Download Chapter 7 Physical Environment

Chapter 7
Physical Environment
鄭先祐
生態主張者 Ayo
[email protected]
Road Map
Physical environment
• Physical variables commonly limit the abundance of
plants and animals
– Resources
– Variables critical to survival
• Physical factors commonly limiting species
–
–
–
–
Extreme temperatures
Wind
Salt
Global climate change
• Physical environment limits abundance and distribution
• Physical environment can alter species composition
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Physical Variables and
Species Abundance
• Liebig’s Law of the Minimum (1840)
– The distribution of a species will be controlled
by that environmental factor for which the
organism has the narrowest range of
tolerance
– Optimum range (Figure 7.1)
– Effects of competition (Figure 7.2)
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Population density
Lowest limit of tolerance
Highest limit of tolerance
Physiological optimum
Inability
to survive
Low
tolerance
Low
tolerance
Inability
to survive
Species
absent
Low
population
Low
population
Species
absent
Physical gradient
(e.g., pH)
Fig. 7.1 Organismal distribution along a physical gradient,
such as pH.
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Wavy hair grass
Sheep’s fescue
Relative species performance
(Deschampsia flexuosa)
3
4
5
6
7
(Festuca ovina)
8
Small scabious
4
5
4
5
6
7
8
Common sorrel
(Scabiousa
columbaria)
3
3
(Rumex acetosa)
6
7
8
3
4
5
6
7
8
pH at 2 cm depth
Ecological optimum curve
Chap07
Physical
environment
Physiological
optimum
curve
Fig. 7.2
5
Physical Variables
• Temperature
– Affects biological processes
– Organism’s inability to regulate body
temperature
• Distribution of Coral Reefs (Figure 7.3)
• Distribution of Larrea tridentata (Figure 7.4)
• Distribution of vampire bats (Figure 7.5)
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30°N
20°C
20°C
30°S
Fig. 7.3 the world distribution of coral reefs
closely matches the 20oC isotherm for the
coldest month of the year(dashed
line).
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Latitude
40
35
30
Minimum temperature
Less than -16°C
Less than -20°C
25
125
120
115
110
Longitude
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environment
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100
8
Fig 7.5 the northern
distribution of the vampire bat.
30°
20°
Recent records
Fossil records
10°
Mean minimal temperature for January, 10°C
110°
100°
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90°
80°
9
Mean temperature vs.
Extreme temperatures
• Frequency of extremes limits species
– Ex. Agriculture and occurrence of freezing
temperatures
• Distribution of oranges in Florida
• Distribution of coffee in Brazil
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Correlations between temperature
and species distribution
– Temperature maps may not coincide with what
organisms experience
– Movement from sun to shade environments
– Temperature at the local scale, is much more
variable
• Ex. Microclimates of a tree
– South-facing vs. north-facing canopy
– Soil surface to top of canopy
• Ex., Rufous grasshopper
– Restricted to steep sunny slopes
– Combination of time and temperature is important
– Degree-days determine development
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High temperature
• High temperatures denature proteins
(temperatures above 45°)
• Organisms effectively cool themselves through
water loss
• Life-history stages resistant to high temperatures
– Resting spores of fungi
– Cysts of nematodes
– Seeds of plants
• Ex. Dry wheat grains (90°)
• Thermus aquaticus (67°)
• Thermophilic bacteria (100°; Figure 7.6)
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Fig. 7.6 Thermophilic giant tubeworms growing
at 8,000 feet depth around deep sea vents in the
Galapagos rift.
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Fire
• North America before the arrival of Europeans
– Fires started by lightening
– Frequent and regular
– Consumed leaf litter, branches and undergrowth before
great quantities accumulated
– Large trees usually not damaged
– Some species evolved to require fire
• Pinus banksiana
• Pinus palustris
• Serotinous cones
•Cones sealed with resin
• Require heat from fire to open
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• North America after the arrival of Europeans
– Management practices
• Maintain “natural” environment
• Preventing forest fires
• Produced the opposite
– Change in species composition
• Catastrophic fires (Figure 7.7)
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Fig. 7.7 (a) when fires burn in a natural cycle, the leaf
litter does not have much time to accumulate and the
fire burns with a moderate heat.
