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BIOL 4120: Principles of EcologyBIOL 4120: Principles of Ecology
Lecture 22: Biogeographical Lecture 22: Biogeographical EcologyEcology
Dafeng HuiDafeng Hui
Room: Harned Hall 320Room: Harned Hall 320
Phone: 963-5777Phone: 963-5777
Email: [email protected]: [email protected]
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23 Terrestrial Ecosystems23 Terrestrial Ecosystems
23.1 Biomes and climate 23.2 Tropical forests (Equatorial zone)23.3 Tropical savannas (semiarid regions with
seasonal rainfall)23.4 Desert23.5 Temperate zone (Mediterranean climate)23.6 Forest ecosystems (Temperate wetter
regions)23.7 Grassland ecosystems (Temperate zone
vary with climate and geography23.8 Conifer forests (cool temperature and boreal
zones)23.9 Arctic tundra (cold temperatures and low
precipitation)
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Biomes are classified according to the
predominat plant types
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Concept of Biomes:
F.E. Clements and V.E. Shelford, 1939
Combining broad-scale distribution of both plants and associated animals into a single classification
Biomes: classified according to the predominant plant types
Campbell 1996: the world's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment.
Major terrestrial biome types:
Tropic forest, temperate forest, conifer forest (taiga and boreal forest), tropical savanna, temperate grasslands, chaparral (shrublands), tundra, and desert.
three general plant forms: trees, shrubs, and grasses.
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Robert Whittaker, Cornell Uni.
Biomes and climate
Boundaries between biomes are broad and often indistinct
Other factors: topography, soils, and exposure to disturbances such as fire
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23.1 Terrestrial ecosystems reflect adaptations of dominant plant life forms
Why are there consistent patterns in the distribution and abundance of three dominant plant life forms that relate to climate and physical environment?
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Terrestrial ecosystems reflect adaptations of dominant plant life forms
These three forms represent different patterns of carbon allocation and morphology
Grass: less C to production of supporting tissue (stem) than do wood plants (shrubs and trees), more to photosynthetic tissues (leaves)
Woody plants: shrubs allocate lower percentage to stem than trees.
Trees: more to stem, advantage of height and access to light, cost more for maintenance and respiration.
As environmental conditions become adverse for photosynthesis (dry, low nutrient, cold T), trees will decline in both stature and density until they are no longer able to persist as a component of the plant community.
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Forests
Within broad classes of forest and woodland ecosystem (trees are dominant or co-dominant), leaf form is another plant characteristic.
Based on longevityDeciduous (live for only one year or growing season)• Winter-deciduous (temperate regions, low winter T)• Drought-deciduous (subtropical and tropical, leaf shed on
dry periods)Evergreen (live beyond a year)• Broadleaf-evergreen (tropic rainforest, no distinct growing
season, year-round photosynthesis)• Needle-leaf evergreen (growing season is short or nutrient
availability constrains photosynthesis and plant growth)
Economic model to explain adaptation of leaf form: cost to produce leaf and gain from photosynthesis.
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Ecosystems characteristic of warm, wet climates with no distinct seasonality are dominated by broadleaf evergreen trees (tropic or subtropical rain forest).
As conditions become drier, with a distinct dry season, broadleaf evergreen habit gives way to drought-deciduous trees (seasonal tropical forest)
As PPT declines further, trees decline and giving rise to woodland and savannas (shrub and grasses).
PPT further declines, no trees can be supported, giving rise to arid shrubland and desert.
Similar for T control.
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Winter-deciduous
Drought-deciduous
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Broadleaf evergreen in tropic rain forest in Australia
Needle-leaf evergreen in Sierra Nevada, US
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23.2 Tropic rain forest
Location: Equatorial zone between latitudes 10oN and 10oS
T: warm all year, annual mean T>18oCPPT: rainfall occurs daily, min.
monthly>60mmTypical example: Amazon basin of
South America
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Tropic rain forests in Amazon (a), Malaysia (b), and Northeast Australia (c)
High net primary productivity (NPP)
High diversity of plant and animal life
7% land surface, >50% plant and animal species
10-km2 contain 1500 species of flowing plants and 750 tree species.
Richest area in Malaysia, 7900 species
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90% of all primate species live in the tropical rain forest
orangutan (an arboreal ape)
Gibbons, langurs, macaques
(Malaysian)
Gorillas, and chimpanzees
(Africa)
Lemurs
Beetles, butterflies
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Vertical stratification of a tropic rain forest
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Plank-like buttresses
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Tropical dry forest
drought-deciduous trees
Africa, South America, Central America, Australia, India, Southeast Asia
Undergo a dry season, influenced by the seasonal migration of Intertropical Convergence Zone (ITCZ)
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23.3 Tropic Savannas
Location: Equatorial zone between latitudes 30oN and 30oS, Dry tropic and subtropical.
T: warm all year, annual mean T>18oCPPT: distinct seasonality in rainfall,
large interannual variationTypical example: South America
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Tropic SavannasSavanna: means the treeless areas of South America
An array of vegetation types representing a continuum of increasing cover of woody vegetation, from open grassland to widely spaced shrubs or trees to woodland
CharacteristicsOccur on land surfaces of little relief, often on old plateaus,
interrupted by escarpments and dissected by riversPoor in nutrients, especially PDominant species are fire-adapted, subjected to recurrent
fires.Grass cover with or without wood vegetation is always presentWoody component is short-lived (less than a few decades).Two-lay vertical structure (ground level grass + shrubs or
trees)Support a large and varies assemblage of herbvores,
invertebrate and vertebrate, grazing and browsing.
