The document discusses the principle of cross-dating tree rings. [1] Cross-dating involves matching patterns in tree ring widths or characteristics among multiple trees to identify the exact year each ring was formed. [2] This allows scientists to synchronize the tree ring chronologies and date wood samples far into the past without relying solely on ring counting. [3] Cross-dating is essential for dendrochronology because of various complications that can occur with tree ring formation.

1. September 20
The principle of cross-dating
Source: Baillie (1982)

2. GEOG5839
FROM LIMITS TO PATTERNS

3. h p://esp.cr.usgs.gov/data/atlas/li le/

4. Isolated populations
**
x *
MAIN RANGE DISCONTINUOUS TEMPORARY
RANGE POPULATIONS
*
*
x ** Individual adults
x populations
Extinct
(not reproducing)

5. h p://esp.cr.usgs.gov/data/atlas/li le/

6. Source: Elroy

7. Source: Bryant Olsen

8. Source: Phil Camill

9. THE LAW OF THE MINIMUM
Growth is controlled by the scarcest resource
(limiting factor), not the total amount of
resources available

10. Average temperatures are remarkably consistent at treeline locations around the world.
Source: Körner and Paulsen, Journal of Biogeography, 2004

11. temperature water day length

12. h p://esp.cr.usgs.gov/data/atlas/li le/

13. “COMPLACENT”

14. “SENSITIVE”

15. Weather and climate act to synchronize growth rates
at the level of the cell, the tree, the forest and beyond.

16. “ RINGS ”
IN THE BRANCHES OF
SAWED TREES SHOW
THE NUMBER OF YEARS
AND, ACCORDING TO THEIR
THICKNESS,
THE YEARS WHICH WERE
MORE OR LESS
DRY.
Leonardo da Vinci

17. Tree-ring width is not just a
function of wet and dry

21. Same environmental forcings
Similar
growth pa erns

22. GEOG5839
CHRONOLOGY

23. THE PRINCIPLE OF CROSS-DATING
Matching pa erns in tree-ring widths or other ring characteristics
(such as ring density) among several trees allow the identification
of the exact year in which each ring was formed.

25. Photograph: Dan Griffin

28. 3
Different approaches

29. THE ‘LIST’ METHOD

30. THE PRINCIPLE OF CROSS-DATING
1900 1910 1920 1930
Two Douglas-fir cores from Eldorado Canyon, CO
Source: Jeff Lukas, INSTAAR

32. SKELETON PLOTTING

34. Compare rings to their neighbors.

35. RING MEASUREMENT

36. Source: Hughes and Brown, 1992

38. GEOG5839
PROBLEMS WITH DATING

39. Why can’t you just count the rings back in time?

40. COMPLICATION #1
“Micro” rings

41. Ponderosa pine
Pinus ponderosa
Source: Peter Brown

42. COMPLICATION #2
Partial rings

43. Limber pine
Pinus flexilis

44. COMPLICATION #3
Missing rings

45. Picture not available.

46. 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.

47. COMPLICATION #4
False rings

48. Ponderosa pine
Pinus ponderosa
Source: Peter Brown

49. Arizona cypress
Cupressus arizonica
Source: Peter Brown

50. False
ring boundary
sharp
gradual
Annual
ring boundary

51. Why can’t you just count the rings back in time?

52. GEOG5839
PUZZLES IN TIME

54. Widespread drought caused narrow rings
to form across the southwest USA
during 1748 and 1750.
Source: Kurt Kipfmueller

56. COMPLICATION #5
No outer date

57. 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.

59. Photo: Erik Nielsen

60. 68
Photo: Erik Nielsen

61. 69

63. 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.

66. ‘Complacent’

67. ‘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.

68. Tucson AZ

71. ‘Sensitive’

72. ‘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.

73. September 20
The principle of cross-dating
Source: Baillie (1982)

76. GEOG8280
XT C L AS S
NE