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?