Upload
scott-st-george
View
572
Download
1
Embed Size (px)
Citation preview
Doctor of PhilosophyUniversity of Arizona
Master of ScienceUniversity of Western Ontario
Bachelor of ScienceUniversity of Winnipeg
Source: Dave Sauchyn
Genesis 41, 29-30
Behold, there comes seven years of great plenty throughout all the land of Egypt: And there shall arise a!er them seven years of famine; and all the plenty shall be forgo"en in the land of Egypt; and the famine shall consume the land;
ENVIRONMENTAL HISTORY
Tree-ring display at elementary school
Source: Tom Swetnam
MUCH MORETHAN JUST
COUNTING TREE RINGS.
DENDROCHRONOLOGY IS
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
Andrew Douglass University of Arizona
Crossdating is the recognition of the same ring pa"ern in di#erent trees, so that the actual growth date of any one ring of the pa"ern is the same in the di#erent trees and one may carry a chronology across from tree to tree.
“ ”A.E. Douglass
Journal of Forestry, 1941
Pueblo Bonito New Mexico (before it was excavated)
Source: Stones 55
Source: mlhradio
Source: Alan Stark
Tree-ring display at elementary school
Photograph: Tom Swetnam
Tree-ring analysis is one of the most powerful tools available for the study of environmental change and the identification of fundamental relationships between tree growth and climate.“ ”
Edward Cook and Neil PedersonUncertainty, Emergence, and Statistics in Dendrochronology
DENDRO-WHAT ARCHEOLOGISTSNEED TO KNOW ABOUT
IN MINNESOTACHRONOLOGY
How old is the oldest tree in Minnesota?
Source: Ralph Sievert
The Seward oak 330 yr?
Source: Joe Zeleznik NDSU
Bur oak >450 yr
White pine 1714
Source: Kurt Kipfmueller
Source: Danny Margoles
White cedar 1452
Source: Robert Simon, NASA and the Woods Hole Research Center
Source: Jonathan Frazier
Source: Erik Nielsen
42
Source: Erik Nielsen
Source: Baillie (1982)
Dating wood artifacts
APPLICATION
Source: Pearce Paul Creasman
‘Rat River’ House 1859
Source: Erik Nielsen
THREEMAIN REQUIREMENTS
FOR TREE-RING DATINGWOOD ARTIFACTS
1 Specimens should have enough rings to describe the unique sequence of growth (generally, more than 80 years).
2 The ring sequence should exhibit a high degree of year-to-year variability (in other words, each ring should not look like every other ring).
3 The artifact should have been constructed from local trees, with the wood transported not more than a few hundred kilometers from its cu"ing location.
Dugout canoe McLoud County Historical Museum, Minnesota
climate
Reconstructing past droughts
APPLICATION
“The growth of trees is undoubtably controlled more by the movement of water than by the movement of any other single substance.”
Hal Fri!sTree Rings and Climate
water stress
reduced cell division
less cell expansion
reduced photosynthesisnarrow ring
Drought severityWeather measurements
Estimated from tree rings
Source: St. George et al., Journal of Climate, 2009
Tree rings provide the long perspective on drought severity
Cook et al., 2007, Earth Science Reviews
NORTH AMERICANDROUGHT ATLAS
Tree-ring estimates of summer drought across North America
AD 1452
Source: Cook and Krusic, 2004
St. George et al., The Holocene, 2010
Drought (and tree growth) can be ‘tuned’ to di"erent seasons
climate
Understanding natural hazards
APPLICATION
climate
ecology
climate
forest dynamics
landscape change
floods
AP Photo/U.S. Coast Guard, Lt. Brendan Evans
69
St.. George and Nielsen, The Holocene, 2003
Source: Lane Johnson
Source: Lane Johnson
1875
1653
MUCH MORETHAN JUST
COUNTING TREE RINGS.
DENDROCHRONOLOGY IS
Photo: Calvin FerrisKurt Kipfmueller University of Minnesota
How has climate and human activity a#ected forest fires in the Boundary Waters?
How o!en do severe floods occur on the Red River, and why?
How is the snowpack in the central Rockies changing?
How has the hydrology of Lake Winnipeg changed during the late Holocene?
Does decadal climate variability a#ect forest ecology and wildfire risks?
CURRENT PROJECTS
I N T R O D U C T I O N T O D E N D R O C H R O N O L O G Y
C L I M A T E V A R I A T I O N S
National Geographic ‘Beam Expeditions’ 1920s
Social Sciences Tower