Nature's Footprint Science Brochure

NATURE’S FOOTPRINT T HE SC IE NC E OF T R E E R ING DAT ING

TABL E OF C ONTE NTS

21 A Connected World

08 The Science

03 The History

24 Contact & Info

11 The World of Dendro

06 Dendro Defined

THE

24 23

Dendrochronology is a technique invented and developed

22 21 20 19

during the 20th century originally by astronomer

A. E. DOUGLASS

18 17 16 15

when he

14 13

discovered a correlation between tree rings and the sunspot cycle.

12 11 10 09 08 07 06 05 04 03 02 01

Were does it all begin?

1937

Life always finds a way Growth from within

1894

24 23

Douglas establishes Laboratory of Tree-Ring Research at University of Arizona

22 21

Dendochronology is established by Douglas

20 19

Beginnings

18 The roots of time

17

Where there is a will there is a way The circle of life

16 15 14

Only time will tell...

Mother nature speaks

Introduction of the Principle of Uniformatism

13

1785

12 11 10 09 08

Nothing is nigh

07 06 05 04 03 02 01

In April 1918, Wissler asked Douglass whether or not it would be possible to assign relative dates to samples that couldn’t be dated absolutely. Although this information would not associate particular sites with exact years, it would reveal whether or not ruins were constructed within the same time period.

On May 22, 1919, Douglass informed Wissler that six specimens from Aztec Ruin, New Mexico were cut down within a two-year period, and estimated that samples from Pueblo Bonito in New Mexico were possibly 25 years older than those collected at Aztec Ruin. Upon receiving this news, Wissler was certain Douglass would make a crucial contribution to archaeology. Douglass continued comparing samples between the two sites and concluded Pueblo Bonito actually predated Aztec Ruin by 40 to 45 years. These findings led to realization that relative dating could be used on many of the other ruins in the Southwest.

DENDROCHRONOLOGY IS THE MEANS BY WHICH Scientific dating is based on the analysis of tree-ring growth patterns. This technique was invented and developed during the 20th century originally by the astronomer A. E. Douglass. He discovered a correlation between tree rings and the sunspot cycle, and then proceeded to found the discipline of dendrochronology, which is known as the method of dating wood by analyzing the growth ring pattern. Douglas started his discoveries in this field in 1894 when he was also working and performing research at the Lowell Observatory in Flagstaff, Arizona.

In 1916, Douglass began obtaining and analyzing archaeological samples first collected during an expedition to northwest New Mexico by the University of Colorado and the American Museum of Natural History.

24 23 22 21 20 19 18 17 16 15

Although promising steps had been made in solving the mystery of these ruins in the Southwest, in 1920, the American Museum of Natural History discontinued the funding of Douglass’s research. In order to continue his dendroarchaeological research, Douglass would have to find funding elsewhere.

Since Douglass’s famous discovery in the American Southwest, his dendroarchaeological techniques have been used to date structures around the world. Furthermore, dendrochronology has been applied in a number of ways. Currently, tree rings are being used to reconstruct an array of activity including: fire regimes, volcanic activity, hurricane activity, glacial movement, precipitation, mass movements, and hydrology. In many ways anthropologists, ecologists, geographers, and also geologists are able to analyze the past and predict future trends. All of this is possible thanks to the tree ring research achievements of A.E. Douglass.

14 13 12 11 10 09 08 07 06 05 04 03 02 01

DEFINED

DENDRO

24 23

Otherwise known as

“TREE-RING” DATING,

22 21 20

dendro-

19 18

chronology

17

is the scientific method of dating based on the analysis of

16 15 14 13 12

patterns of tree rings, also

11 10 09

known as growth rings.

08 07 06 05 04 03 02 01

The way dendrochronology works is relatively simple. As a tree grows, it puts on a new growth or tree-ring every year, just under the bark. Trees grow, and put on tree-rings, at different rates according to the weather in any given year: a wider ring in a favourable year and a narrower ring in an unfavourable year. As a result, over a long period of time (say 60 years or more) there will be a corresponding sequence of tree-rings giving a pattern of wider and narrower rings which reflect droughts, cold summers, etc. In effect, the span of years during which a tree has lived will be represented by a certain unique fingerprint, which can then be detected in other significant and also geographically-similar tree-ring chronologies.

