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Tree rings and drought on the Canadian Prairies
I've been asked to give a presentation at a workshop to be held in Alberta in March. The workshop will revolve mainly around the use of tree rings and other natural 'proxy' records to water issues in the Canadian Prairie provinces.
I'll be presenting material drawn from the last chapter of my doctoral dissertation, and will talk about the strengths and limitations of tree-ring records as indicators of past drought. The audience will include between 50 and 100 water managers from the region, and for many of them, the workshop will be their first exposure to tree rings and other forms of paleoclimatology. I think it will be in their best interest (and mine) that the scientific presentations focus more on big-picture ideas and less on technical details and methodology.
With an eye towards getting my point across more effectively, I've worked up a set of slides in the 'Presentation Zen' style. I've included more photos than I have in previous presentations, and have also tried to swap out complex journal-style diagrams and replace them with simpler graphics.
I'm excited (and a little nervous) to see how the presentation is received - I imagine its style will be quite different from the other talks in the workshop. I've posted the slides at Slideshare.net, and would appreciate any comments or suggestions - the workshop is not for another six weeks, so I have plenty of time left to tweak or change my plans.
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Slideshow Transcript
- Slide 1: Tree Rings and Drought
Past drought on the Canadian Prairies
S co tt St. Ge orge
Geological Survey of Canada
- Slide 2: Prairie tree-ring network, ca. 1996
- Slide 3: 3
- Slide 5: Fort Dufferin, Manitoba
- Slide 6: 4,000 year-old
river logs
6
- Slide 7: Prairie tree-ring network
Northern Saskatchewan
Eastern Rockies
Northwestern
Ontario
Southern Manitoba
- Slide 8: 4
Characteristics of
Prairie tree rings
- Slide 9: The tree-ring record of summer
drought in the Canadian Prairies
Scott St. George
David Meko Greg Pederson
Martin-Phillippe Girardin David Sauchyn
Glen MacDonald Jacques Tardif
Erik Nielsen Emma Watson
Submitted to the Journal of Climate, January 2008
- Slide 10: Tree age
- Slide 11: Bristlecone pine
4,844 years
Source: OLDLIST
Photo: Tom Harlan
- Slide 12: Eastern white cedar
1,653 years
Source: OLDLIST
Photo: Peter Kelly
- Slide 13: Eastern white pine
290 years
Source: M. Girardin
- Slide 14: Bur oak
279 years
- Slide 15: Limber pine
846 years
Source: G. Pederson
Photo: Greg Pederson
- Slide 16: Richard I of England 16
Photo: julie & fanu
- Slide 17: Length of regional records
S. Alberta 480
N. Saskatchewan 169
S. Manitoba 485
NW Ontario 225
0 125 250 375 500
Years
- Slide 18: Seasonality
- Slide 19: “
The trees composing the
forest rejoice and lament with
its successes and failures and
carry year by year something
of its story in their annual
rings.
”Douglass
A.E.
- Slide 20: Dominant seasonal signals
90
82
80
70
60
50
Sites
40
30 24
20
10 7
3
0 20
Autumn Winter Spring Summer Autumn
- Slide 21: 21
- Slide 22: 22
- Slide 23: Medicine Hat, Alberta
Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006
- Slide 24: 24
- Slide 25: Effectiveness
- Slide 26: Dendrohydrology
works best where it’s
dry ...
- Slide 27: and not so well
where it’s
wet
- Slide 28: Ringwidth as a proxy for
‘Lethbridge’ PDSI
- Slide 29: Ringwidth as a proxy for
‘Dryden’ PDSI
- Slide 30: Uncertainty
- Slide 31: 755 m3/s
847 m3/s
809 m3/s
770 m3/s
823 m3/s
787 m3/s
901 m3/s
3
- Slide 32: “Trees are not thermometers
or raingauges.”
Keith Briffa and colleagues
- Slide 33: Quantitative drought estimates
- Slide 34: Quantitative drought estimates
- Slide 35: Can we
Absolutely!
do better?
- Slide 36: Photo: Emma Watson
- Slide 38: Photo: New York Times
38
- Slide 39: Focus on long-term drought
100% 60% 43%
Explained variance
75%
50% 57%
40%
25%
0%
Single Year 5-Year Average
- Slide 40: Courtesy Keith Lombardo
Measure other stuff
Wood chemistry Wood density
Stable isotopes Wood anatomy
- Slide 41: Prairie tree rings
& drought
41
- Slide 42: Photo: Monceau
web.mac.com/scottstgeorge