Dendroecology is the study of tree rings to analyze interactions between trees and their environment over time. It provides long-term perspectives on ecosystem processes and dynamics that are difficult to observe directly. Reconstructing forest demography, growth patterns, and disturbance history from tree rings helps understand how climate affects ecosystems. However, tree-ring data have limitations like missing or fragmentary records, and past conditions may differ from present ones.

1. November 6
Dendroecology
Source: Whitney Crawford

2. Dendroecology is the use of tree-ring dating and analyses
to investigate events and processes involving
the interactions of organisms with their environment.

3. Source: William Ciesla

4. Western spruce budworm Choristoneura occidentalis Freeman

5. Wind-thrown red pine Quetico Provincial Park, Canada

6. ASSIGNED READING
Tom Swetnam and Peter Brown (2010), Climatic inferences
from dendroecological reconstructions. M.K. Hughes et al.
(eds.), Dendroclimatology, Developments in
Paleoenvironmental Research.

7. Why does Ecology
need dendroecology?

8. “ Many ecosystem processes, especially those affected
by climate changes, manifest themselves only over
longer time periods and broader spatial scales than
”
encompassed in typical ecological studies.
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

9. “ Understanding the dynamics of long-lived
organisms and ecosystems — and the role of
climate in controlling these dynamics —
”
requires decadal to centennial and
landscape- to regional-scale perspectives.
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

10. DENDROECOLOGY
Forest demography
Growth dynamics
Disturbance ecology

11. THE PRINCIPLE OF AGGREGATE TREE GROWTH
Rt = At + Ct + δD1t + δD2t + Et

12. Forest demography

13. Source: Dawn Hopkins Source: Kurt Kipfmueller

14. “ Ecologists have long recognized that time series of
tree births and deaths are of fundamental value for
understanding forest and woodland dynamics.
”
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

15. Source: Kurt Kipfmueller

16. 1500 1600 1700 1800 1900 2000

17. Tree recruitment dates (by 50-year periods)
1500 1600 1700 1800 1900 2000

18. Tree mortality dates (by 50-year periods)
1500 1600 1700 1800 1900 2000

19. Pinyon Demography at Sevilleta LTER, Central New Mexico
Source: Betancourt et al. (2004)

20. Sampling dead trees in the pinon-juniper woodlands Tom Swetnam

21. COMPLICATING FACTORS

22. The condition of dead trees affects the continuity of their record.
Photograph: John Krumm

23. Snags may have lost an unknown number of outer rings.

24. TREE
DOES
NOT DATE OF
EQUAL GERMINATION
RECRUITMENT

25. Hi ing the pith is easy when you collect an entire cross-section.

26. It’s more difficult when coring, especially if growth is asymmetric.

27. Coring height
Root collar
How many years separate the root collar from the stem at coring height?

28. The germination date can be MUCH earlier than tree age at coring height.
Source: Gutsell and Johnston (2002)

30. Source: Kurt Kipfmueller
Germination doesn’t happen immediately a er disturbance.

31. The ecesis interval is the amount of time between
an initial disturbance and the successful establishment
of the first trees.

32. THE
‘FADING RECORD’
PROBLEM
The preservation of dead trees becomes less common with time
before present, and obtaining estimates of past mortality events
depends both on persistence of woody material and the ability to
adequately sample the material to obtain death dates.

33. How can we reduce the effects
of these different sources of uncertainty?

34. “ In old, uneven-aged forests, sometimes hundreds
of trees must be sampled to obtain adequate
characterization of age structure distributions.
”
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

36. Source: Dawn Hopkins Source: Kurt Kipfmueller

37. Source: Swetnam and Brown (2010)
Germination pulses of ponderosa pine have coincided with warm, wet summers.

38. Growth dynamics
Source: Kyle Pierce

39. Growth releases may be caused by the death of ‘overstory’ trees.

42. A growth release is the opposite of a suppression,
with growth increasing rapidly for several years.

43. A growth suppression is a rapid reduction of growth
from one year to the next, usually lasting for several years.

44. Source: Fri s and Swetnam, 1989
Growth release caused by 1966 timber harvest.

45. Source: Eli Sagor
Growth suppressions are caused commonly by defoliating insects.

46. Source: Fri s and Swetnam, 1989
Suppression, possibly caused by A.D. 1064 eruption at Sunset Crater in Arizona.

47. Source: Berg et al. (2006)
Release events can be used to identify past insect outbreaks.

48. Source: Berg et al. (2006)
You really need to study the frequency of releases across MANY stands.

49. Disturbance ecology
Source: Miguel Vieira

50. THE PRINCIPLE OF AGGREGATE TREE GROWTH
Rt = At + Ct + δD1t + δD2t + Et

51. Western spruce budworm Choristoneura occidentalis Freeman

52. Source: brewbooks
White fir Abies concolor

53. Douglas-fir Pseudotsuga menziesii

54. Source: William Ciesla

55. Source: William Ciesla

56. “ No typical pa ern or trend in western spruce
budworm epidemics has been apparent; most of
the early epidemics lasted for a few years and
”
then subsided naturally; others persisted longer,
at times without spreading over large areas.
David Fellin and Jerald Dewey
Western Spruce Budworm, 1982

57. Source: Dave Powell

58. HOST NON-hOST

59. “ The tree-ring basis for developing outbreak
chronologies is the observation of very sharply
reduced ring growth in the host species during
”
the defoliation episode, which typically lasts for
a decade or longer.
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

60. Western spruce budworm Choristoneura occidentalis Freeman

61. Source: Brewbooks

62. HOST NON-hOST
White fir
Ponderosa Pine
Douglas-fir

63. Source: Tom Swetnam
Growth suppression in white fir defoliated by spruce budworm

64. THE PRINCIPLE OF AGGREGATE TREE GROWTH
Rt = At + Ct + δD1t + δD2t + Et

65. G(HOST) < G(NON-HOST)
=
potential outbreak

66. Source: Ryerson et al. (2003)

67. Comparisons between hosts and non-hosts can help
identify budworm outbreaks
BLACK = Host < Non-host GRAY = Host > Non-host
Source: Ryerson et al. (2003)

68. Percentage of trees recording an outbreak of western spruce budworm in the Rio Grande National Forest, Colorado
Source: Ryerson et al. (2003)

69. “ In old, uneven-aged forests, sometimes hundreds
of trees must be sampled to obtain adequate
characterization of age structure distributions.
”
Tom Swetnam and Peter Brown
Dendroclimatology, 2010

70. Do drought conditions inhibit spruce budworm outbreaks?
Source: Ryerson et al. (2003)

71. November 6
Dendroecology
Source: Whitney Crawford

72. Strengths of dendroecology
1. Tree-ring records provide a much longer perspective
than documentary records or modern surveys.
2. Tree-ring evidence has a high degree of temporal
precision compared to other paleoecological tools.
3. Chronological control allows multiple lines of
evidence to be compared.

73. Limitations of dendroecology
1. Tree-ring records are fragmentary and can be
distributed irregularly in time and space.
2. Some species, events or processes cannot be
reconstructed and therefore remain unknown.
3. Past ecological conditions may have no analog in
the modern system, making their behavior difficult
to interpret.

74. GEOG8280
XT C L AS S
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