Jpn. J. Limnol., 52, 4, 263-281, 1991
Review
Gas
Exchange
in Ecosystems:
Framework
Eitaro
and
WADA, John A. LEE,
William
Case
Studies
Makoto
KIMURA, Isao
S. REEBURGH, Jose G. TUNDISI, Tadashi
Takahito
YOSHIOKA,and Margret
KOIKE,
YOSHINARI,
M. I. VAN VUUREN
Abstract
This report
is an extended
summary
of the symposium
on "Carbon
and Nitrogen
Cycles in the Biosphere and Geosphere" in INTECOL '90 held at Yokohama on 28
August 1990. The general ideas and aspects of nitrogen and carbon dynamics in
ecosystems
are described
along
with atmospheric
nitrogen
biogenic gases such as carbon dioxide, methane, molecular
Increases of the radiatively active gas concentrations
atmosphere
are described
ments and food demand.
supply,
and behavior
of
nitrogen and nitrous oxide.
(CO2, CH4, and N2,O) in the
in connection
with human
impacts
such as energy
The increase
in atmosheric
carbon
dioxide has been caused
by fossil fuel combustion, that is, a man-made
C-O-Fe-S cycle.
Increase in crop production
require-
short circuit between atmosphere and
dominates the fluxes of mineralization
processes of organic matter both in aerobic and anaerobic conditions, resulting
in the
enhancement
of methane and nitrous oxide production in the whole biosphere.
Several current efforts to investigate atmosphere-biosphere
interactions are schematically summarized for site specific phenomenon such as plant-soil associations and
for some representative
ecosystems
(heathland,
rice rhizosphere,
tundra and taiga,
lake, tropical
reservoir,
Key words: Oxygen
1.
coastal
and estuarine
cycle, human
impact,
system, and global
atmospheric
N2O cycle).
deposition,
biogenic
gases
biochemical pathways that transport the bioelement directly between the atmosphere
and the
Introduction
One among the principal prerequisites
for the
evolution and survival of terrestrial
life is the
biosphere.
cycling of bioelements
3.5 billion
under moderate
climate.
appearance
The
primary
highlight
of photosynthetic
years
ago.
was
the
organisms
some
Two biochemical
path-
Atmospheric
and water circulations
play a
major part in the operation of biogeochemical
ways, fixation of carbon
tion of molecular oxygen,
cycling
sions for the cycling of matter and the evolution
on the Earth's
ment such as hydrogen,
surface.
carbon,
Each
bioele-
nitrogen,
and
of the atmoshere
dioxide and producprovided new dimen-
as known
in the present
bio-
oxygen completes its biogeochemical
cycle as
being major or minor components in the atmo-
sphere.
initiated
sphere
MARSHALL,1964) and the framework
of biogeo-
chemical
and sulfur
genesis
and
the circulating
of life, living
* Symposium
organizer
water.
organisms
After
evolved
the
new
The increase in atmospheric
oxygen
some 2 billion years ago (BERKNERand
cycling of carbon,
nitrogen,
264WADA
, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSIIINARI, YOSHIOKA and
was completed
by the evolution
oxidation-reduction
ments.
Evolution
of microbial
pathways
of these eleof the biosphere has then
been closely associated
with these cycles.
The
C-O-Fe-S
the partial
cooperating
geological cycle keeps
pressure of atmospheric
oxygen at
its present
level (GARRELSet al., 1976).
There is a considerable interest in the level of
the partial
pressure
of atmospheric
carbon
dioxide
an
during
the Precambrian
apparent
period
contradiction
due to
between
the
certainly
introduces
VAN VUUREN
the increasing
of oxidation-reduction
fields, wetlands,
occurrence
boundaries
and aquatic
in cultivated
ecosystems.
The
anthropogenic
impacts are manifest
as two
manmade short circuits between atmospheric
carbon
dioxide
and the geological
carbon
cycle
(fossil fuel combustion)
and between atmospheric dinitrogen and the short term biogeochemical
tion).
nitrogen
In this report
cycling
(artificial
N2 fixa-
the global
cycling
of bioele-
continued existence of life and the early, faint
Sun that is predicted by the present models of
ments is summarized
biosphere interactions
to address atmospherewith emphasis on current
solar
global environmental
deposition, ecosystem
problems.
processes,
evolution
(KUHN and
KASTING, 1983;
WALKER,1983; NEWMANand ROOD,1977).
In this
context, carbon isotopic studies of Precambrian
rocks appear to provide a piece of biogeochemical
evidence;
the
atmospheric
carbon
dioxide content was two orders of magnitude
higher during most of the Precambrian
than the
consumption
presented
involving
lacustrine
even
today.
At present
the
Earth's
surface
production
of
gases
are
for several representative
ecosystems
forests, tundra and taiga systems,
environments,
coastal
and estuary
areas, and open oceans.
present level (MIZUTANIand WADA, 1985). Our
atmosphere is the product of the past 3.8 billion
years of life and the biosphere has lived in a
global green house during the continuous existence of life. The Earth's greenhouse
effect
has changed over geologic time and is changing
and
Atmospheric
and biogenic
2.
Biogeochemical
From the biogeochemical
cycles
standpoint,
bioele-
ments are characterized
as having stable forms
of molecules in three phases such as gas, liquid
and solid.
late each
This fact makes it possible to circuelement through biosphere, hydros-
temperature
is raised about 35'C above what it
would be if no radiatively
active gases were
phere, and atmosphere.
evolution of biochemical
present (HILEMAN,1989).
Since the pioneering work
gaseous substrates
and products plays a decisive role in biogeochemical
cycling in the pres-
surements
of atmospheric
centration
at Mauna
of monthly
carbon
dioxide
Loa by Charles
meacon-
KEELING
In this context,
the
reactions concerning
ent biosphere.
