savanna into cropland: release large quantities of CO2 into atmosphere à contribute to greenhouse effect Overgrazing by livestock: desertification Plowing large areas of fertile temperate grasslands into highly productive cropland: can keep producing much of the worlds cereal grains. Poor farming practices can lead to severe erosion and loss of topsoil à desertification Damaging fragile arctic tundra in Alaska & Siberia: caused by oil exploration and drilling à air pollution, spills or leaks of oil and toxic wastes, and disruption of soil and vegetation by vehicles

37 Chaparral Spanish for thicket Climate: warm, dry summers and cool, moist winters. Flora: Evergreen shrubs with small leathery leaves form dense thickets. Scrub oaks, drought-resistant pines, or other small trees often cluster in sheltered valleys Contains a high number of unique species and is often considered a hot spot for biodiversity Fires burn fiercely in the fuel-rich plant assemblages and are a major factor in plant succession. Annual spring flower often bloom profusely, especially after fires

38 6-5 Forest Biomes Undisturbed areas with moderate to high average annual precipitation, that contains various species of trees and smaller forms of vegetation Major types: Tropical Temperate Boreal (polar)

39 Tropical Rainforest Type of broadleaf evergreen forest Location: near equator. Largest found in South America Amazon River basin Climate: hot moist air. Warm annual mean temperature, high humidity, heavy rainfall almost daily. Little wind because of dense vegetation Habitats for 50-80% of the earth s terrestrial species Cover 2% of earth s land Soil: little surface litter on ground. Decomposition is quick because of warm, moist conditions and hordes of decomposers Most minerals are released by decomposition are taken up quickly by plants. Most nutrients are stored in biomass of living organisms Fauna: many plants evolved ways to survive; some use huge dark green leaves to capture sunlight, some can climb on other plants (vines), some attach themselves to the trunks of trees and branches, large trees have shallow roots

40 Tropical Deciduous Forest Aka tropica; monsoon forests or tropical seasonal forests Climate: warm year round, most of the plentiful rainfall during a wet (monsoon) season that is followed by a long dry season Lower canopy than tropical rainforests Flora: mix of deciduous trees and drought tolerant evergreen trees. Tropical scrub forest can be found during the dry season and contain mostly small deciduous trees

41 Temperate Deciduous Forest Location: areas w/ moderate average temperatures that change significantly w/ the season (Europe, North & Eastern America, parts or Asia) Climate: long warm summers, cold but not too severe winters, abundant precipitation, often spread fairly evenly yearly Flora; Few species of broadleaf deciduous trees such as oak, hickory, maple, poplar, sycamore. Rich ground level diversity. Drop leaves in fall & become dormant for winter; spring they grow their leaves again Soil: thick layer of surface litter because low decomposition rate. Surface litter is nigh in nutrients Fauna: Home to many species. Predators: bears, wolves, foxes, wildcats, mountain lions. Others: white tailed deer, squirrels, rabbits, opossums, raccoons, mice. Birds: Warblers, Robins

42 Evergreen Coniferous (Boreal) Forests Location: Just south of the arctic tundra in northern regions across North America, Asia, & Europe Climate: Winters are long, dry, & extremely cold ( Northern taigas only receive 6-8 hours of sun a day). Summers are short, w/ mild to warm temperature (19 hours of sun a day) Flora: Few species of evergreen conifer trees (spruce, fir, cedar, hemlock, pine). The small needle-shaped, waxy coated leaves can withstand intense cold & drought of winter. Low plant diversity few species can survive. Soil: Deep layer of surface liter, low decomposition, waxy needles leave soil nutrient poor, acidic, prevents other plants from growing, waterlogged during the summer à muskegs

43 Temperate Rainforests Location: coastal temperate areas with ample rainfall or moisture from dense ocean fog Climate: Winters are mild, summers are cool Fauna: dominated by dense stands of large conifers: Sitka spruces, douglas fir, and redwoods. Trees depend on frequent rains and moisture from summer fog that rolls in off the Pacific

44 Impact of human activities on forest ecosystems Clearing large areas of evergreen forests by loggers in North America, Finland, Sweden, & Canada Mining and flooding for hydroelectric projects destroy forests. Clearing and degradation of tropical rainforests for timber, grazing land, and agriculture: severe erosion of their already nutrient-poor soil Clearing of temperate deciduous forests in Europe, Asia, & North America for timber, cropland, and ubran development. 99.9% of North American temperate deciduous forests have been cleared for such purposes

45 6-6 Mountain Biomes Make up 20% of the earth s land surface A 100 meter gain in in elevation = 100 km change in latitude Above a certain altitude, known as the snow line, temperatures are so cold that the mountain is almost permanently covered by snow and ice

46 Ecological importance of mountains Ice and snow of mountains help regulate the earth climate by reflecting solar radiation back into space. Sea levels depend on the melting of glacial ice, most of it locked in Antarctica Contains most of the world s forests, which contain the majority of the world s biodiversity Freestanding mountains are islands of biodiversity surrounded by a sea of lowerelevation; many mountains are home to endemic species, also sanctuaries for animal species driven from lowland areas Play a critical role in the hydrological cycle by gradually releasing melting ice, snow, and water stored in the soils and vegetation of mountainsides to small streams, then into rivers, and finally oceans

47 Impacts of human activities on mountains Rapidly increasingly population (esp. in developing countries): Many poor people are forced to migrate uphill and try to survive on less stable soils. They use soils unsustainably because of lack of knowledge about how to grow food, raise livestock, and harvest wood Environmental degradation from global boom in skiing, trekking, and other forms of recreation and tourism Changes in climate and levels of UV radiation; global warming increase. Also depletion of ozone can have the same effects: many species of mountain plants could be displaced by lowland species that have higher rates of growth and reproduction Increased commercial extraction of timber and mineral resources: excessive soil erosion, flooding in the valleys below, loss of wildlife habitat, air and water pollution from mining activities Increased air pollution from growing urban and industrial centers and increased automobiles: Trees at high elevations are bathed in air pollutants (ozone and acidic compounds) Dams and reservoirs: flood mountain slopes, and the dams alter the types and abundance of species in rivers

48 6-7 Lessons from Geographic Ecology Different climates occur as a result of currents of air and water flowing over an unevenly heated planet spinning on a tilted axis Different Climates result in different Communities of organisms or biomes Everything is connected