Summary
Observational
evidence
indicates
that
tree
leaf
area
may
acclimate
in
response
to
changes
water
availability
alleviate
hydraulic
stress.
However,
the
underlying
mechanisms
driving
and
consequences
of
different
allocation
strategies
remain
unknown.
Here,
we
use
a
trait‐based
hydraulically
enabled
model
with
two
endmember
strategies,
aimed
at
either
maximizing
carbon
gain
or
moderating
We
examined
impacts
these
on
future
plant
stress
productivity.
Allocating
maximize
increased
productivity
high
CO
2
,
but
systematically
Following
an
strategy
avoid
missed
out
26%
potential
net
primary
some
geographies.
Both
resulted
decreases
under
climate
scenarios,
contrary
Earth
system
(ESM)
predictions.
Leaf
acclimation
(and
potentially
risk
accelerated
mortality)
was
possible,
led
reduced
gain.
Accounting
for
effects
canopy
ESMs
could
limit
reverse
current
projections
increases
area,
cycles,
surface
energy
budgets.
Journal of Ecology,
Год журнала:
2023,
Номер
111(12), С. 2676 - 2693
Опубликована: Окт. 18, 2023
Abstract
Plant
biomass
production
(BP),
nitrogen
uptake
(
N
up
)
and
their
ratio,
use
efficiency
(NUE)
must
be
quantified
to
understand
how
(N)
cycling
constrains
terrestrial
carbon
(C)
uptake.
But
the
controls
of
key
plant
processes
determining
NUE,
including
BP,
C
allocation,
tissue
C:N
ratios
resorption
(NRE),
remain
poorly
known.
We
compiled
measurements
from
804
forest
grassland
sites
derived
regression
models
for
each
these
with
growth
temperature,
vapour
pressure
deficit,
stand
age,
soil
fAPAR
(remotely
sensed
fraction
photosynthetically
active
radiation
absorbed
by
green
vegetation)
growing‐season
average
daily
incident
photosynthetic
photon
flux
density
(gPPFD;
effectively
seasonal
concentration
light
availability,
which
increases
polewards)
as
predictors.
An
empirical
model
leaf
was
based
on
optimal
capacity
(a
function
gPPFD
climate)
observed
mass
per
area.
The
were
used
produce
global
maps
NUE.
Global
BP
estimated
72
Pg
C/year;
950
Tg
N/year;
NUE
76
g
C/g
N.
Forest
found
increase
temperature
decrease
ratio
gPPFD.
is
controlled
primarily
climate
through
its
effect
allocation—especially
leaves,
being
richer
in
than
other
tissues.
greater
colder
climates,
where
less
readily
available,
because
below‐ground
allocation
increased.
also
drier
climates
reduced.
NRE
enhanced
(further
promoting
NUE)
both
cold
dry
climates.
Synthesis
.
These
findings
can
provide
observationally
benchmarks
representations
C–N
cycle
coupling.
State‐of‐the‐art
vegetation
TRENDY
ensemble
showed
variable
performance
against
benchmarks,
coupled
produced
relatively
poor
simulations
Geophysical Research Letters,
Год журнала:
2023,
Номер
50(21)
Опубликована: Ноя. 6, 2023
Abstract
Increased
plant
growth
under
elevated
carbon
dioxide
(CO
2
)
slows
the
pace
of
climate
warming
and
underlies
projections
terrestrial
(C)
dynamics.
However,
this
important
ecosystem
service
may
be
diminished
by
concurrent
changes
to
vegetation
carbon‐to‐nitrogen
(C:N)
ratios.
Despite
clear
observational
evidence
increasing
foliar
C:N
CO
,
our
understanding
potential
ecological
consequences
stoichiometric
flexibility
is
incomplete.
Here,
we
illustrate
that
when
incorporated
‐driven
increases
in
stoichiometry
into
Community
Land
Model
projected
land
C
sink
decreased
two‐fold
end
century
compared
simulations
with
fixed
chemistry.
Further,
profoundly
altered
Earth's
hydrologic
cycle,
reducing
evapotranspiration
runoff,
reduced
belowground
N
cycling
rates.
These
findings
underscore
urgency
further
research
examine
both
direct
indirect
effects
changing
on
soil
productivity.
Research Square (Research Square),
Год журнала:
2024,
Номер
unknown
Опубликована: Янв. 5, 2024
Abstract
Terrestrial
ecosystems
play
a
pivotal
role
in
mitigating
climate
change
through
photosynthesis
and
transpiration
regulated
by
plant
stomata.
biosphere
models
(TBMs)
commonly
couple
biochemical
model,
i.e.,
the
Farquhar
semi-empirical
stomatal
conductance
Ball-Berry
to
estimate
gross
primary
productivity
(GPP)
evapotranspiration
(ET).
However,
key
ecosystem
parameters
(i.e.,
maximum
carboxylation
rate
Vcmax
slope
m)
are
prescribed
as
constant
TBMs,
hindering
accurate
quantification
of
global
GPP
ET.
m
depicts
‘compromise
between
costs
benefits
relative
photosynthetic
activity
leaf’,
namely
sensitivity
photosynthesis.
although
recent
work
has
retrieved
continuous
seasonal
V_cmax
over
globe,
there
is
lack
an
effective
method
derive
spatially
temporally
explicit
TBMs.
In
this
study,
we
estimated
monthly
Bayesian
parameter
optimization
approach
at
136
eddy
covariance
flux
sites
(809
site
years)
upscaled
site-level
gridded
during
2001-2020
via
machine
learning
model.
We
found
significant
declining
trend
(R2
=
0.72,
P
<
0.001)
2001-2020.
largest
decline
grassland
(0.04
per
year),
moderate
declines
deciduous
broadleaf
forests,
mixed
cropland
(0.02
smallest
evergreen
needleleaf
forests
savannas
(0.01
year).
air
temperature
plays
predominant
driving
m.
This
study
generates
analyzes
timeseries
‘handshaking’
measured
fluxes,
terrestrial
models,
remote
sensing.
Our
results
highlight
changing
relationship
under
identify
importance
incorporating
dynamic
future
ET
simulations
with
models.
Summary
Observational
evidence
indicates
that
tree
leaf
area
may
acclimate
in
response
to
changes
water
availability
alleviate
hydraulic
stress.
However,
the
underlying
mechanisms
driving
and
consequences
of
different
allocation
strategies
remain
unknown.
Here,
we
use
a
trait‐based
hydraulically
enabled
model
with
two
endmember
strategies,
aimed
at
either
maximizing
carbon
gain
or
moderating
We
examined
impacts
these
on
future
plant
stress
productivity.
Allocating
maximize
increased
productivity
high
CO
2
,
but
systematically
Following
an
strategy
avoid
missed
out
26%
potential
net
primary
some
geographies.
Both
resulted
decreases
under
climate
scenarios,
contrary
Earth
system
(ESM)
predictions.
Leaf
acclimation
(and
potentially
risk
accelerated
mortality)
was
possible,
led
reduced
gain.
Accounting
for
effects
canopy
ESMs
could
limit
reverse
current
projections
increases
area,
cycles,
surface
energy
budgets.