These biochemical
processes
are CO, and N2 fixation, and N2, N2O, CH, and
(KEELING et al., 1976), considerable
attention
has been paid to the increases in atmospheric
production.
In the
sphere, practical
operation
deposition
ing from
accepted to have evolved some 2 billion years
ago when oxygen partial pressure was raised up
which
and radiatively active gases originatexpanding
anthropogenic
impacts,
principally
result
from
the
increasing
pressure of human population and can be characterized in terms of energy requirements
and
food demand.
For example, carbon dioxide
and NOX generally
combustion,
while
originate
methane
from fossil fuel
and nitrous
oxdie
are byproducts or end products in the process of
microbial
decomposition
of organic
matter.
Global dynamics
are thus closely
of the latter two compounds
correlated
with agricultural
crop production
of which
expanding
increase
H,S
to 10-2 of PAL
The
(present
accumulation
history
of the
bio-
of these processes
atmospheric
of atmospheric
is
level).
oxgen
is
generally accepted by the occurrence of continental "red beds" (JUNGE et al., 1975). After
the increase in PD, in the atmosphere,
operations of all biological
mary governed
processes
have been pri-
by the existence
of molecular
oxygen in the atmosphere.
At present molecular oxygen is the most efficient electron acceptor in our respiratory
and also determines
energy
yielding
the stability
system
of chemical
Gas Exchange
forms
of
tion
other
reactions.
terminal
In
on
cycles
in
the
present
the
bioelements
can
the
following
Turn
of
oxygen
time
places
a
biogeochemical
(Fig.
oxygen
in
be
1).
the
other
expressed
atmospheric
time
atmosphere
as
oxygen
as
a
by
amount
annual
rate
Where
the
in
molecular
of
oxygen
in
the
02
in
the
one
equivalents
molar
02=1-0
nitrogen=4/3
can
molar
molar
be
car-
Fee-=1/2
in
kinds
terms
of
of
decomposition
biosphere.
production
Fig. 1.
turn
into
Organic
such
organic
over
matter
time
gaseous
Oxygen
grass,
via
crop,
and
SVENSSON (1976),
classi-
in
annual
to
leaf,
The values
can
the
be
on biogenic
used for annual
Nitrification
primary
formed
tion
of
the
accumulation
molecular
gas productions.
are all equivalent
and GARRELS et al.,
(1990) are also included.
the
(1976).
rate
production
to molar O2
Data
and
of
this
105
from
was estimated
was nitrate.
BOLIN
time
of
al.,
been
1979)
If
103
this
cycle,
in
The
rocks
which
be
net
organics,
values
of fluxes are
SODERLUNDand
total
see text.
has
produc-
estimated
sedimentary
by assuming
we
oxygen
OHTAKE (1978), and BOUWMAN
Details,
for
then
cycle.
sedimentary
after
we
years
accumulated
C-O-Fe-S
in
can
of
(38•~1018/320
pool
Revised
et
Molecular
oxygen
in
pool
1977),
years
has
Numerical
indicated
inventory.
group.
of
organic
large
RAYNER,
geological
by
not
C,
over
atmosphere
organic
accounts
years.
second
carbon
turn
for
largest
molecular
process
are
the
(JENKINSON
through
been
primary
cycle with emphasis
1012 mole•yr-1.
nitrogen
be
respect
products
matter
as
can
with
the
over
decomposed
of
dissolved
atom
average
estimate Ą(O2)
this
peat
organic
can
in
and
(320•~1015g
pool
is
matter,
constitute
this
turn
almost
amounts
organic
global
an
short
produced
of
oceans,
•~ 1015•~10-3)
sulfur.
Several
in
1, these
a
ecosystems
(38•~1018/17,000•~1012)
soil
adopt
molar
matter
2•~103
the
many
equivalent
ca.
in
of
In
The Ą(O2)
Fig.
atmosphere/
year.
organic
Although
a process],
following
molar
consuming
organics
of
practice;
bon=2/5
the
by
matter
of
representative
one
all
for
turn-
defined
as
of
oxygen.
cycles
(Ą, year)
=[total
molar
regarded
equation:
over
used
oxidation-reduc-
biosphere
of
time
sense,
cooperating
cooperation
over
in
this
the
The
of
fied
bioelements
265
in Ecosystems
inorganic
from
as
266
one
WADA, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSHINARI, YOSIIIOKA and
molar
buried
molecular
carbon
oxygen.
partitioning
of
between
free
reservoir
The Ą(O2)
by
bond
pool
as
cycle
a
only
the
estimated
from
primary
We
tion
of
the
total
N•yr-1
equals
to
nitrate
produced
porated
its
here
is
(WADA
to
and
HATTORI,
this
then
018/5•~1014)
ca.
r(O2)
becomes
(Fig.
ca.
105
One
way
to
outline
past
is
to
compare
of
factors
with
primary
in
atmospheric
gases.
Since
impacts
the
changes
N2
plus
(38
were
The
ppm)
is
every
year
lower
resulting
CH,
plus
products,
N2O
and
impacts
gases
(CO2,
CH4,
after
increasing
the
et
1976,
percentage
fule
War
II.
CO,
(340
than
1 ppm
1979),
annual
(Fig.
fossil
the
pro-
the
more
al.,
for
N2O)
World
of
population
one
part
billion
nearly
the
equal
which
is
growth
3)
rate
(OFITAKE,
burning
1978).
annually
remains
The
lower
the
atmosphere
adds
the
in
the
(PEARMAN
1990).
Each
year,
Main
of
(CICERONE
(Ą(O2)).
time
of
of
tion.
these
organic
and
are
closely
Consequently,
in
level
the
million
the
more
are
the
to
increase
lands
and
the
burning)
The
the
than
wet
(biomass
1988).