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Fig. 7.7 (b) when fires are suppressed, much litter
accumulates, and any fires that do ignite, quickly get
out of control and burn high in the forest canopy,
killing mature trees.
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Global warming
• Two issues
– Rate of global warming
– Contribution by humans
• Increased global warming = greenhouse effect
– Atmosphere transmits short-wave solar radiation
• 50% passes through the atmosphere unaltered to heat the
earth.
• Energy absorbed by the earth is radiated back to the
atmosphere as long-wave radiation
• Long-wave radiation, much is absorbed by clouds
• A large amount of energy absorbed in the atmosphere is
returned to the earth, causing the temperature to rise
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Earth requires some
"greenhouse effect"
• Without any greenhouse effect
– Global average temperature: -17°
• With greenhouse effect
– Global average temperature: +15°
• Explains hot Venus (blanketed in CO2)
and cold Mars (which has little
atmosphere)
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Greenhouse gases
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340
Carbon dioxide
320
300
280
260
1750 1800 1850 1900
1950 2000
CH concentration (ppmv)
CO concentration (ppmv)
360
1800
1000
600
1750 1800 1850 1900 1950 2000
300
290
280
1750 1800 1850 1900
1950 2000
CFC concentration (ppbv)
N O concentration (ppbv)
Year
Nitrous oxide
Year
Methane
1400
Year
310
Fig 7.8
0.3
Chlorofluorocarbon-11
0.2
0.1
0.0
1750 1800 1850 1900
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Year
1950 2000
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Influence of natural sources
• Nitrous oxide
– 2/3 comes from natural soils and oceans
• Methane
– 1/3 comes from bogs, swamps, and termites
• Dust and carbon
– Volcanoes
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Human influences
• 75% of increases in CO2 emisssions
• 39% of methane output
• 36% of nitrous oxide emissions
• ~50% of all greenhouse emissions
• Alterations in land use (~25%)
– Deforestation
– Conversion to rice paddies
• Increase in domestic animals
• Agricultural soils
– Overall, humans account for 75% of the increase in
greenhouse gases
– Is it possible to replace fossil fuels?
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Evidence of temperature increases
• Temperature record (Figure 7.9)
– Problems with record
• Although the number of recording station may be
large, their geographic distribution is not truly
global.
• Some stations may have experienced
substantial warming due to changes in land use
and population density– the “urban-heat-island
effect”.
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0.4
Change from 1940 temperature (°C)
Fig. 7.9 global surface temperature
0.2
0.0
-0.2
-0.4
-0.6
1870
1890
1910
1930
Year
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1950
1970
1990
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Computer models and predictions
• Too many variables to include in a single computer
model.
• Negative feedback mechanisms
• Positive feedback mechanisms
• UN Intergovernmental Panel on Climate Change
(IPCC)
– 1996 report
– Lack of fit of models
• Emphasizes the complexity of interactions
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Environmental impact
• Speed and extent of global warming
• Focus on 2100
– Atmospheric CO2 will have doubled
– Temperature will have risen 1 to 3.5° C
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Natural ecosystems
• Profound changes in natural ecosystems
• Most species cannot evolve significantly or
rapidly enough to counter climate changes
• Most species will not be able to disperse or
migrate fast enough to keep up with
climate change
– Figure 7.10
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400 km
Fig. 7.10 The geographic range of sugar
maple(blue shading)and its potentially suitable
range under doubled CO2 levels (yellow shading)
in North America.Chap07 Physical environment
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Rainfall patterns
• Increase in rainfall (Figure 7.11) in most
areas
– Increase crop production
– Ex. Tropical countries and rice production
• Decrease in some areas already dry
– Midcontinental America and Asia
• More droughts
• More extinctions
• Current grain producing areas would become
drier
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Fig. 7.11 predicted changes in precipitation patterns caused by
global warming.
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Wind
• Can be caused by temperature gradients
• Amplifies temperature effects on organisms
– Increase heat loss through evaporation and convection
– Increases animal evaporation and plant transpiration
• Wind aids pollination
• Wind disperses plant seeds
• Affects mortality (Figure 7.12)
– High winds
– Severe storms
• Modify wave action
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Fig. 7.12 This huge live oak tree was felled by strong
winds in North Florida.