UNTIL RELATIVELY RECENTLY, RADIOCARBON dating of wooden objects was the only known scientific method of dating wooden objects. Although in general it was always successful, dated produced would have a range of plus or minus 20 years at best, and at worst could span two centuries or more. And this only dated the actual rings sampled for C14 analysis; the tree may well have continued to live for decades or even a century or more afterwards.

In the 1970’s a new scientific method of dating buildings was developed in this country - dendrochronology. Here was the answer to the building historian’s dream, an absolute dating process accurate to a single year, if not the season the tree was felled. The potential of this in studying the development of timber-framing was quickly realised by one of the early pioneers of the science, Dr John Fletcher, who began to investigate the medieval buildings of the Oxford region between 1974 and 1986.

24 23 22 21 20 19

To obtain this fingerprint, a radial section of timber from the pith or centre of the tree out to the bark edge is required (see sampling procedures). Once prepared, they are then measured under a x10/x45 microscope using a travelling stage electronically displaying displacement to a precision of 0.01mm. Thus each ring or year is represented by its measurement which is arranged as a series of ringwidth indices within a data set, with the earliest ring being placed at the beginning of the series, and the latest or outermost ring concluding the data set.

It should be noted that, for a variety of reasons, tree-ring dating can not always be successfully applied. For example, timbers may be too fast-grown with fewer, complacent rings, or from slower grown trees with distorted ring sequences due to pollarding or other damage. In neither case are they generally datable. Most historic roofs and timber-framed buildings were made from oak, which is the most suitable species for successful tree-ring analysis. Although elm and beech can also be dated and matched with the oak chronologies, elm in particular can often contain distorted and fast-grown rings making routine dating at times difficult.

18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

THE

SCIENCE 24 23

Growth rings are the result of new growth in the

22 21 20

VASCULAR CAMBIUM,

19 18 17

a layer of cells near the bark that is classi-

16 15

fied as a lateral meristem. This growth in diameter

14 13 12 11 10

is known as secondary growth.

09 08 07 06 05 04 03 02 01

GROWTH RINGS, WHICH ARE ALSO REFERRED to as tree rings or annual rings, can be seen in a horizontal cross section cut through the trunk of a tree. Growth rings are the result of new growth in the vascular cambium, a layer of cells near the bark that is classified as a lateral meristem.

This growth in diameter is known as secondary growth. Visible rings result from the change in growth speed through the seasons of the year, thus one ring usually marks the passage of one year in the life of the tree. The rings are more visible in temperate zones, where the seasons differ more markedly.

24

The rings are more visible in temperate zones, where the seasons differ more markedly. Dendrochronology drills are one of many tools used to sample and determine growth ring counting.

23 22 21 20

The inner portion of the growth ring that is formed early in the growing season, when growth is comparatively rapid and is known as “early wood” or “spring wood” or even “late-spring wood”. The outer portion is the “late wood” and is denser.

“Early wood” is used in preference to “spring wood”, as the latter term may not correspond to that time of year in climates where early wood is formed in the early summer or in autumn, as in some Mediterranean species.

Timber core samples measure the width of annual growth rings. By taking samples from different sites and different strata within a particular region, researchers can build a comprehensive historical sequence that becomes a part of the scientific record; for example, ancient timbers found in buildings can be dated to give an indication of when the source tree was alive and growing, setting an upper limit on the age of the wood. Some genera of trees are more suitable than others for this type of analysis. Likewise, in areas where trees grew in marginal conditions such as aridity or semi-aridity, the techniques of dendrochronology are more consistent than in humid areas.

These tools have been important in archaeological dating of timbers of the cliff dwellings of Native Americans in the arid Southwest.

19 18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

23

22

21

20

19

18

17

16

15

14

13

12

“Early wood” is used in preference to “spring wood” as the latter term may not correspond to that time of year in climates where early wood is formed in the early summer or in autumn, as in some Mediterranean species.

The inner portion of a growth ring is formed early in the growing season, when growth has become comparatively rapid and is known as “early wood” or “spring wood” or also “late-spring wood”.

