Wang, H., Zhou, G.,
Jiang, Y., Shi, Y.
and Xu, Z.
2019
Effects of
elevated CO2
on Stipa baicalensis
photosynthesis
depend on
the precipitation
and growth phase.
Ecological Research 34: 790-801.
NOTE:
Stipa baicalensis is
a C3 perennial bunch grass
dominant throughout
the Songnen Plain and
Inner Mongolian Plateau
of China.
Domestic livestock feed
on it thanks to its good
palatability and high
forage value.
Wang et al. (2019) stated:
"studies in S. baicalensis
response to both elevated CO2
and varying precipitation are rare."
SUMMARY:
Wang et al. conclude
"the elevated CO2
concentration in the future
might be beneficial
to the growth of
S. baicalensis," .
The positive influence
will be dependent on
"precipitation conditions
and the growth phase".
DETAILS:
Working in an open-top
chamber environment,
Wang et al. subjected
S. baicalensis samples
to ambient (390 ppm)
or elevated (550 ppm)
levels of atmospheric CO2
and one of five
precipitation regimes.
The goal was to determine
the combined impacts
of these two variables
on S. baicalensis
productivity,
water use efficiency
and biomass.
The five
precipitation regimes
included a control,
set to the 30-year monthly
precipitation average
for both June and August,
and values that were
15% and 30% above
and below the 30 year
monthly averages
for each of these
two months.
The results of their study
are displayed in the
two figures below.
Figure 1
Elevated CO2 raised plant
net photosynthesis
in every precipitation
treatment in each month
(from 3-70% in June
and from 13-52% in August),
with the greatest values
for net photosynthesis
being observed during
the height of summer in August.
Plant water use efficiency
was significantly higher
in August in all watering
treatments under elevated CO2,
whereas in June
it was only higher
in the control and
-15% precipitation
treatments,
approximately equal
in the -30% and +30%
precipitation treatments,
and lower in the
+15% treatment.
Relative differences
observed between
June and August may
well have been impacted
by plant age
(grass cultivated
in June were relatively
young compared to that
cultivated in August,
which were completely
mature).
Figure 2 indicates
this parameter
was enhanced
by approximately
48%, 100%, 58%, 53%
and 21% under
elevated CO2 conditions
in the -30%, -15%, control,
+15% and +30%
precipitation treatments.
