The dominant environmental driver of leaf water stable isotope enrichment differs for H-2 compared to O-18
Researcher:
Ferrio Díaz, Juan Pedro
Congress:
EGU General Assembly 2020
Participation type:
Otros
Other authors:
Matthias Cuntz, Lucas A Cernusak, Adrià Barbeta, Rebekka Bögelein, Rosemary T Bush, Juan Pedro Ferrio, Lawrence B Flanagan, Arthur Gessler, Paula Martín-Gómez, Regina Hirl, Ansgar Kahmen, Claudia Keitel, Chun-Ta Lai, Niels Munksgaard, Daniel B Nelson, Jérôme Ogée, John S Roden, Hans Schnyder, Steven Voelker, Lixin Wang, Hilary Stuart- Williams, Lisa Wingate, Wusheng Yu, Liangju Zhao
Year:
2020
Location:
VIenna, Austria
Publication:
Matthias Cuntz, Lucas A Cernusak, Adrià Barbeta, Rebekka Bögelein, Rosemary T Bush, Juan Pedro Ferrio, Lawrence B Flanagan, Arthur Gessler, Paula Martín-Gómez, Regina Hirl, Ansgar Kahmen, Claudia Keitel, Chun-Ta Lai, Niels Munksgaard, Daniel B Nelson, Jérôme Ogée, John S Roden, Hans Schnyder, Steven Voelker, Lixin Wang, Hilary Stuart- Williams, Lisa Wingate, Wusheng Yu, Liangju Zhao. The dominant environmental driver of leaf water stable isotope
enrichment differs for H-2 compared to O-18. In EGU General Assembly 2020
Several important isotopic biomarkers derive at least part of their signal from the stable isotope
composition of leaf water (e.g., leaf wax δ2H, cellulose δ2H and δ18O, lignin δ18O). In order to
interpret these isotopic proxies, it is therefore helpful to know which environmental variable most
strongly controls a given leaf water stable isotope signal. We collated observations of the stable
isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air
temperature and relative humidity, to test whether the dominant driver of leaf water 2H
concentration could differ from that of 18O concentration. Our dataset comprises 690 observations
from 35 sites with broad geographical coverage. We limited our analysis to daytime observations,
when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take
place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water
stable isotope composition for both δ2H (R2=0.86, p<0.001) and δ18O (R2=0.63, p<0.001). It showed
about 10% admixture of source water was caused by unenriched water pools such as leaf veins or
the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air
temperature, and the stable isotope compositions of source water and atmospheric vapour.
However, it is not possible to invert the Craig-Gordon equation to solve for one of these
parameters unless the others are known. Here we show that the two isotopic signals of δ2H and
δ18O are predominantly driven by different environmental variables: leaf water δ2H correlated
most strongly with the δ2H of source water (R2=0.68, p<0.001) and atmospheric vapour (R2=0.63,
p<0.001), whereas leaf water δ18O correlated most strongly with air relative humidity (R2=0.46,
p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of
the same environmental information, but carry distinct signals of different climate factors, with
crucial implications for the interpretation of downstream isotopic biomarkers.
Several important isotopic biomarkers derive at least part of their signal from the stable isotope
composition of leaf water (e.g., leaf wax δ2H, cellulose δ2H and δ18O, lignin δ18O). In order to
interpret these isotopic proxies, it is therefore helpful to know which environmental variable most
strongly controls a given leaf water stable isotope signal. We collated observations of the stable
isotope compositions of leaf water, xylem water, and atmospheric vapour, along with air
temperature and relative humidity, to test whether the dominant driver of leaf water 2H
concentration could differ from that of 18O concentration. Our dataset comprises 690 observations
from 35 sites with broad geographical coverage. We limited our analysis to daytime observations,
when the photosynthetic processes that incorporate the leaf water isotopic signal primarily take
place. The Craig-Gordon equation was generally a good predictor for daytime bulk leaf water
stable isotope composition for both δ2H (R2=0.86, p<0.001) and δ18O (R2=0.63, p<0.001). It showed
about 10% admixture of source water was caused by unenriched water pools such as leaf veins or
the Péclet effect. Solving the Craig-Gordon equation requires knowledge of relative humidity, air
temperature, and the stable isotope compositions of source water and atmospheric vapour.
However, it is not possible to invert the Craig-Gordon equation to solve for one of these
parameters unless the others are known. Here we show that the two isotopic signals of δ2H and
δ18O are predominantly driven by different environmental variables: leaf water δ2H correlated
most strongly with the δ2H of source water (R2=0.68, p<0.001) and atmospheric vapour (R2=0.63,
p<0.001), whereas leaf water δ18O correlated most strongly with air relative humidity (R2=0.46,
p<0.001). We conclude that these two isotopic signals of leaf water are not simply mirror images of
the same environmental information, but carry distinct signals of different climate factors, with
crucial implications for the interpretation of downstream isotopic biomarkers.