Li, L.,
Manning, W.
and Wang, X.
2019.
Elevated CO2 increases
root mass and leaf nitrogen
resorption in red maple
(Acer rubrum L.).
Forests 10: 420; doi:10.3390/f10050420.
NOTE:
An examination of the
leaf nitrogen (N) content,
N resorption efficiency
and biomass allocation
responses of this
deciduous tree species
that is widespread
across eastern and
central North America.
Nitrogen resorption efficiency
(NRE),
which is defined
as the process
by which N is mobilized
from senescent leaves
and transported to other
plant parts.
Improved NRE,
from elevated CO2,
would counteract
the leaf N decline
often observed in tree
leaves at high CO2 levels.
SUMMARY:
Total dry mass produced
at the end of the growing
season at the three
different CO2 treatments,
which shows that the trees
in the 800 ppm treatment
experienced a +19.2%
growth enhancement
compared to the ambient
(400 ppm) CO2 treatment.
No biomass difference
was found between trees
growing in the ambient
and 600 ppm CO2 treatments.
The N content
of senescent leaves
declined by
27.5% and 28.1%
(relative to ambient CO2)
in the 600
and 800 ppm
CO2 treatments,
respectively.
But elevated CO2
also enhanced NRE,
by +46.2% and +50.3%
at 600 and 800 ppm CO2,
respectively.
"Higher NRE
of senescent leaves
makes [it] possible [for]
more nitrogen transfer
to other plant organs
for early growth
[the] next year."
N resorption efficiency (NRE),
is enhanced under elevated CO2 ,
counteracting leaf N decline
at high levels of CO2.
Thanks to elevated CO2,
NRE is becoming
"an increasingly important
N source" for red maple,
and likely other trees
and plants.
DETAILS:
Working with nine continuously
stirred tank reactor chambers
located inside a glass greenhouse
at the University of Massachusetts,
Li et al. (2019) recently exposed
two-year-old red maple seedlings
(Acer rubrum) to three different
concentrations of atmospheric CO2
over the course of
one full growing season.