,
tons
atmosphere
of
fermentation
related
of
BOUWMAN
50
matter
,
changing
methane
OREMLAND,
as
forest
1988;
increase
intestinal
in
such
the
is
additional
of
CO2
gases,
remains
CO2
ocean.
FRASER,
annual
of
harvested
the
car-
1989).
growth
of
house
an
sources
fields,
pyrolysis
of
and
COQ
of
population
sinks
atmosphere
methane
an
rate
of
green
fastest
released
the
action
biogenic
tons
increasing
of
vege-
the
(HILEMAN,
regrowth
buffering
from
billion
atmosphere
than
atmosphere.
Of
2.5
variety
biota,
paddy
residence
the
a
the
generated
about
in
from
1%.
is
to
destruction.
percentage
the
CO,
amount
annually,
bon
of
soil
representing
on
tons
and
released
biogenic
of
A
six
tation
increases
of
in
the
change
of
oxygen
(FFC)•¨CO2
plus
(KEELING
present,
methane
atmospheric
require(FD),
combustion
burning
currently
human
Of
illustration
following
demand
concentration
than
and
Schematic
Food
accelerated
present
terrestrial
2.
the
(PG)•¨Energy
plus
active
results
Fig.
anthropogenic
by
CH4
duction
the
during
temporal
concentrations
the
expanding
The
impacts
human
the
biosphere.
anthropogenic
some
recent
vari-
general
production•¨Decomposable
radiatively
of
anthropogenic
present
matter•¨CO2
plus
2).
Expanding
expect
all
ER+FD•¨Deforestation+Cattle•¨CO2
At
3.
the
fuel
organic
The
incor-
years
change
Aerosol,
plus
of
by
not
qualitative
growth
FD•¨Crop
iv)
which
be
the
among
represented
(ER)
plus
iii)
part
could
be
with
could
variation
along
can
ER•¨Fossil
be
2•~1014g
1991),
process
ii)
in
annual
A
denitrification.
nitrification
be
in
Population
utiliza-
The
the
we
expect
occur
ment
(OHTAKE,
mole O2•yr-1.
in
into
uptake.
i)
global
nitrate
of
cycles,
processes.
can
ratio
60%
estimated
500•~1012
events
impacts
denitrifica-
during
C/N
ca.
nitrogen
rate
atom
uptake
and
assume
nitrification
•~1
nitrogen
main
atmo-
rate
the
could
years
cycle
and
but
interlinked
of
figures
ables
nitrogen
oxygen
nitrification
production
1978).
the
always
part
similar
the
the
are
other
to
nitrogen,
The
in
trends
stability
in
nitrification
maximum
0.05:
system
1990).
107
the
exists
with
bound
is
ca.
of
component.
of
The
is
molecular
cooperates
the
WADA,
process
nitrogen
major
processes
tion.
of
of
of
the
02
present
1975;
Because
triple
sphere
and
at
al.,
this
mole
that
produced
SO42-)
et
(38•~1018/2.5•~1012).
the
one
accepted
02)
plus
value
largest
now
(atmospheric
(SCHIDLOWSKI
of
is
photosynthetically
(Fe2O3
0.95
produces
It
VAN VUUREN
last
crop
in
three
produc-
the
meth-
,
Gas
Fig. 3.
Temporal
variations
production,
ane concentration
radiatively
production.
with the popula-
267
in Ecosystems
active
gases,
exhibits
a
0.3%
annual
which is not as fast as methane,
from 280 ppb at the turn of this century
methane
modes
rising
The detailed
microbial,
ecological
to 303
chemical
studies
exchange
time is rather long (ca. 100 years)
with methane
(ca. 10 years).
sources
of the increased
might
matter
tons of N2O into the atmoturn
oxide
over
as compared
The major
nitrous oxide are fertil-
human
of ecosystems
to elucidate
activity
on
are shematically
point, we would like to emphasize
sion to approach
this problems.
a new dimenStable iso-
sphere
biological
hydroxyl
radicals,
gas
illus-
trated in Figure 4 with emphasis on fossil fuel
combustion
and crop production.
At this
topes of light elements such as carbon
nitrogen undergo fractionation
in chemical
with
de-
and biogeo-
ized soils, and biomass and fossil fuel burning.
Most of the methane is removed from the tropoby oxidation
from
during
in ecosystems.
will be required
of
result
of production
of organic
tion of 5 million
Its tropospheric
rice crop
composition
this point.
Perturbations
each year.
population,
and nitrous
ppb at present (RASMUSSENand KHALIL, 1986;
BOUWMAN,1990). This results from the injecsphere
human
CFCS: chlorofluorocarbons.
the different
tion growth.
Nitrous
oxide
increase
of atmospheric
and fertilizer
is correlated
Exchange
reactions.
Biogenic
and
and
materials
in
while the only known atmospheric sink for NZO
is its breakdown to NO in the stratosphere
by
global cycles of the light elements have their
own isotopic composition,
so-called "dynamic
ultraviolet
light
stable
Differences
in the annual increase
(YOSHIDAand MATSUO, 1983).
rate between
isotope
a fluctuation
(SI) finger print".
of a molecule's
In principle,
isotope
ratios
268
WADA, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSIIINARI, YOSHIOKA and
Fig. 4.
Schematic
illustration
of the perturbation
of carbon
and nitrogen
VAN VUUREN
cyclings
by the human
impact.
provides information
about its origin, pathways, and the reaction mechanisms concerning
its formation.
On a macroscopic
level , SI
for nitrate
chemical
markedly
Northern
Hemisphere.
in many
deposition
show
can provide
two and four fold depending
solve
biogeochemical
phenomena
involving
transport
of organic
A., unpublished).
