What archeologists need to know about dendrochronology in Minnesota

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