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Chapter 7 Physical Environment

Chapter 7 Physical Environment. 鄭先祐 生態主張者 Ayo Japalura@hotmail.com. 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

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Chapter 7 Physical Environment

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  1. Chapter 7 Physical Environment 鄭先祐 生態主張者 Ayo Japalura@hotmail.com

  2. 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 Chap07 Physical environment

  3. 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) Chap07 Physical environment

  4. Lowest limit of tolerance Highest limit of tolerance Physiological optimum Low tolerance Inability to survive Low tolerance Inability to survive Low population Species absent Species absent Low population Population density Physical gradient (e.g., pH) Fig. 7.1 Organismal distribution along a physical gradient, such as pH. Chap07 Physical environment

  5. Wavy hair grass (Deschampsia flexuosa) Sheep’s fescue (Festucaovina) 3 4 5 6 7 8 3 4 5 6 7 8 Relative species performance Small scabious (Scabiousa columbaria) Common sorrel (Rumex acetosa) 3 4 5 6 7 8 3 4 5 6 7 8 pH at 2 cm depth Fig. 7.2 Ecological optimum curve Physiological optimum curve Chap07 Physical environment

  6. 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) Chap07 Physical environment

  7. 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). Chap07 Physical environment

  8. 40 Latitude 35 30 Minimum temperature Less than -16°C Less than -20°C 25 125 120 115 110 105 100 Longitude Chap07 Physical environment

  9. Fig 7.5 the northern distribution of the vampire bat. 30° 20° Recent records Fossil records Mean minimal temperature for January, 10°C 10° 100° 110° 90° 80° Chap07 Physical environment

  10. 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 Chap07 Physical environment

  11. 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 Chap07 Physical environment

  12. 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) Chap07 Physical environment

  13. Fig. 7.6 Thermophilic giant tubeworms growing at 8,000 feet depth around deep sea vents in the Galapagos rift. Chap07 Physical environment

  14. 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 Chap07 Physical environment

  15. 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) Chap07 Physical environment

  16. 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. Chap07 Physical environment

  17. 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. Chap07 Physical environment

  18. 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 Chap07 Physical environment

  19. 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) Chap07 Physical environment

  20. Greenhouse gases Chap07 Physical environment

  21. Fig 7.8 1800 360 Methane Carbon dioxide 340 1400 320 CO concentration (ppmv) CH concentration (ppmv) 300 1000 280 2 4 260 600 1750 1800 1850 1900 1950 2000 1750 1800 1850 1900 1950 2000 Year Year 0.3 310 Chlorofluorocarbon-11 Nitrous oxide 0.2 300 N O concentration (ppbv) CFC concentration (ppbv) 0.1 290 2 280 0.0 1750 1800 1850 1900 1950 2000 1750 1800 1850 1900 1950 2000 Year Year Chap07 Physical environment

  22. 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 Chap07 Physical environment

  23. 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? Chap07 Physical environment

  24. 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”. Chap07 Physical environment

  25. 0.4 Fig. 7.9 global surface temperature 0.2 0.0 Change from 1940 temperature (°C) -0.2 -0.4 -0.6 1870 1890 1910 1930 1950 1970 1990 Year Chap07 Physical environment

  26. 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 Chap07 Physical environment

  27. 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 Chap07 Physical environment

  28. 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 Chap07 Physical environment

  29. 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

  30. 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 Chap07 Physical environment

  31. Fig. 7.11 predicted changes in precipitation patterns caused by global warming. Chap07 Physical environment

  32. 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 Chap07 Physical environment

  33. Fig. 7.12 This huge live oak tree was felled by strong winds in North Florida. Chap07 Physical environment

  34. 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) Chap07 Physical environment

  35. Fig. 7.13 special salt glands in Spartina leaves exude salt, enabling this grass to exist in saline inter-tidal conditions. Chap07 Physical environment

  36. 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 Chap07 Physical environment

  37. Water • Protoplasm is 85-90% water • Distribution of many plants limited by water availability • Animal distribution affected by desiccation • Tolerance and avoidance Chap07 Physical environment

  38. 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 Chap07 Physical environment

  39. Observed Predicted 600 400 Number of thrips per flower 200 0 1932 1934 1936 1938 1940 1946 1942 Fig. 7.15 Comparison of means of observed annual population densities of thrips with densities predicted by a model. Chap07 Physical environment

  40. 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 Chap07 Physical environment

  41. 25 Lake Manyara gives permanent fresh water 20 2 15 Number of buffalo per km 10 5 500 1500 1000 2000 Fig. 7.16 Rainfall (mm) Chap07 Physical environment

  42. 12 (30.5) 10 (25.4) 8 (20.3) Rainfall ( in (cm) ) 6 (15.2) 4 (10.2) 2 (5.1) 2 1 3 4 5 Fig. 7.17 2 2 Density/ 1000 ft (93m ) Chap07 Physical environment

  43. 7.3 Physical Factors and Numbers of Species • Importance of evapo-transpiration • Figure 7.18 Chap07 Physical environment

  44. 10 20 0 0 30 10 40 40 40 30 60 30 80 100 30 140 120 20 160 180 Fig. 7.18 tree species richness in Canada and US. Contours connect points with the same approximate number of species per quadrant. Chap07 Physical environment

  45. 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. Chap07 Physical environment

  46. (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) Species abundance (3) (4) Fig. 7.19 Environmental gradient Chap07 Physical environment

  47. 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 Chap07 Physical environment

  48. Diseases likely to spread Chap07 Physical environment

  49. Computer model prediction • Average global temperature increase of 3° C • 50-80 million new cases of malaria per year Chap07 Physical environment

  50. 問題與討論！ Japalura@hotmail.com Ayo 台南站： http://mail.nutn.edu.tw/~hycheng/ Chap07 Physical environment

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