Lu, K., Chen, N., Zhang, X.,
Wang, J., Wang, M., Khan, S.,
Han, C., Zhang, C., Wang, S.,
Wang, L., Gao, W., Liu, Y.
and Zhao, C.
2019
Increased drought and
atmospheric CO2 positively
impact intrinsic water use
efficiency but do not promote
tree growth in semi-arid areas
of northwestern China.
Trees 33: 669-679.
SUMMARY:
Lu et al. report that
intrinsic water use
efficiency (iWUE),
increased by +32%
since 1955.
They estimate 98%
of the change is due to the
+23% rise in atmospheric CO2,
which had a large reducing
effect on stomatal conductance.
It's very likely that a
rising CO2 level will
lead to growth-enhancing
and water-saving effects.
that offset
the negative impacts
of drought on the growth
of these trees
( and a lot sooner
if climate conditions causing
the drought are eased ).
DETAILS:
Lu et al. (2019) examined
sixty years of climate
and tree-ring data
to investigate the impact
of rising atmospheric CO2
and drought on the growth
and water use efficiency
of trees growing in the
Xinglong Mountain National
Nature Reserve, located at
the intersection of the
Qinghai-Tibet, Loess and
Neimenggu-Xinjiang plateaus.
This semi-arid site
has experienced
rising temperatures and
declining precipitation
over six decades,
leading to a l
ong-term drought
over the period 1955-2014,
evidenced by the downward
linear trend of the Palmer
Drought Severity Index.
The sustained drought
in this already semi-arid
region has had
a negative effect
on tree basal area
increment (BAI).
The negative effect
reversed direction
since 1980, inducing
a positive trend
in BAI since that time
(green shading),
returning to values
witnessed at the
beginning of the record.
