tree rings and drought on the canadian prairies

Tree Rings and DroughtPast drought on the Canadian Prairies

Scott St . GeorgeGeological Survey of Canada

Prairie tree-ring network, ca. 1996

3

Fort Dufferin, Manitoba

6

4,000 year-old river logs

Prairie tree-ring network

Eastern Rockies

Northern Saskatchewan

Southern Manitoba

Northwestern Ontario

4Characteristics ofPrairie tree rings

The tree-ring record of summer drought in the Canadian Prairies

Scott St. GeorgeDavid MekoMartin-Phillippe GirardinGlen MacDonaldErik Nielsen

Greg PedersonDavid SauchynJacques TardifEmma Watson

Submitted to the Journal of Climate, January 2008

Tree age

Photo: Tom Harlan

Bristlecone pine4,844 years

Source: OLDLIST

Photo: Peter Kelly

Eastern white cedar1,653 years

Source: OLDLIST

Eastern white pine290 years

Source: M. Girardin

Bur oak279 years

Photo: Greg Pederson

Limber pine846 years

Source: G. Pederson

Photo: julie & fanu16

Richard I of England

S. Alberta

N. Saskatchewan

S. Manitoba

NW Ontario

0 125 250 375 500

225

485

169

480

Years

Length of regional records

Seasonality

”

“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. A.E. Douglass

200

10

20

30

40

50

60

70

80

90

Autumn Winter Spring Summer Autumn

82

24

73

Site

sDominant seasonal signals

21

22

Source: Environment Canada, Adjusted Historical Canadian Climate Data, 1895 – 2006

Medicine Hat, Alberta

24

Effectiveness

Dendrohydrology works best where it’s

dry...

and not so well where it’s

wet

Ringwidth as a proxy for ‘Lethbridge’ PDSI

Ringwidth as a proxy for ‘Dryden’ PDSI

Uncertainty

755 m3/s847 m3/s809 m3/s770 m3/s823 m3/s787 m3/s901 m3/s840 m3/s

“Trees are not thermometers or raingauges.”

Keith Briffa and colleagues

Quantitative drought estimates

Quantitative drought estimates

Can we do better? Absolutely!

Photo: Emma Watson

38

Photo: New York Times

Focus on long-term drought

0%

25%

50%

75%

100%

Single Year 5-Year Average

43%60%

57%

40%

Expl

aine

d va

rian

ce

Courtesy Keith Lombardo

Measure other stuffWood chemistry

Stable isotopes

Wood density

Wood anatomy

Prairie tree rings

41

& drought

Photo: Monceau

web.mac.com/scottstgeorge