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Interaction between annual PPT and soil texture in defining biomes
Access by plants to soil moisture is more limited on the heavy textured soils (clay) than sandy oil.
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23.4 Desert
Area: 25 to 35%Location: latitudes between 15 and 30oCause: Global air mass circulation T: High in summer, could be cold in winterPPT: low, <150 mmTypical examples: majority in Northern
Hemisphere, Sahara in Africa, Gobi in Asia, western North America
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Deserts are not the same everywhere
Cold desert: Great Basin of North America, the Gobi, Takla Makan, and Turkestan deserts of Asia
Species: sagebrush, shadscale, chenopods, etc
Hot desert: Mojave, the Sonoran, and Chihuahuan
Vegetation: none to some combination of chenopods, dwarf-shrubs, and succulents
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Hot desert: a. Chihuahuan Desert, b. Great Victorian Desert in Australia, c. Dunes in Saudi Arabian desert.
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DesertSurvive of desert plants:
Adapted to scarcity of water, low primary productivityFlowering only when moisture is presentFast grow, flower, produce seeds and dieDeep-rooted (mesquite, taproots reach water table)CAM pathway, species leaf structure
Survive of animalsSupport a diversity of animal life (bettles, ants, locusts, lizards, snakes, birds and mammals)Grazing herbivores: generalists, consume a wide range of species. Desert carnivores,such as fox and coyotes, have mixed diet include leaves and fruits.
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23.5 Temperate shrublands
Shrublands: shrub is dominant or co-dominant, but difficult to categorize
Shrub: no good definition, a plant with multiple woody, persistent stems but no central trunk and a height from 4.5 to 8 m.
(Tree can grow less than 8m under severe environmental conditions)
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Temperate shrublands
Location: between latitudes 30o and 40o, five regions
T: hot dry summers, cool, moist wintersPPT: 65% annual PPT falls during winter
months.Five regions: semiarid region of western
North America, regions bordering Mediterranean Sea, central Chile, cape region of south Africa, south-western and southern Australia
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Chaparral is the dominant mediterranean shrub vegetation of southern California
Mediterranean vegetation (fynbos) of the western cape region of South Africa
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23.6 Forest Ecosystems
Forest ecosystems dominate the wetter regions of the temperate zone
Deciduous forest covered large area of Europe and China, but mostly converted to croplands, only exist in eastern China
Southern Hemisphere, temperate evergreen forest become predominant
North America, deciduous forests consist of a number of associations (show later)
Asiatic broadleaf forest found in eastern China, Japan, Korea is similar to the North American deciduous forest
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Large scale distribution of temperature forest in eastern US (showed before?)
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Temperate forest in fall and spring
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23.7 Grassland ecosystems
Rainfall is very important: 250 to 800 mmOther factors: fire, and human activity
(convert from forest to grassland)Area: dropped from 42% to <12% of original
sizeLocation: mid-latitudes in mid-continental
regionsTypical: prairies of North America, steppes of
central Eurasia
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Grassland in North America
a. Tallgrass prairie in Iowa, b. mixed-grass prairie; c. shortgrass steppe
Tallgrass prairie
Big bluestem, >1m
Mixed-grass prairie
Needlegrass-grama grass
Shortgrass prairie
Blue grama and buffalo grass
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Aboveground primary productivity is related to MAP (52 grassland)
Grasslands are most productive when MAP>800 mm and MAT > 15oC
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23.8 Conifer forests
Conifer forests: needle-leaf evergreenLocation: Northern Hemisphere and mountain
rangesVarious composition: wide range of climate they can
growEurope: Norway spruceNorth America: Rocky: Engelmann spruce, subalpine
fir; Douglas-fir, ponderosa pine, lodgepool pine; giant sequoia (in California Sierra)
Boreal forest (11% of Earth’s land surface) Alaska and Canada in N. America, Euroasia (from
Scotland to northern Japan)
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Black spruce in North America taiga (boreal forest)
Some coniferous forest. A. Norway spruce, b. Rocky Mountaine subalpine forest, c. montane coniferous forest in Rocky Mountains
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23.9 Arctic TundraTundra is treeless plainArctic tundra is a frozen plain, clothed in sedges, heaths, and
willows, dotted with lakes, and crossed by streamsCold Temperature and low precipitation
Two types:tundra: up to 100% plant coverage, wet to moist soilpolar desert: dry soil, less than 5% plant cover
Unique conditions:permafrost: isolate and protect soil OMvegetation: simple form, slow growth, allocate more to rootstransfer of heat
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Principles of EcologyWhat we covered in this course:
Ecology is study of interaction of Organisms and environmental conditions
Organisms: adaptation and evolution, life history
Environmental conditions: Climate, terrestrial and aquatic environments
Subdisplinary of ecology
Population ecology: growth, competition, predation, parasitism
Community ecology: structure and dynamics, influence factors
Ecosystem ecology: Ecosystem energetic, decomposition, biogeochemical cycle
Global change ecology: climate change and ecosystem researches
Others: biogeography, human ecology
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Thank you!
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