In many near pristine
turbation
in an ecosystem.
to
matter
and per-
For example,
the
regions
For example
of an ecosystem
a key
structure
increased
of the
estimates
increases
between
on location
environments
(LEE, J .
nitrogen
supply can be shown to be a major determinant
CO2 increase in the atmosphere
and its carbon
isotope ratio follow a single mixing (KEELINGet
of plant
growth,
content
of plant
al., 1979) and every one ppm of the CO, added
sition
and mineralization
processes.
increases in combined nitrogen deposition
to the atmosphere introduces the ratio changes
of about -0.02 %o (MOOK et al ., 1983). Several
examples will be shown in the following case
studies.
4.
combined
atmosphere
widespread
Evidence
Atmospheric
ecosystem
During
the
nitrogen
nitrogen
from
emissions.
Century
deposition
the atmosphere
in the nitrogen
may
be having
decompoThus
from
marked
and
effects on ecological
processes.
is now accumulating
to support
the
view that terrestrial
ecosystems are being perturbed markedly
by anthropogenic
nitrogen
supply and
process
the Twentieth
and increases
litter can accelerate
of
has
These
and heathland
deposition
include
ecosystems
represents
ombrotrophic
where
an important
mires
atmospheric
source
of
Gas Exchange
bioelement.
In the most polluted
ecosystems
can
be
shown
regions these
to
be
269
in Ecosystems
(Beizexose,
atmospheric
adversely
1990).
Nowadays,
the increased
deposition of nitrogen accelerates
affected by atmospheric
nitrogen
deposition.
However as nitrogen accumulates
in plants and
the succession
soil
as Molinia
organic
matter
the
change in ecosystems
to an alteration
potential
for
latent
which are less susceptible
(Plate
there
has
grasses such
2).
in nitrogen
nant, the nitrogen
potential
the
importance.
availability
created
species
cycle is strongly
itself.
The
affected
above-
and
by
below-
ground biomass production
and the amount of
litter is greater in Molinia as compared to Erica
5.
5-1.
cacrulea
As a result,
of perennial
suitable conditions for the spread of Molinia.
However, once this species has become domi-
or in less polluted regions becomes more pronounced.
This change is difficult to assess, but
and increasing
increase
The increase
in the aerial supply of elements
may of considerable
process.
been a strong
Case studies
The impact
upon
or Calluna
of dominant
nitrogen
cycles
plant
in
species
heathland
ecosystems
(M. I. MARGRET)
Heathlands
in the Netherlands
have
dominated
heathlands
(Aioers and
BERENOSE,1989; Ar;Rrrs et al., 1989).
Molinia
litter
concentration,
immobilisation
devel-
has
a relatively
Although
low
nitrogen
which leads to a net nitrogen
in the first stage of decomposi-
oped on sandy
soils and used to be dominated
tion,
by ericaceous
shrubs
Erica
(Plate
produced by Erica or Calluna due to its relatively low lignin content.
As a consequence,
a
tetralix
succession,
nitrogen
like Calluna
1).
vulgaris
or
At the beginning
of
supply through
tion is very low in these ecosystems.
mineraliza-
it decomposes
greater
through
However,
much
ing in the soil organic
to
influence
higher
nitrogen
mineralization
rates
Plate
1.
Erica
the dominant
lctralix.
than
litter
amount of nitrogen
will be supplied
mineralization,
instead of accumulat-
the amount of soil organic matter increases by
the input of plant litter, which gradually leads
that
faster
layer.
plant
It was concluded
species
on the rate of nitrogen
have
a clear
cycling in these
270
WAnA.
LjAc, KIMURA, KOIKE, REEBURGH,TUNDISI,
Plate
2.
Molinia
ecosystems.
5-2. Production of biogenic gases in rice
rhizospheres and their transfer to the
atmosphere (M. KIMURA)
The fact that paddy rice grows in the submerged (reduced) environment characterizes the
kinds and amounts of biogenic gases produced
in the rhizosphere and their transfer to the
atmosphere.
Contrary to the general understanding, the
rice rhizosphere is not always oxidative. It
becomes reduced from the maximum tillering
(MT-) stage in growth, and the biogenic gases
are produced sequentially as growth proceeds;
the production of CO,, and N,O and N, by
denitrification occur in the early growth stage
and the denitrification terminates before the
MT-stage.
Hydrogen production is observed
around the MT-stage.
Methane production
begins after that.
The root system consists of roots of different
ages, and old roots produce the reducing environment where H, and CH, production and
SO,'- reduction occur. Hydrogen is produced
in/on the roots, and the main sites of CH4
YOSHINARI, YOSHIOKA and VAN
VIIREN
caerulea.
production
rhizosphere
and SO42- reduction
are
soil. Hydrogen
produced
roots is selectively
utilized
in the
in/on
for sulfate reduction
in the rhizosphere.
Thus, the production
different
of each biogenic
to one another
is controlled
gas is
in time and space, and
by the growth
stage of paddy rice
(CICERONEand SHETTER, 1981; CICERONEet al.,
1983; DE BONTet al., 1978; HOLZAPFEL-PSCHORN
et
al., 1986; HOLZAPFUL-PSCHORN
and SEILER, 1986;
MINAMIand YAGI, 1988; SEILERet al., 1984).
The transfer of CO, and CII, produced in the
rhizosphere is different due to the difference of
solubility to water (Fig. 5).
CO2 is absorbed by rice roots, and transferred
to
the
shoot
and
then
to the
atmosphere
(HR.ucHI et al., 1984; WAUA et al., 1983;
YOKOYAMA
and WADA, 1983). Some portion of
absorbed CO, is photosynthesized
by the shoots.
