False rings in cottonwood (Populus fremontii): Tree-ring evidence for an intensification of drought in a semi-

arid river system

by kiyomi morino & dave mekoLABORATORY OF TREE-RING RESEARCHTHE UNIVERSITY OF ARIZONA, TUCSON

AmeriDendro 2008, UBC

dendro-flavor?

hydrology

NOT your mother’s dendro-hydrology

3…

ring

widths

<cottonwood false ring>

bark

FALSE RING

1 growing season

CHL TMB

?

“ ”hydrologic

connectivity

“ ”drought

60 90 120 150 180 210 240 270 300 330 360

Ele

vatio

n (m

)

1189.0

1189.5

1190.0

1190.5

1191.0

1191.5

1192.0April July November

stage

water table

~growing season

60 90 120 150 180 210 240 270 300 330 360

Ele

vatio

n (m

)

1189.0

1189.5

1190.0

1190.5

1191.0

1191.5

1192.0April July November

stage

water table

~growing season

60 90 120 150 180 210 240 270 300 330 360

Ele

vatio

n (m

)

1189.0

1189.5

1190.0

1190.5

1191.0

1191.5

1192.0April July November

stage

water table

~growing season

groundwaters h a l l o w

60 90 120 150 180 210 240 270 300 330 360

Ele

vatio

n (m

)

1189.0

1189.5

1190.0

1190.5

1191.0

1191.5

1192.0April July November

stage

water table

~growing season

I. Develop and characterize false-ring chronologies.

II. Identify hydroclimatic factors related to false-ring formation.

Phoenix

ARIZONA

SONORA

Tucson

Hermosillo

0 50 km

San Pe

dro

Rive

r

USAMEXICO

Cananea

Benson

Tombstone

Sierra Vista

0 1 2 km

BCG

CHM

FRB

N

*CHL gage

*TMB gage

1930 1940 1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

1933

1947

1948

Pro

port

ion

of T

rees

with

a F

alse

Rin

g

0.00

0.25

0.50

0.75

1.00

1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

1945

1953

1967

Pro

port

ion

of T

rees

with

a F

alse

Rin

g

0.00

0.25

0.50

0.75

1.00

1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

2%

18%

5%

Pro

port

ion

of T

rees

with

a F

alse

Rin

g

0.00

0.25

0.50

0.75

1.00

1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

0.31

0.57

0.39

drought at ungaged sites?

1Drought is increasing.

riparian

CHL TMB

?

RA

TE

wet dry

BCG

CHMFRB

CHL TMB

2Drought is episodic.

riparian

pTre

es

wit

h F

R

1950 1960 1970 1980 1990 20000.00

0.25

0.50

0.75

1.00

CHMFRB

CHG wet

dry

Develop and characterize false-ring chronologies.II. Identify hydroclimatic

factors related to false-ring formation.

1930 1940 1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

1933

1947

1948

7<1 + 6>

pSummer (Jul – Aug) m3/s

pFall (Sept – Oct) m3/s

Winter (Nov – Mar) m3/s

Low Flow (May – July) #days

Annual (pJul – Jun) m3/s

MassANN (pJul – Jun) m3/s

Spring T (Mar – Apr) ºC

pSummer (Jul – Aug) m3/s

pFall (Sept – Oct) m3/s

Winter (Nov – Mar) m3/s

Low Flow (May – July) #days

Annual (pJul – Jun) m3/s

MassANN (pJul – Jun) m3/s

Spring T (Mar – Apr) ºC

Results…

BCG none

CHM-I + LOFL, – MASS

CHM-II + LOFL

FRB-I – ANN

FRB-II + LOFL, – MASS

model predictorssignificant

BCG none

CHM-I + LOFL, – MASS

CHM-II + LOFL

FRB-I – ANN

FRB-II + LOFL, – MASS

model predictorssignificant

Pro

port

ion

of

Tre

es

wit

h a

Fals

e R

ing

FRB: ANN

CHM: LOFL

1970 1980 1990 2000

Conclusions …

1off-site gages

false-ring formation

CHL TMB

BCG CHM FRB

2hydrological forcing may be site specific.

vs

LOFLANN

CHL TMB

BCG CHM FRB

BCG CHM FRB

3Drought is intensifying.

riparian

synchronicity

Pro

port

ion

of T

rees

with

a F

alse

Rin

g

0.00

0.25

0.50

0.75

1.00

1950 1960 1970 1980 1990 2000

BCG

CHM

FRB

2%

18%

5%

pTre

es

wit

h F

R

1950 1960 1970 1980 1990 20000.00

0.25

0.50

0.75

1.00

CHMFRB

CHG wet

dry

anyquestions?