Griessinger, J., Bräuning, A.,
Helle, G., Schlesser, G.H.,
Hochreuther, P., Meier, W. J.-H.
and Zhu, H.
2019
"A dual stable isotope approach
unravels common climate signals
and species-specific responses
to environmental change
stored in multi-century
tree-ring series from the
Tibetan Plateau."
Geosciences 9: 151;
doi:10.3390/geosciences9040151
NOTE:
Many studies show plants
produce a greater amount
of biomass per unit of water,
at higher atmospheric
CO2 concentrations,
than at lower ones.
Few studies documented
the long term effects
out in the real world of nature,
before Griessinger et al. (2019).
SUMMARY:
The seven-member research team
calculated the intrinsic
water use efficiency (iWUE),
defined as the ratio of
net photosynthetic assimilation
rate to stomatal conductance
for water vapor, of juniper
(Juniperus tibetica)
and spruce trees
(Picea balfouriana)
growing at a
high mountain site
on the southeastern
Tibetan Plateau.
Griessinger et al. (2019)
add to the growing body
of literature demonstrating
real-world evidence of what
short-term laboratory
and field experimental
studies have concluded,
that rising atmospheric CO2
increases plant
water use efficiency.
And that's
good news
for plants growing
in arid regions
where water is
a limiting
growth factor.
DETAILS:
There was little
long-term change
in iWUE over the first half
of the 20th century,
when atmospheric CO2
concentrations rose by
only +11 ppm.
During the second half
of the 20th century,
through the end
of their record in 2007,
the CO2 concentration
rose by a much larger
+72 ppm, which did
impact iWUE.
For spruce trees,
the increase in iWUE
over this recent interval
amounted to +14%,
for juniper it was + 20%.
Griessinger et al.
say they are
"in good accordance
to existing studies
from the Tibetan Plateau
dealing with Pinus and
Abies species, where
similar positive trends in iWUE
were reported
for the last decades,"
citing the works
of Xu et al. (2013)
and Huang et al. (2017).
REFERENCES:
Huang, R., Zhu, H., Liu, X., Liang, E., Griessinger, J., Wu, G., Li, X. and Bräuning, A. 2017. Does increasing intrinsic water use efficiency (iWUE) stimulate tree growth at natural timberline on the southeastern Tibetan plateau? Global and Planetary Change 148: 217-226.
Xu, G., Liu, X., Qin, D., Chen, T., An,W., Wang,W., Wu, G., Zeng, X. and Ren, J. 2013. Climate warming and increasing atmospheric CO2 have contributed to increased water use efficiency on the northeastern Tibetan plateau since 1850. Trees 27: 465-475.