The mechanisms
of transfer
of CO, through
plants is still controversial.
consider it to be associated
transpiration,
and otheres
Some scientists
with the flow of
consider
it to occur
by diffusion in gaseous state through intercellular spaces of the aerenchyma
in the root
Gas Exchange
Fig. 5.
Schematic
t ransfer
cortex.
CO2 remaining
subsoil
illustration
showing
production
271
in Ecosystems
of biogenic
gases in rice rhizoshere
be present
in bubbles,
and their
to the atmosphere.
in the soil is carried
to the
in the form of HCO3- with the move-
atmosphere
evidence
partly
that
by
and
it is carried
ebullition,
transfers
occur
but
mainly
to the
there
is
through
ment of leaching
water.
Rice plants
are
known to influence this CO2 leaching (TSUCHIYA
root-shootpathway(INUBUSHI
et al.,11989).
et al., 1984).
paddies
Due to the low solubility of methane
it is not leached downward.
in water,
It is considered
to
The
emission
were
rates
of methane
not altered
by cutting
from
rice
the rice
plants above the water level. So the transfer is
considered to be due to the gaseous diffusion
272
WADA, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSHINARI, YOSHIOKA and
not due to the transpiration.
The main route
of methane emission is considered to be through
old roots to the shoots. Some portion of methane may be oxidized on its way to the atmosphere.
5-3. The role of tundra and taiga systems
in the global methane budget (W. S.
REEBURGH
and S. C. WHALEN)
Tundra and boreal forest soils contain some
30% of the terrestrial soil carbon reservoir
(Pose, et al., 1982). A large fraction of this soil
carbon is immobilized in permafrost and peat.
This soil carbon reservoir could be susceptible
to biogeochemical conversion to CO, and CH,
under warmer, wetter climates. Both of these
gases are radiatively active, and could be
responsible for a positive climate feedback .
We evaluated the importance of tundra and
taiga systems in the present global CH, budget
and studied processes important in modulating
emissions under present and modified climates
with weekly measurements of CH, flux at a set
of permanent sites (WHALENand REEBURGH,
1988, 1990a). Our CH, flux time series at tundra sites in the University of Alaska Arboretum
covers over 3.5 years and indicates that water
table level, transport by vascular plants and
microbial oxidation at the water table are
important in modulating tundra CH, emissions.
Emissions of CH, essentially cease during frozen periods. Our study at permanent taiga
sites involves one set of flux measurement in
October, 1989, and weekly measurement from
May to October 1990. All taiga sites except
those adjacent a river consumed atmospheric
methane, indicating that these soils are sink for
atomspheric CH4.
Integrated annual emissions from the seasonal time series measurements and results
from a detailed survey along the Trans Alaska
Pipeline Haul Road lead to independent estimates of the global tundra CH, flux of 19-33
and 38 Tg•yr-1, respectively (WHALENand
REEBURGH,
1990b; REEBURGH
and WHALEN
, 1990).
The road transect estimate for the global taiga
CH, contribution is 15 Tg•yr -1.
Microbial oxidation of methane is an important modulator of tundra fluxes (REEBURGH
and
WHALEN,
The
1990;
WHALEN
process
the
is
water
at
in
rates
rapidly
tion
is
moist
the
suggests
control
serve
as
a
the
for
occurs
Methane
oxida-
more
important
Preliminary
process
methane
sink
but
equilibrate
conditions.
that
tundra
adjacent
which
become
drier
1990b).
region
soils,
soils,
to
warmer,
work
the
atmosphere.
expected
under
REEBURGH,
to
waterlogged
in
with
and
restricted
table
high
VAN VUUREN
could
not
emissions,
only
but
atmospheric
also
methane
(Fig.
6).
5-4.
Metabolism
of
lacustrine
Aquatic
ecosystems
ponents
ratios,
tion
on
the
may
tion
of
the
content
ments
biogenic
will
with
the
gas
the
biological
Stable
shallow
km2;
max.
spheric
CO2,
pH
values
and
the
at
al.,
by
bloom
S13C,,,c
value
chemical
kinetic
be
CO2
pleted
CO2
processes
seem
assimilation
contribute
during
10
water
photo-
conditions
affected
CO2
invasion
of
the
from
negative
with
supply
,
by
large
the
of
equi13C
de-
decomposition
also
the
in
phytoplankton,
and
fractionation
about
intense
these
the
respiration
lakes,
rise
the
largely
The
season
CO2
compared
to
the
of
shows
exchange.
from
Since
often
of
which
fractionation,
librium
summer
forming
may
atmo-
eutrophic
Under
enhancement
atmosphere,
the
of
those
with
In
because
13.3
than
equilibrium
in
ina eutro-
area,
lower
waters
low
Microcystis.
with
dissolved
Suwa,
(surface
pressure
as
the
the
vary
of
were
1990).
partial
synthesis
of
because
Lake
Japan
surface
quite
biological
largely
in
m),
waters
of
becomes
CD,G.
in
6.8
et
the
processes
ratios
particularly
(TAKAHASHI
environinterations
depth.
lake
for
composi-
by
by
lakes
(ƒÂ13CDIC)
depth,
observed
only
also
isotope
carbon
phic
the
water
and
step.
isotope
interface,
in
carbon
organic
such
but
iso-
fractiona-
lacustrine
consumption
air-water
with
with
stable
important
the
in
not
activities
and
activities
aqueous
most
and
governed
and
below
time
the
atmosphere,
production
com-
isotope
gases
be
gaseous
between
be
in
YOSHIOKA)
their
equilibrium
exchange
phases
However,
biological
Concerning
gas
gaseous
CO2
from
atmosphere.
tope
components
(T.
exchange
resulting
the
gaseous
ecosystems
to
the
low
813
photosynthetic
summer
season
in
Gas Exchange
273
in Ecosystems
Waterlogged-Saturated
Fig. 6a.
