A Dendrochronological Reconstruction of Western Spruce Budworm Outbreaks in the South Okanagan Valley, Canada

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A Dendrochronological Reconstruction of Western
Spruce Budworm Outbreaks in the South Okanagan
Valley, Canada

• By Team Ogopogo

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Background

• Insect outbreaks are a major disturbance in
  forests of Western North America
• Douglas-fir (Pseudotsuga menziesii) is a host for
  western spruce budworm (WSB Choristoneura
  occidentalis Freeman)
• From 1972-2001, spruce budworm outbreaks affected
  100,000 ha of Douglas-fir forest in the South
  Okanagan Valley

Canadian Forest Service
B.C. Ministry of Forests
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Study Site
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Western Spruce Budworm Outbreaks

• gt2000 Endemic
• 1999 Severe
• 1998 Severe
• 1994 Moderate
• 1992 Moderate
• 1991 Severe
• 1990 Moderate
• 1989 Low
• 1988 Low
• 1987 Low

Low
Moderate
Severe
By FIDS, Nealis et al. unpublished
B.C. Ministry of Forests
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Background

• Douglas-fir (host) growth is affected by WSB
• Ponderosa pine (Pinus ponderosae) is a non-host
  for WSB
• Ponderosa pine can be used as a control

From Burleigh et al.2002
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Research Questions

1. Can we reconstruct outbreaks of WSB prior to 1950
   using tree rings?
2. When did the outbreaks of WSB occur, and what is
   the frequency, duration, and intensity of
   outbreaks?
3. Is there a relationship between climate and
   outbreaks?

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Host Site

• Dominated by Douglas-fir a WSB host
• 3 transects parallel to slope (lower, mid, and
  higher elevation)
• For each transect, selectively cored 10 live
  mature trees (2 cores/tree) at 30 cm height

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(No Transcript)
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Host Site

• Noted pathological indicators (top kill,
  resprout, fire scars, and mistletoe)
• Avoided heavily infested areas
• Obtained cross sections of 2 fallen trees (one
  with fire scars)

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Non-host Site

• Ponderosa pine a WSB non-host
• Randomly selected 23 mature and healthy trees to
  core (2 cores/tree) at lower, mid, and higher
  elevation

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Laboratory Methods

• Cores mounted and sanded with increasingly
  finer-grit sandpaper (120-600)
• Tree rings measured with Velmex measuring stage
• Measured cross-sections using WinDendro

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Laboratory Methods

• Cross dated using skeleton plots and list method
• Quality control of cross dating statistically
  confirmed with software program COFECHA

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Analysis

• Removed age-related growth with ARSTAN (negative
  exponential curve for host and 32-year cubic
  smoothing spline for non-host)

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Analysis

• Identified potential WSB defoliations (i.e.,
  suppressions) on standardized individual tree
  ring series for host and non-standardized
  tree-ring chronology for non-host using OUTBREAK

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Analysis

• Used published literature for WSB outbreaks in
  the area
• Threshold 1.28 SD
• Duration 8 years
• Used sensitivity analysis and settled on
• Threshold 1.32 SD
• Duration 8 years
• Jonathan will explain spectral analysis

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Results and Discussion
Host Douglas-fir Non-host ponderosa pine
dated of series 64 23
Master series 1619-2008 1805-2007
Series intercorrelation 0.642 0.523
Mean sensitivity 0.269 0.272
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Host
Non-host
Outbreaks
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Peak outbreak
Recovery period
Outbreak period
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Outbreak N Outbreak period Duration (years) Recovery period Duration (years) Peak outbreak Period between peaks
1 1825-1835 11 1836-1841 6 1834-1835  
2 1850-1858 9 1859-1861 3 1858 23
3 1878-1880 3 1881-1885 5 1880 22
4 1900-1906 7 1907-1909 3 1903-1906 26
5 1918-1924 7 1925-1930 6 1924 18
6 1932-1942 11 1943-1948 6 1938-1942 18
7 1975-1976 2 1977-1979 3 1975-1976 34
8 1990-1997 8 1998-2003 6 1996-1997 21
  X 6.7  X 4.6  X 23.2
  Std Dev 3.2 Std Dev 1.5 Std Dev 6.1
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• Significant cycles
• Are some cycles related to WSB outbreaks?

• How do these cycles vary over time?
• This is how the signal looks like

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• Is there any cycles in the WSB outbreak history?
• Cyclic variability (again!)
• Decadal and inter-decadal variability in
  outbreaks

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Summary and Conclusions

• Douglas-fir tree rings can be used to reconstruct
  outbreaks of WSB prior to 1950.
• WSB outbreaks
• Outbreaks 8 (including 6 undocumented pre-1950)
• Average frequency 23.2 years
• Average duration 6.7 years
• Average intensity 43 of trees
• Is there a relationship between climate and WSB
  outbreaks?
• Ask René!

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Acknowledgements

• Team Ogopogo would like to thank these funding
  agencies National Science Foundation, Canadian
  Forest Service Pacific Forestry Centre,
  University of Northern British Columbia Tree Ring
  Laboratory, University of British Columbia Tree
  Ring Laboratory, Indiana State University
  Dendrochronology Laboratory, University of
  Tennessee Laboratory of Tree Ring Science,
  University of Guelph , University of Victoria,
  British Columbia Forest Service, and US Forest
  Service Rocky Mountain Research Station. We
  thank the Double Diamond Hostel, and the Gun
  Barrel Saloon for providing support and
  accommodations during this fieldweek.

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Team Ogopogo
Baileys chocolate
Have you seen René?
Kathy
Kevin
Jonathan
Hugo
Laurel
Maria Laura
Jodi
Claudia
Lidio
Maria Paz
Eileen
Lara
zzzzzzzzzz