Plant Ecology - Chapter 21

1. Plant Ecology - Chapter 21 Global Change: Humans & Plants

2. Acid Deposition

3. NO from cars Automobiles as a Source

4. Widespread Secondary Air Pollution: Acid Deposition • Wet deposition • Dry deposition

5. Acid Deposition in the U.S.

6. Acid Deposition, Plants, and Soil

7. Acid Deposition, Plants, and Soil • Lowers soil pH • Affects mineral solubility • Leach out positively charged ions (K, Mg, Ca) from clay particles • Easily flushed away

8. Acid Deposition, Plants, and Soil • Increases concentration of potentially toxic minerals • E.g., aluminum • Damages xylem - reduces ability to take in water, nutrients - die from lack of moisture, nutrients

9. Acid Deposition, Plants, and Soil • Direct damage to forest tree foliage • Erodes protective waxes from leaves, needles • Leaches nutrients from leaves

10. Acid Deposition, Plants, and Soil • Has resulted in loss of large stands of trees in many different regions around world • Canada, New England, Smoky Mountains

11. Acid Deposition, Plants, and Soil

12. Acid Deposition, Plants, and Soil • Nearly 70% of forests in Czech Republic have been destroyed • Trees in nearly half of Germany’s Black Forest have been impacted

13. Acid Deposition, Plants, and Soil • Switzerland has lost 10% of its forests • Increased chance of avalanches

14. Acid Deposition, Plants, and Soil • Large portions of forests in Norway have been lost, especially in southern regions

15. Acid Deposition, Plants, and Soil • Correlation between dying forests and thriving ground layer of mosses

16. Acid Deposition, Plants, and Soil • Mosses are acid-loving • Thick layer holds do much moisture that surface soils become saturated • Feeder roots, tree die from lack of oxygen (drown)

17. Acid Deposition, Plants, and Soil • Mosses also may kill mycorrhizal fungi • Reduce uptake of nutrients

18. Acid Deposition, Plants, and Soil • Dense layer of mosses may further acidify water passing through them into soil • Dissolve more toxic trace metals, leach more soil nutrients

19. Acid Deposition, Plants, and Soil • Even if trees somehow manage to survive all these problems, their growth is reduced substantially

20. Acid Deposition, Plants, and Soil

21. Acid Deposition, Plants, and Soil • Varying effects on crop productivity, but wide distribution

22. Acid Deposition, Plants, and Soil • Some evidence for direct damage • Potatoes in Canada - damage to foliage, potential uptake of toxins

23. Acid Deposition, Plants, and Soil • Coffee plants have shown damage to foliage in some areas

24. Acid Deposition, Plants, and Soil • Although much evidence points toward harmful effects from acid rain, some studies show the opposite

25. Acid Deposition, Plants, and Soil • Helpful to crops where soil nutrients may be very low - nitrogen-limited • Acidification may release nutrients, allow for greater uptake

26. Acid Deposition, Plants, and Soil • Some evidence where crops show now effect of acid deposition, either negative or positive • Balance each other out

27. Acid Deposition and Aquatic Systems • Fish declines • Undesirable species • Aluminum toxicity • Acid shock

28. Global Carbon Cycle Human effects: fossil fuel combustion, cutting and burning of trees

29. Global Carbon Cycle

30. Global Carbon Cycle • Increasing atmospheric CO2 has brought about a rise in global temperature

31. Greenhouse Effect • CO2 acts like glass in a global greenhouse • Slows escape of infrared radiation from earth’s surface

32. Greenhouse Effect • Many other gases are far more effective at trapping heat • Methane, CFCs, nitrous oxide (N2O) • 20-270 X as effective • CO2 responsible for 2/3 of increase in greenhouse effect

33. Greenhouse Effect • CO2 concentrations increased 21.5% from 1870-1990 • Increasing consumption of fossil fuels, deforestation • Doubling of CO2 concentrations may occur with continued fossil fuel use over 50-100 years

34. Greenhouse Effect • CO2 doubling may increase average global temperature by 2-5°C • Global temps have increased 0.8°C over last century, 0.6° of that in last 30 years

35. Major Climate Changes • Worldwide change in patterns of precipitation, storms, winds, ocean currents • Each 1°C increase pushes climatic zones 90 mi N in N. hemisphere

36. Major Climate Changes • Variable effects worldwide, but greatest changes between 40 and 70°N, in N. Amer. and Eurasia • Caused by both warmer temps and increased CO2 (greater forest productivity)

37. Major Climate Changes • Polar ice sheets and glaciers have been melting, and changes would escalate

38. Major Climate Changes • Sea levels would rise due to melting ice, expansion of warming water • 4°C increase would cause 0.5-1.5 m rise worldwide • Flood coastal wetlands, low-lying cities, agricultural lands

39. Major Climate Changes • Frequency, intensity of weather extremes would increase • Heat waves, drought, hurricanes

40. Major Climate Changes • Speed up decay of organic matter • Further increase CO2 concentrations in atmosphere

41. Major Climate Changes • Warmer climates spreading northward would bring insect-borne diseases, more pests into areas currently protected by cold temperatures

42. Major Climate Changes • Growth rates of many tree species would be lowered • Ranges would have to shift northward • At rate up to 10 X greater than they’ve ever done in the past • Birch, sugar maple

43. Major Climate Changes • Stress from pests, disease microorganisms would increase • Adapt faster than tress to changing environments

44. Major Climate Changes • More frequent fires • Forest and grassland • Increased disturbance: decreased diversity?

45. Declining Global Biodiversity • 300,000 plant species have been described and named • 1.5 million species of all kinds • At least 5-10 million living species not described • What’s out there?

46. Declining Global Biodiversity • Many large species may be at risk of extinction • But so may many unknown or little known forms (like mycorrhizae) • Also may lose genetic diversity as some populations disappear, losing unique genes

47. Declining Global Biodiversity • Many current threats to global diversity • Changes in land use is greatest • Destruction, degradation, fragmentation

48. Habitat Loss • Outright loss of habitat • Varying degree of disturbance - elimination of important species, soil damage, overgrazing, altered disturbance regime

49. Biodiversity Hotspots

50. Biodiversity Hotspots • 25 areas - 1.4% of earth’s land surface • Contain half of world’s known plant species • Regions have lost 88% of original vegetation cover