How do we know tree rings are annual?
The “pinning” method   Photograph: Keith Weston
Band dendrometer
Photograph: Baillie (1982)
P R I N C I P L E S O F C R O S S - DAT I N G
Scots pine                                  Pinus sylvestrisPhotograph: Fritz Schweingruber
temperature   water   day length
Climate acts to synchronize growth rates at thelevel of the cell, the tree, the forest and beyond.
“ RINGS    IN THE BRANCHES OF    SAWED TREES SHOWTHE NUMBER OF YEARS  AND, ACCORDING TO THEIR     THICKNESS,   THE YEARS W...
Tree-ring width is not just a  function of wet and dry
THE PRINCIPLE OF LIMITING FACTORS The rates of biological processes in trees, including the formation of woody cells, are ...
temperature   water   day length
Same environmental forcings                                      Similar                              growth pa erns
THE PRINCIPLE OF CROSS-DATINGMatching pa erns in tree-ring widths or other ring characteristics(such as ring density) amon...
How cross-dating works.
Photograph: Dan Griffin
When was the outer ring formed?
Why can’t you just count the rings back in time?
COMPLICATION #1  “Micro” rings
Ponderosa pine                          Pinus ponderosaPhotograph: Peter Brown
COMPLICATION #2   Partial rings
Limber pinePinus flexilis
COMPLICATION #3  Missing rings
Picture not available.
A “missing ring” is a term used to describe the phenomenonwhere a tree does not form wood around its trunk during a       ...
A “missing ring” is a term used to describe the phenomenonwhere a tree does not form wood around its trunk during a       ...
COMPLICATION #4   False rings
Ponderosa pine                          Pinus ponderosaPhotograph: Peter Brown
Arizona cypress                          Cupressus arizonicaPhotograph: Peter Brown
Falsering boundary                  sharp gradual                    Annual                ring boundary
COMPLICATION #5  No outer date
Photo: Erik Nielsen
47Photo: Erik Nielsen
48
THE PRINCIPLE OF CROSS-DATING                          1900            1910              1920              1930           ...
THE ‘LIST’ METHOD
S K E L E TO N P LOT T I N G
Photograph: Baillie (1982)
Ring width             Tree age
Compare rings to their neighbors.
Marking tree-ring specimens for dating                 decade                 half-century                 century        ...
RING MEASUREMENT
Source: Hughes and Brown, 1992
Widespread drought caused narrow rings  to form across the southwest USA  during 1748 and 1750.Source: Kurt Kipfmueller
What kind of trees have rings that can bedated?    • They have distinct and detectable rings.    • Their rings must be rel...
‘Complacent’
‘Complacent’ tree-ring series:    • exhibit very li le year-to-year variation.    • grow in se ings where the limiting gro...
‘Sensitive’
‘Complacent’ tree-ring series:    • exhibit very li le year-to-year variation.    • grow in se ings where the limiting gro...
Tucson AZ
PRE-WORK ASSIGNMENTBefore next class, try cross-dating online
h p://www.ltrr.arizona.edu/skeletonplot/introcrossdate.htm              or google ‘LTRR skeleton plot’
P R I N C I P L E S O F C R O S S - DAT I N G
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GEOG3839_6_CrossDating

  1. 1. How do we know tree rings are annual?
  2. 2. The “pinning” method Photograph: Keith Weston
  3. 3. Band dendrometer
  4. 4. Photograph: Baillie (1982)
  5. 5. P R I N C I P L E S O F C R O S S - DAT I N G
  6. 6. Scots pine Pinus sylvestrisPhotograph: Fritz Schweingruber
  7. 7. temperature water day length
  8. 8. Climate acts to synchronize growth rates at thelevel of the cell, the tree, the forest and beyond.
  9. 9. “ 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
  10. 10. Tree-ring width is not just a function of wet and dry
  11. 11. THE PRINCIPLE OF LIMITING FACTORS The rates of biological processes in trees, including the formation of woody cells, are constrained by the primary environmental variable that is most limiting.
  12. 12. temperature water day length
  13. 13. Same environmental forcings Similar growth pa erns
  14. 14. 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.
  15. 15. How cross-dating works.
  16. 16. Photograph: Dan Griffin
  17. 17. When was the outer ring formed?
  18. 18. Why can’t you just count the rings back in time?
  19. 19. COMPLICATION #1 “Micro” rings
  20. 20. Ponderosa pine Pinus ponderosaPhotograph: Peter Brown
  21. 21. COMPLICATION #2 Partial rings
  22. 22. Limber pinePinus flexilis
  23. 23. COMPLICATION #3 Missing rings
  24. 24. Picture not available.
  25. 25. A “missing ring” is a term used to describe the phenomenonwhere a tree does not form wood around its trunk during a single growing season.
  26. 26. A “missing ring” is a term used to describe the phenomenonwhere a tree does not form wood around its trunk during a single growing season. At the position where the tree-ring sample was collected!
  27. 27. COMPLICATION #4 False rings
  28. 28. Ponderosa pine Pinus ponderosaPhotograph: Peter Brown
  29. 29. Arizona cypress Cupressus arizonicaPhotograph: Peter Brown
  30. 30. Falsering boundary sharp gradual Annual ring boundary
  31. 31. COMPLICATION #5 No outer date
  32. 32. Photo: Erik Nielsen
  33. 33. 47Photo: Erik Nielsen
  34. 34. 48
  35. 35. THE PRINCIPLE OF CROSS-DATING 1900 1910 1920 1930 Two Douglas-fir cores from Eldorado Canyon, COGraphic: Jeff Lukas, INSTAAR
  36. 36. THE ‘LIST’ METHOD
  37. 37. S K E L E TO N P LOT T I N G
  38. 38. Photograph: Baillie (1982)
  39. 39. Ring width Tree age
  40. 40. Compare rings to their neighbors.
  41. 41. Marking tree-ring specimens for dating decade half-century century millennium
  42. 42. RING MEASUREMENT
  43. 43. Source: Hughes and Brown, 1992
  44. 44. Widespread drought caused narrow rings to form across the southwest USA during 1748 and 1750.Source: Kurt Kipfmueller
  45. 45. What kind of trees have rings that can bedated? • 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.
  46. 46. ‘Complacent’
  47. 47. ‘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.
  48. 48. ‘Sensitive’
  49. 49. ‘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.
  50. 50. Tucson AZ
  51. 51. PRE-WORK ASSIGNMENTBefore next class, try cross-dating online
  52. 52. h p://www.ltrr.arizona.edu/skeletonplot/introcrossdate.htm or google ‘LTRR skeleton plot’
  53. 53. P R I N C I P L E S O F C R O S S - DAT I N G

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