Schematic
solis.
diagram
Oxidation
boundary.
Methane
showing
occurs
Transport
fluxes
controls
on methane
in the vicinity
of methane
to the atmosphere
Fig. 6b.
Schematic
diagram
occurs throughout
lar diffusion.
fast
relative
atmospheric
showing
are positive
controls
to biological
methane
soil interval
consumption
in waterlogged
table,
by aqueous
which
phase
and saturated
is the oxic: anoxic
molecular
diffusion.
(REEBURGH and WHALEN, 1990).
Soils
on methane
the moist soil interval.
The moist
oxidation
of the water
is controlled
Moist
Soils
oxidation
Transport
equilibrates
rates.
in moist
is controlled
soils.
with the atmosphere
Moist
(REEBURGH and WHALEN, 1990).
soils
are
Oxidation
by gas phase
capable
molecu-
at rates that
are
of consuming
274WADA
Lake
in
, LEE, KruuRA,
Suwa
the
was
These
zone
duration
of
Suwa,
the
are
ecosystem
tion
process
spp.
Since
shows
by
flow
can
be
In
of
to
be
a
et
al.,
N20
1988a,
the ƒÂ15N
than
that
the
remaining
very
of
NO3-
the
N03
in
value
YOSHIOKA
et
suggested
that
emit
the
in
whole
al.,
to
N2O
seemed
oxic
1988).
the
al.,
These
period
Fig. 7.
of
and
and
Lake
Schematic
of producing
opportunities
Newly constructed
had
of in-
aquatic
eco-
hydroelectric
for assessing
inter-
factors
and
dams in the Amazon
have
a large flooded forest area where rapid mineralization of organics can take place under relatively high temperatures.
Accumulation
of
nitrogen
N2
ratios
in many part of
during recent past
actions
between
environmental
human communities.
observations
N20
isotope
(J. G. TUNDISIand E. WADA)
the purpose
vide excellent
lower
submitted;
light
as
be
hypolinion
et
isotopically
atmosphere
overturn
(YOH
showed
to
on
power and water supply.
These reservoirs in
Brazil are distributed in a range of geographic
regions with diverse human impacts and pro-
m),
hypolimnion
anoxic
(WADA
with
Japan
regard-
survey
depend
in hypolimnion,
(NO3-, N2O and so on) might
The number of reservoirs
tropical forests has increased
29.8
are
The nitrogen
nitrogen
systems
,
7).
processes
period
also depend on these factors.
5-5.
Gas exchange in tropical
(%0)
in
depth,
denitrification
of
organic
ecosystem
lake
max.
Preliminary
value
high 15N
might
mesotrophic
the overturn
of these processes
will cease.
the
process
(Fig.
during
N2O
lake
the extent of the anoxic layer, and the timing of
whole overturn of lake, when denitrification
fixa-
value
lake
accumulating
b).
this
values
km2;
and
the
in
the activities
Anabaena
by
nitrogen
surface
the
long
into
algae,
the
Lake
N2
low ƒÂ15N
1.4
nitrification
ed
biological
the ƒÂ15N
Kizaki,
area,
both
introduced
nitrogen
new
by
he
in
the
blue-green
the
Lake
(surface
During
was
characteristic
to
in
condition
fixed
traced
due
Suwa.
through
the
the
Lake
nitrogen
the
negligible.
Microcystis
VAN VUUREN
The amounts
of hypolimnetic
N2 and
released to the atmosphere
across the
enrichment
be
originally
by
of
13C
to
N-deficient
new
lake
the
seemed
photosynthesis
euphotic
ing
small,
DIC
phenomena
intense
that
very
remaining
KOIKE, REEDURGII, TUNDISI, YOSHINARI, YOSIIIOKA and
tree leavesand microalgaeand denseunder-
dur-
Kizaki
illustration
.
water
vegetation
of gas exchange
produce
in Lake
Suwa .
microanaerobic
sites
Gas Exchange
near
the
large
bottom
methane
The
the
basin.
It is
Rondonia.
km
km
with
reservoir
third
of
located
the
of
huge
amounts
trial
plants
long
depth
values
values
of
nitrogen
dam
of
processes.
sulfide-like
A
compounds
site
such
at
as
this
dam
the
was
time
(Fig.
construction,
Fig. 8.
easily
8).
sediments
of
with
-
hydrogen-
Thus
at
human
deforestation
Schematic
extent.
In coastal
detected
nitrogen
metabolism,
have been
Denitrification
is the lar-
reservoir.
release
of
(I. KoIKE)
inflow of nutrients from
region, microbial activ-
by
nitrification
smell
and estuar-
on
615N
reservoir
in coastal
effects
last for
gest gas evolving process within the nitrogen
cycle in the biosphere and is responsible
for
returning
fixed nitrogen to the nitrogen gas
phytoplanhigh
the
of
occurrence
denitrification
by
Such
commonly
in both the water column and the
of near-shore
environments
to a
considerable
isotope
caused
showed
areas
ities, including
gases
(POM)
was
suggesting
upper
of
stimulated
sediments
low ƒÂ13C
CO,
POM
+13%,
subsequent
This
mineralized
surface
from
matter
at least 3 years.
5-6.
Gas production
of
construction.
carbon
recorded.
ine environments
terres-
bubble
were
Due to the increasing
the populated coastal
the
loading
dramatically
-37%0.
of
The
at
construction
and
algae
by dam construction
deeper
from
and
nitrogen
of
km2.
the
the
dam
after
organic
to
1300
and
caused
to
anaerobic
materials
exhibited
recycling
m
the
aquatic
Velho,
width
of
of
year
Particulate
Port
materials
by
for
down
35
became
a
water
extends
area
organic
half
of
gases such as CO, CH,, N, and N,O.