The outer portion is the “late wood” and is denser

24

11 10

09

08

07

06

05

04

03

02

01

WORLD OF

24

climatology

23 22 21

ecology

20 19

geomorphology

18 17

glaciology

16 15

archeology

14 13 12 11 10

entomology

09 08

pyrochronology

07 06 05

hydrology

04 03 02 01

24 23 22 21 20 19 18

DENDRO EXISTS MUCH LIKE NATURES GREAT

17

footprint. It is a powerful map and timeline which can connect the past, present, and in some ways even the future.

This has three main areas of application.

It can be applied in Paleoecology, where it is used to determine certain aspects of past ecologies (most prominently climate) like, for example, archaeology and the history of art and architecture. In this case, it is used to date old panel paintings on wood, buildings, etc. such as radiocarbon dating, where it is used to calibrate radiocarbon ages. In some areas of the world, it is possible to date wood back a few thousand years, or even many thousands of years. Currently, the maximum for any that are deamed fully anchored chronologies is a little over eleven-thousand years from present. In some areas of the world, it is possible to date wood back a few thousand years, or even many thousands.

Within even these general areas, there are even more specific areas where dendrochronology can provide insight into our world. This list, or “world of dendro,� is also continually growing.

16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

THE SCIENCE THAT USES TREE RINGS TO STUDY and date earth surface processes that may have created, altered, or shaped the landscape. For, example, it can be used in analyzing changes in tree growth patterns via tree rings to date a series of landslide events.

24 23 22 21 20 19 18 17 16 15 14 13 12

nature

11

sees

10 09

DENDRO

e

08

geomorphology

v

06 05

e

04

xt z aw o u ta z x z o u w z a u z w z a a h u o t z o u a u xw tlz hw w aa hah 03

ty l t t lt y lt l t t t l t a lt tt l ll t t lt t a l t lt tt l l t l tt tt t t tlt t l t l l lt t l t t tl ttt t t t t ltlt t tl ll t t t

t l ttl tt z

u

w z

z

t

z

u

ow

o zz o

u

t

ow

t

h h zh za o 02 oht ua haha u uz a o z z h h za zh uo oau ha aug h uow u ahw a o hz tu 01 h a h k oh o o z l u u t a u h hh aa h oaz o xu u a z a t u za h u zo uoazw zxzuh ag i w k a h o zx l o u n u t a ho s a t h zo xa uw za x z h ah ozuzx xu u w x u w a ha o u az uz o wx zz hw woz x zxu w a hahou xx

tt g l t

y

t a

r

07

THE SCIENCE THAT USES TREE RINGS TO STUDY past and present changes in wildfires. For example, dendropyrochronology can be used in dating the fire scars that are left in tree rings to then determine how often fires occurred in the past.

24

DENDRO

23 22

pyrochronology

21 20 19 18 17 16

in ashes

&

earth

Like

fire

the

15 14 13

wind

12 11

&

past

10

scars

09 08

wildfires

07 06 05 04 03 02 01

EA EN

O U DE R

US

NW TH A

AT

IS P

ERCEIVED

URF ACE

H

WH

LI

ID ES H

ANT S LAT

AT

L

YB

DE

IO

NB

AK L

OB V

WI

PE LL S

THE

T

ON

H

u

u

i

d

m

n c

a

z o

i

f

DENDRO

climatology

p

d

a

z

p

24 23 22 21

o

20

a

19 18

d

17 16 15 14 13

u

d

12 11 10 09 08 07 06

THE SCIENCE THAT USES TREE RINGS TO STUDY present climate and reconstruct past climate. For example, the process can be used in analyzing ring widths of trees to determine how much rainfall fell per year long before weather records were kept.

05 04 03 02 01

THE SCIENCE THAT USES TREE RINGS TO STUDY changes in river flow, surface runoff, and lake levels. Dendrohydrology can be used in dating when trees were inundated to determine the sequence of lake level changes over time.

24 23 22 21 20 19 18 17 16

There is no such thing as continuity without...

15 14 13 12

DENDRO

hydrology

11 10 09 08 07 06 05 04 03

...tracability

02 01

T H AT W E F I N D .

S CLUES BUT ALSO CLUE ..

