False rings in cottonwood ( Populus fremontii ): Tree-ring evidence for an intensification of drought in a semi-arid river system by kiyomi morino & dave meko LABORATORY OF TREE-RING RESEARCH THE 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

April July November stage water table ~growing season

April July November stage water table ~growing season

April July November stage water table ~growing season

groundwater s h a l l o w

April 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 Pedro River USA MEXICO Cananea Benson Tombstone Sierra Vista

* CHL gage * TMB gage 0 1 2 km    BCG CHM FRB N

BCG CHM FRB 1933 1947 1948

BCG CHM FRB 1945 1953 1967

BCG CHM FRB 2 % 18 % 5 %

BCG CHM FRB 0.31 0.57 0.39

drought at ungaged sites ?

1 Drought is increasing . riparian

CHL TMB ?

   RATE wet dry BCG CHM FRB CHL TMB

2 Drought is episodic . riparian

pTrees with FR CHM FRB CHG wet dry

 Develop and characterize false-ring chronologies. II. Identify hydroclimatic factors related to false-ring formation .

BCG CHM FRB 1933 1947 1948

7 < 1 + 6 >

pSummer (Jul – Aug) m 3 /s pFall (Sept – Oct) m 3 /s Winter (Nov – Mar) m 3 /s Low Flow (May – July) #days Annual (pJul – Jun) m 3 /s Mass ANN (pJul – Jun) m 3 /s Spring T (Mar – Apr) º C

pSummer (Jul – Aug) m 3 /s pFall (Sept – Oct) m 3 /s Winter (Nov – Mar) m 3 /s Low Flow (May – July) #days Annual (pJul – Jun) m 3 /s Mass ANN (pJul – Jun) m 3 /s Spring T (Mar – Apr) º C

Results…

model predictors significant FRB-II FRB-I CHM-II CHM-I BCG + LOFL, – MASS – ANN + LOFL + LOFL, – MASS none

model predictors significant FRB-II FRB-I CHM-II CHM-I BCG + LOFL, – MASS – ANN + LOFL + LOFL, – MASS none

Proportion of Trees with a False Ring FRB: ANN CHM: LOFL 1970 1980 1990 2000

Conclusions …

1 off-site gages false-ring formation

CHL TMB    BCG CHM FRB

2 hydrological forcing may be site specific .

vs    LOFL ANN CHL TMB BCG CHM FRB

   BCG CHM FRB

3 Drought is intensifying . riparian

 synchronicity

BCG CHM FRB 2 % 18 % 5 %

pTrees with FR CHM FRB CHG wet dry

any questions?