Chapter 7 Physical Environment 鄭先祐生態主張者 Ayo [email protected].

Chapter 7 Physical Environment

鄭先祐生態主張者 Ayo

[email protected]

Chap07 Physical environment 2

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

Road Map


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)


Lowest limit of tolerance

Physiological optimum

Highest limit of tolerance

Low tolerance

Low population

Inabilityto survive

Speciesabsent

Low tolerance

Low population

Inabilityto survive

Speciesabsent

Physical gradient (e.g., pH)

Pop

ula

tion d

ensi

ty

Fig. 7.1 Organismal distribution along a physical gradient, such as pH.


3 4 5 6 7 8 3 4 5 6 7 8

3 4 5 6 7 8 3 4 5 6 7 8

Ecological optimum curvePhysiological optimum curve

Rela

tive s

peci

es

perf

orm

ance

pH at 2 cm depth

Wavy hair grass(Deschampsia flexuosa)

Sheep’s fescue(Festuca ovina)

Small scabious(Scabiousa columbaria)

Common sorrel(Rumex acetosa)

Fig. 7.2


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)


20°C

20°C

30°N

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).


Minimum temperature

Less than -16°C

Less than -20°C

Longitude

Lati

tude

25

30

35

40

125 120 115 110 105 100


30°

20°

10°

110° 100° 90° 80°

Recent records

Fossil records

Mean minimal temperature for January, 10°C

Fig 7.5 the northern distribution of the vampire bat.


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


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


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)


Fig. 7.6 Thermophilic giant tubeworms growing at 8,000 feet depth around deep sea vents in the Galapagos rift.


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


• 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)


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.


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.


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


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)


Greenhouse gases


Carbon dioxide Methane

Nitrous oxideChlorofluorocarbon-11

260

280

300

320

340

360

280

290

300

310

600

1000

1400

1800

1750 1800 1850 1900 1950 2000

Year

0.0

0.1

0.2

0.3

CO

c

on

cen

trati

on

(pp

mv)

CH

c

on

cen

trati

on (

pp

mv)

CFC

con

cen

trati

on (

pp

bv)

N O

conce

ntr

ati

on (

ppbv)

22 4

1750 1800 1850 1900 1950 2000

Year

1750 1800 1850 1900 1950 2000

Year

1750 1800 1850 1900 1950 2000

Year

Fig 7.8


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


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?


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”.


1870 1890 1910 1930 1950 1970 1990

Year

Chang

e f

rom

19

40 t

em

pera

ture

(°C

)

-0.6

-0.4

-0.2

0.0

0.2

0.4

Fig. 7.9 global surface temperature


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


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


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


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.


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


Fig. 7.11 predicted changes in precipitation patterns caused by global warming.


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


Fig. 7.12 This huge live oak tree was felled by strong winds in North Florida.


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)


Fig. 7.13 special salt glands in Spartina leaves exude salt, enabling this grass to exist in saline inter-tidal conditions.


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


Water

• Protoplasm is 85-90% water

• Distribution of many plants limited by water availability

• Animal distribution affected by desiccation

• Tolerance and avoidance


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


Observed

Predicted600

400

200

0

Num

ber

of

thri

ps

per

flow

er

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.


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


500 1000 1500 2000

5

10

15

20

25

Rainfall (mm)

Num

ber

of

buff

alo

per

km2

Fig. 7.16

Lake Manyara gives permanent fresh water


Rain

fall

( in

(cm

) )

1 2 3 4 5

12(30.5)

10(25.4)

8(20.3)

6(15.2)

4(10.2)

2(5.1)

Density/ 1000 ft (93m )2 2•Fig. 7.17


7.3 Physical Factors and Numbers of Species

• Importance of evapo-transpiration

– Figure 7.18


10

00

10

20

30

40

30

30

30

20 120

100140

160

180

80

60

4040

Fig. 7.18 tree species richness in Canada and US. Contours connect points with the same approximate number of species per quadrant.


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.


(1)

(2)

(3)

(4)

Sp

eci

es

ab

und

an

ce

Environmental gradient

(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.

Fig. 7.19


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


Diseases likely to spread


Computer model prediction

• Average global temperature increase of 3° C

– 50-80 million new cases of malaria per year


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Ayo 台南站： http://mail.nutn.edu.tw/~hycheng/

Chapter 7 Physical Environment 鄭先祐生態主張者 Ayo [email protected].

Documents

Transcript of Chapter 7 Physical Environment 鄭先祐生態主張者 Ayo [email protected].

Chapter 7 Physical Environment 鄭先祐 生態主張者 Ayo [email protected].

Documents

Transcript of Chapter 7 Physical Environment 鄭先祐 生態主張者 Ayo [email protected].

Chapter 7 Physical Environment 鄭先祐生態主張者 Ayo [email protected].

Transcript of Chapter 7 Physical Environment 鄭先祐生態主張者 Ayo [email protected].