Consequently, s15N of the remaining available
nitrogen became higher and low s13C values for
October
a maximum
is
biological
kton.
impact
and
Amazon
west
because
of
fillter
km
flooded
reservoir
collected
GFC
the
(TUNDIsI
in
the
has
flooded
studies.
the
high
reservoir
and
total
1989,
dam,
were
100
construction
July,
in
Samuel
a
time
the
(cutting and burning of forest), and sand mining with subsequent burial of plant materials in
downstream
areas, enhanced
the release of
where
with
constructed
dam
maximum
layers
In
reservoir,
emitted
(>30%)
The
150
The
the
are
biogenic
Samuel
is
20
of
bubbles
unpublished).
1988
over
of
concentrations
WADA,
a
surface
amount
275
in Ecosystems
illustration
environments,
tion.
Recent observations
rence of a close coupling
and denitrification
with the
Although
coastal
the
layer of
indicating the occurbetween nitrification
in sediments
are consistent
above view (NisHio et
production
of nitrogen
environments
nitrogen
of gas exchange
the surface
is the most active site of denitrifica-
budget
in Samuel
al., 1983).
gas from
has a significant
of the
dam.
system,
effect on
evolved
276WADA
nitrogen
long
, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSHINARI, YOSHIOKA and VAN VUUREN
gas
term
is rather
changes
hardly
be detected
spheric
reservoir.
Both nitrifying
the
capacity
near
shore
nitrous
Fig.
atmo-
bacteria
have
is mainly
nitrogen
waters
9.
large
of the
and denitrifying
of microbial
coastal
oxide
production.
In
of
as well
activity.
sites
ments.
as oxygen
for
nitrous
in
oxide
middle
of
sediments
and
the
effect
side
of
bottom
right
sediments
during
irrigation
of nitrifica-
(KOIKE and SORENSEN,
1988; SuMI and KOIKE,1990; KOIKE, 1990).
Figure 9 shows the possible micro sites
in
coastal
of
waters,
where
close
coupling
is
mainly
nitrous
of
responsible
for
oxide, a potent source
the
evolution
and
tion in the atmosphere.
nitrogen
column
biological
column
activity
gas
evolution
indicates
vertical
processes
indicates
of
benthic
on
the
the
injection
animals
in
coastal
and
profiles
profiles
of
(ALLER
of
oxygen
(JORGENSEN
and
estuarine
major
of
of ozone destruc-
of nitrous
the
the
the process
nitrification
and denitrification
is to proceed.
Both microbial nitrification
and denitrification
to the
Eutrophication
by accelerating
tion and denitrification
by the supply
production
Figure
oxide
can
the concentration
controlled
stimulates
Micro
and even
because
for nitrous
oxide
inert
content
environments,
of inorganic
sites
chemically
in atmospheric
environ
oxidants
, 1982).
Figure
(Umole•El-1)
REVSBECH
in
in
into
, 1985).
Gas
5-7.
Exchange
Stable isotope composition in nitrous
oxide
from
various
sources
(T.
it
YOSHINARI).
duction
is
and
important
biomass
N20 concentration
For
ples
the
fossil
burning,
and
N2O
the
and
were
of
quartz
sealed
Based
tive
isotope
values
can
The
and sink
gas
N20
in
in
from
the
450•Ž
and
N20,
and
for
the
24
hr
The 15
CO2
data
respec-
from
literature,
10)
global
shows
strengths
the ranges
land and ocean.
the
a qualitaand
(Fig.
source
in
spectrometry.
biogeochemistry
diagram
of atmospheric
was
CO,
1990).
N2
isotope
oceanic
of N20 in the atmosphere,
different
method
and
mass
N20
described.
and
N2
by
be
sam-
Subsequently,
at
ratios
N20
few
modified
carbon
of
schematic
a
and
the
chromatography
determined
and
nitrogen
(YosIIINARI,
18O/16O
the
in
the
to
tube
study
aspect
terrestrial
of the sources
and
N2O,
(1983).
graphitic
on
present
ous other environments.
diagram
envi-
of
both
and
by
in
budget
and oxygen
oceanic
of
quantitatively
presence
is to establish a broad database of the isotope
fingerprint of N20 in the atmosphere
and vari-
nitrogen
pro-
nitrification
combustion
by
MATSUO
purified
tively,
Schematic
relative
N2O
photolysis
of
collected
and
N/14N
Fig. 10.
as
and
fuel
the
atmosphere
YOSHIDA
product of biological nitrification.
The use of
the stable isotope signature of N20 as a tracer
this effort,
soil
composition
were
converted
Through
the
determination
gas is one of key elements in the nitrogen cycle
on the Earth since it is an intermediate
of
biological denitrification
as well as the by-
promises to provide the information which cannot be obtained
by the
conventional
approaches.
The long-term goal of this study
the
of
such
in
isotope
in
of
into
processes
decomposition,
the
o xygen
expanding
Also, this
insight
troposphere.
sources
processes.
and
upper
at the rate of
gain
different
denitrification
approximately
0.2-0.4%
annually
(BoUWMAN,
1990) is attributed
to release mainly due to
anthropogenic
to
of
ronments,
and a greenhouse
gas, which contributes
to the increase of average surface temperature of the Earth by absorption of infrared radiation.