T H AT C O N N E C T.

T H E PA S T I T I S N O T O N LY

T H E L AY E R S ,

WHEN WE PEEL BACK

THE FUTURE ...THE PRESENT TO

t

DENDRO

e

o

n

m o

y

EVEN THE SMALLEST OF I N S E C T S L E AV E THEIR UNIQUE MARK WITHIN THE

INTERCONN E C T E D N AT U R E OF OUR TREES AND THEIR TELLING FOOTPRINTS

l

g o

24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 09 08 07 06 05

THE SCIENCE THAT USES TREE RINGS TO STUDY the past dynamics of insect populations.

For example, dendroentomology can be used in dating the growth suppressions left in tree rings from the western spruce budworm outbreaks in the past.

04 03 02 01

DENDRO

ecology smoke

Be mindful of...

&

24

mirrors

23 22 21

20 19 18 17 16 15 14 13 12 11 10 09 08 07 06 05

THE SCIENCE THAT USES TREE RINGS TO STUDY factors that affect the earth’s many ecosystems. For example Dendroecology can be used in analyzing the effects of air pollution on tree growth through studying changes in ring widths over time.

04 03 02 01

CONNECTED

A WORLD

24 23

The physical world is connected in all facets, and trees exist as the natural

PILLARS OF TIME

22 21 20 19

on

18 17 16

our earth—standing as a powerful timeline of the past.

15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

THE NATURAL WORLD IS CONNECTED IN ALL facets. Trees are often used to make analogies about the past. Family trees, the tree of life, the idea of getting back to your roots. However, beyond the powerful imagery that trees give us to represent our history, trees exist as the natural pillars of time in our world and they stand as a powerful timeline about the past.

As mentioned in length, Dendrochronology is the scientific method of tree-ring dating. Americans first developed it in the early 20th century and now “dendro” is a common method of chronology that is used by scientists all over the world. Dendrochronology has become a fundamental tool in science, used in wide a varity of applications for reinforcing and expanding on the timelines of historical and ecological events in the past.

So, now we know how trees are dated, but what does that tell us exactly? “Virtually all societies used wood in some fashion, and so, that provides us with materials that we can tree-ring date, and that will give us precise years for when sites were occupied,” says Towner.

Dendrochronology can also reveal the origin of the wood on a site, and by knowing when and where human activity occurred, archaeologists have a much better context for trying to understand the past.

Just like the rings in a tree grow every year, scientists’ knowledge of the past grows with every addition to their master chronologies. Eventually, trees may tell a history even more ancient than our own.

But for now, this timeline gives shape to an extensive portion of our shared human past, without which we’d be like trees without their roots.

24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01

EV E

RY T H

IT

IC

AL

TH

AT

NA TU W RA E A

D

NA TU

RA L

CI TI

N

DI TE

F

DE

IT Y

AB

IT

RE

IS

TH

N CO

NA TU

V IC

T ION

AND CLAR

NH

S VO I C E S P E A R E’ K TU REFULLY FR S L O OM N A SO C A R S W E

MO T BU H E TD O

IN

ALONG WITH I TS I

RS

NEC

ELF

OF

TH

BS

E

ZE

SE

ITS

O

EN

OF

W

E

TA K

E

CA

FA T SU R HA T H E T W TH G A EA IN BEN OK D LO FIN E W

AN

Y, D L IN H IT

WE ARE AL L CO N

RIT

NS

U

FR

AG

ILE

T , BU

IT

SPE

AK

SW

I

WE ARE ALL CONNECTED...

IS C

IN

NAT U R A L C I T I Z E B S A N D U R A L W O R L D. A O F S HU NAT MA THE

, BU T

RE

NS MA D IN HU CTE AS NE .

D ON RL C O L W AL L E R

F E CO M E S F U L L C I ING IN LI RCLE

24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 09

COME VISIT THE DENDROCHRONOLOGY MUSEUM located in Northern California to experience, and learn more about the “world of dendro” and tree-ring dating

08 07 06 05

TO LEARN MORE ABOUT DENDRO PLEASE VISIT our website at www.knowdendro.edu

04 03 02

DESIGNED BY VINCENT TAM

01