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Salt
• Increases osmotic resistance to water
uptake
– Occurs in arid regions
– Important to agriculture in arid regions
• Increases salt concentration
• Decreases crop yield
– Salt marshes
• Halophytes
• Adapted to high salt concentrations
• Ex. Spartina grasses (Figure 7.13)
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Fig. 7.13 special salt glands in Spartina leaves exude
salt, enabling this grass to exist in saline inter-tidal
conditions.
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pH
• Few organisms can exist below pH 4.5
– Ex. Lake trout in Eastern US disappear when pH
drops below 5.2
• Roots are damaged below pH 3 and above 9
– Calciphobe: only grow on acidic soils
– Calciphiles: only grow in basic soils
– Neutrophiles: tolerant of either condition
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Water
• Protoplasm is 85-90% water
• Distribution of many plants limited by
water availability
• Animal distribution affected by desiccation
• Tolerance and avoidance
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7.2 Physical Factors and
Species Abundance
• Davidson, Andrewartha, and Birch
– Thrips (Figure 7.14 + Figure 7.15)
– Fed on rosebushes
– Counted every 81 consecutive days
– 78% of variation in population maxima was accounted for
by weather
– Predict the number of thrips using multiple regressions
• Log y = -2.39 + 0.125a + 0.201b + 0.186c +0.085d
–
–
–
–
–
Log y = log of thrip density
a = winter temperature
b = spring rainfall
c = spring temperature
d = size of overwinter population
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Observed
Predicted
600
400
200
0
1932
1934
1936
1938
1940
1942
1946
Fig. 7.15 Comparison of means of observed annual population
densities of thrips with densities predicted by a model.
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Rainfall
• Africa Buffalo and environmental regulation
– Rainfall and grass productivity in the Serengeti
– Buffalo density regulated by food availability
– Figure 7.16
• Woddell, Mooney, and Hill (1969)
– Correlation between rainfall and creosote bush
density
– Figure 7.17
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25
Lake Manyara gives
permanent fresh water
Number of buffalo per km 2
20
15
10
5
500
1000
Rainfall (mm)
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1500
Fig. 7.16
2000
41
12
(30.5)
Rainfall ( in (cm) )
10
(25.4)
8
(20.3)
6
(15.2)
4
(10.2)
2
(5.1)
•Fig. 7.17
1
2
3
4
1000 2 ft (93m 2)
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7.3 Physical Factors and
Numbers of Species
• Importance of evapo-transpiration
– Figure 7.18
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10
20
0
0
30
40
40
10
40
30 60
30
80
100
30
20
120
140
160
180
Fig. 7.18 tree species richness in Canada and US.
Contours connect points with the same approximate
number of species per
quadrant.
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Physical Factors and Numbers
of Species
• Robert Whittaker (1969)
– Four hypotheses explaining distribution patterns
– Figure 7.19
• (1) competition caused sharp boundaries among distinct groups
• (2) competition caused sharp boundaries between species
• (3) physical variables cause distinct boundaries between groups.
• (4) physical variable cause distinct boundaries between species.
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(1) competition caused sharp boundaries among distinct groups
(2) competition caused sharp boundaries between species
(3) physical variables cause distinct boundaries between groups.
(4) physical variable cause distinct boundaries between species.
Species abundance
(1)
(2)
(3)
(4)
Fig. 7.19
Environmental gradient
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Diseases and Global climate
change
• Spread of tropical diseases poleward
– Controlled by the range of their vectors
• Ex. Mosquitoes and other insects
• Insects are ectotherms
– Increase in temperature = increase in range and
activity of vectors
• Ex. Rwanda 1987
– 1° C increase in temperature resulted in a 337%
increase in malaria
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Diseases likely to spread
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Computer model prediction
• Average global temperature increase of 3° C
– 50-80 million new cases of malaria per year
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 問題與討論！
[email protected]
Ayo 台南站： http://mail.nutn.edu.tw/~hycheng/
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