The increase of
tropospheric
hoped
importance
Nitrous oxide (N2O) in the atmosphere
is a
natural source of stratospheric
NO, which is
in ozone chemistry,
277
in Ecosystems
of
of
(1)
N20
278
WADA, LEE, KIMURA, KOIKE, REEBURGH, TUNDISI, YOSHINARI, YOSHIOKA and
and the stratospheric sink, (2) the amount of
N2O reserved in each environment, and (3) the
range of nitrogen and oxygen isotope values of
N2O in the troposphere, land and ocean. The
source strengths of N2O from the land and
ocean, 8-13 and 4-6 Tg•yr-1, respectively, were
derived from the following consideration. The
estimated range of land origin N2O, which
includes the fluxes of N2O from microbial
processes in the soil, fossil fuel combustion and
biomass burning, was derived from the addition
of the stratospheric sink strength [11 Tg•yr-1
(CICERONE,
1989)] and annual rate of increase
[3-6 Tg•yr-1 (WEISS, 1981; RASMUSSEN
and
KHALIL,
1986)], less the total flux of oceanic N2O
, 4-6 Tg•yr-1. The latter was estimated from
the results of recent studies in the open ocean
(CLINEet al., 1987; BUTLER
et al., 1989) and the
contribution from the coastal environments,
which was assumed to be as much as the
amount of N2O from the open ocean.
The range of the nitrogen and oxygen isotope
values of N2O shown in this figure were derived
from the literature (KIM and CRAIG, 1990;
WAHLENand YOSHINARI,
1985; YOSHIDAand
MATSUO,
1983; YOSHIDA
et al., 1984; YOSHIDA
et
al., 1989;YOSHINARI
and WAHLEN,
1985) and from
the present study. Since various sources that
produce N2O by different mechanisms o
bined, the range for the N2O isotope values
from the land shown in this diagram is very
wide.
摘
要
生 態 系 に お け る ガ ス 交 換:
そ の 全 体 像 とケ ー ス ス タデ ィ
この 報 文 は,1990年8月28日
横 浜 市 で開 催 さ
れ た 国 際 生 態 学 会 の シ ン ポ ジ ウ ム"生 物 圏 ・大 気
圏 の 炭 素 ・窒 素 循 環"で
発 表 され た 論 文 を表 題 の
線 に 沿 っ て ま と め た も の で あ る。 先 ず 大 気 降 下 窒
素 化 合 物 の 生 態 系 へ の 供 給 や 炭 酸 ガ ス ・メ タ ン ・
窒 素 ガ ス ・亜 酸 化 窒 素 ガ ス の 生 態 系 か ら の 発 生 に
つ い て の 一 般 的 な 知 見 と考 察 を人 間 活 動,特
に化
石 燃 料 の 消 費 や 作 物 生 産 の 増 大 に 関 連 させ て 論 じ
た。 す なわ ち大 気 中 のCO2の
増 加 はC‑O‑Fe‑Sサ
イ クル と大 気 の 間 の 短 絡 に起 因 し,メ
タ ン ・亜 酸
化 窒 素 の 増 大 は有 機 物 の 増 産 に起 因 して い る。
VAN VUUREN
生 態 系 各 論 にお い て はい つ くか の 代 表 的 な場(ヒ
ース ラ ン ド
,水 稲 根 圏,ツ ン ド ラ とタ イ ガ,湖,
熱 帯 ダ ム湖,河
口 と沿 岸 域)お
よび 地 球 規 模 のN2
Oに 関 す る 大 気 ・生 態 系 相 互 作 用 に関 す る 最 近 の
成 果 を ま とめ,い
くつ か の場 に つ い て は模 式 図 を
提 示 した。
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(Authors: Eitaro WADA, Mitsubishi Kasei Institute of Life Sciences, Minamiooya , Machida,
Tokyo 194, Japan, Present address: Center for
Ecological Research, Kyoto University , 4-1-23,
Shimo sakamoto, Shiga Prefecture 520-01, Japan;
John A. LEE, School of Biological Sciences, University of Manchester, Williamson Building , Oxford
Road, Manchester M 139PL , U. K., Makoto KIMURA,
Gas Exchange
Faculty
of Agriculture,
kusa-ku,
Nagoya,
Ocean
Research
Institute,
15-1, Minamidai,
William
99775-1080,
of Alaska
Resources
University
State
State
Dapartment
for
Laboratories
Plaze,
12201-0509,
P. O.
Box
of Tokyo,
1-
164, Japan;
of Marine
Science,
Fairbanks,
Alaska
G. TUNDISI, Center
and Applied
S. P., Brazil;
Chi-
Isao KOIKE,
Tokyo
Fairbanks,
U. S. A.; Jose
Sao Carlos,
Center
University
Nakano-ku,
Engineering,
York
University,
S. REEBURGH, Institute
University
Hydric
Nagoya
Aichi 464- 01, Japan;
Ecology,
of Sao
Tadashi,
of
and
Paulo
U. S. A.; Takahito
New
Shinshu
Nagano
VUUREN, Centre
University,
390, Japan;
for Agrobiological
太 郎,三
菱 化 成 生 命 科 学 研 究 所,〒194東
南 大 谷11;現
Wageningen,
住 所:京
The
池 勲 夫,東
台1‑15‑1;吉
3-1-1,
Mat-
M. I. VAN
Res., P. O. Box
AA
Netherlands;
和 田英
京都 町 田市
都 大 学 生 態 学 研 究 セ ン タ ー,〒
屋 大 学 農 学 部,〒464‑01名
13560,
Asahi
Margret
14,6700
of
Wadsworth
Research,
509 Albany,
sumoto,
520‑01,滋
YOSHINARI, New
Health,
of Science,
of
School
CEP
281
in Ecosystems
賀 県 大 津 市 下 阪 本4‑1‑23;木
京 大 学 海 洋 研 究 所,〒164東
岡 崇 仁,信
村 真 人,名
古
古 屋 市 千 種 区 不 老 町;小
京 都 中野 区 南
州 大 学 理 学 部,〒390長
松 本 市 旭3‑1‑1)
Empire
York
Received:
6 December
YOSHIOKA, Faculty
Accepted:
22 May 1991
1990
野 県