GEOG5839.06, The principle of cross dating

1,162 views
979 views

Published on

Published in: Education, Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,162
On SlideShare
0
From Embeds
0
Number of Embeds
289
Actions
Shares
0
Downloads
36
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

GEOG5839.06, The principle of cross dating

  1. 1. September 20 The principle of cross-datingSource: Baillie (1982)
  2. 2. GEOG5839FROM LIMITS TO PATTERNS
  3. 3. h p://esp.cr.usgs.gov/data/atlas/li le/
  4. 4. Isolated populations ** x *MAIN RANGE DISCONTINUOUS TEMPORARY RANGE POPULATIONS * * x ** Individual adults x populations Extinct (not reproducing)
  5. 5. h p://esp.cr.usgs.gov/data/atlas/li le/
  6. 6. Source: Elroy
  7. 7. Source: Bryant Olsen
  8. 8. Source: Phil Camill
  9. 9. THE LAW OF THE MINIMUM Growth is controlled by the scarcest resource (limiting factor), not the total amount of resources available
  10. 10. Average temperatures are remarkably consistent at treeline locations around the world.Source: Körner and Paulsen, Journal of Biogeography, 2004
  11. 11. temperature water day length
  12. 12. h p://esp.cr.usgs.gov/data/atlas/li le/
  13. 13. “COMPLACENT”
  14. 14. “SENSITIVE”
  15. 15. Weather and climate act to synchronize growth ratesat the level of the cell, the tree, the forest and beyond.
  16. 16. “ RINGS ” IN THE BRANCHES OF SAWED TREES SHOWTHE NUMBER OF YEARS AND, ACCORDING TO THEIR THICKNESS, THE YEARS WHICH WERE MORE OR LESS DRY. Leonardo da Vinci
  17. 17. Tree-ring width is not just a function of wet and dry
  18. 18. Same environmental forcings Similar growth pa erns
  19. 19. GEOG5839 CHRONOLOGY
  20. 20. THE PRINCIPLE OF CROSS-DATINGMatching pa erns in tree-ring widths or other ring characteristics(such as ring density) among several trees allow the identificationof the exact year in which each ring was formed.
  21. 21. Photograph: Dan Griffin
  22. 22. 3Different approaches
  23. 23. THE ‘LIST’ METHOD
  24. 24. THE PRINCIPLE OF CROSS-DATING 1900 1910 1920 1930 Two Douglas-fir cores from Eldorado Canyon, COSource: Jeff Lukas, INSTAAR
  25. 25. SKELETON PLOTTING
  26. 26. Compare rings to their neighbors.
  27. 27. RING MEASUREMENT
  28. 28. Source: Hughes and Brown, 1992
  29. 29. GEOG5839PROBLEMS WITH DATING
  30. 30. Why can’t you just count the rings back in time?
  31. 31. COMPLICATION #1 “Micro” rings
  32. 32. Ponderosa pine Pinus ponderosaSource: Peter Brown
  33. 33. COMPLICATION #2 Partial rings
  34. 34. Limber pinePinus flexilis
  35. 35. COMPLICATION #3 Missing rings
  36. 36. Picture not available.
  37. 37. PLE -RING SAM EE HE TR N WH ERE T OSITI O LLEC TED!AT THE P WA S CO A “missing ring” is a term used to describe the phenomenon where a tree does not form wood around its trunk during a single growing season.
  38. 38. COMPLICATION #4 False rings
  39. 39. Ponderosa pine Pinus ponderosaSource: Peter Brown
  40. 40. Arizona cypress Cupressus arizonicaSource: Peter Brown
  41. 41. Falsering boundary sharp gradual Annual ring boundary
  42. 42. Why can’t you just count the rings back in time?
  43. 43. GEOG5839 PUZZLES IN TIME
  44. 44. Widespread drought caused narrow rings to form across the southwest USA during 1748 and 1750.Source: Kurt Kipfmueller
  45. 45. COMPLICATION #5 No outer date
  46. 46. Bur oak (Quercus macrocarpa) is a common tree along rivers in Minnesota and the upper Midwest.Select trees of this species can live for up to 450 years.
  47. 47. Photo: Erik Nielsen
  48. 48. 68Photo: Erik Nielsen
  49. 49. 69
  50. 50. What kind of trees have rings that can be dated? • They have distinct and detectable rings. • Their rings must be reliably annual. • The formation of their rings must be sensitive to environmental conditions. • That sensitivity must cause the rings to vary from year to year. • Several trees must share common pa erns in tree-ring width, wood density or some other wood variable.
  51. 51. ‘Complacent’
  52. 52. ‘Complacent’ tree-ring series: • exhibit very li le year-to-year variation. • grow in se ings where the limiting growth factor doesn’t change much. • are tough to cross-date.
  53. 53. Tucson AZ
  54. 54. ‘Sensitive’
  55. 55. ‘Complacent’ tree-ring series: • exhibit very li le year-to-year variation. • grow in se ings where the limiting growth factor doesn’t change much. • are tough to cross-date.‘Sensitive’ tree-ring series: • have wide and narrow rings that are intermixed through time. • Found in environments where the limiting factor is highly variable year to year • Matching ring pa erns across trees is easier.
  56. 56. September 20 The principle of cross-datingSource: Baillie (1982)
  57. 57. GEOG8280 XT C L AS SNE

×