Download AronsonDOE group meeting presentation

Impact
of
varied
precipita/on
and
N
deposi/on
on
grassland
soil
microbial
communi/es
and
GHG
flux
Emma
L.
Aronson
Allison
lab
UC
Irvine
Soil
Respira/on
(CO2)
• CO2
is
the
most
abundant
anthropogenic
greenhouse
gas
(GHG)
• CO2
is
responsible
for
most
global
warming
• In
soil,
CO2
released
by
microbial,
animal,
and
tree
root
respira/on
Methane
(CH4)
• Methane
(CH4)
responsible
for
>20%
of
global
warming
• Holds
25x
as
much
heat
as
carbon
dioxide
(CO2)
• 200x
less
CH4
in
the
atmosphere
than
CO2,
with
erra/c
increase
Methane
(CH4)
• Methanotrophs
‐
methane
oxidizing
bacteria
‐
need
oxygen
‐
dominant
in
unsaturated
soil
• Methanogens
‐
methane
producing
archaea
‐
cannot
live
in
oxygen
‐
dominant
in
saturated
soil
Nitrous
Oxide
(N2O)
• Responsible
for
~6%
of
global
warming
• Rising
due
to:
– Increased
fer/liza/on
of
agricultural
systems
– Increased
industrial
and
automo/ve
release
– N
leaching
and
deposi/on
because
of
1st
2
causes
Nitrous
Oxide
(N2O)
• Greater
N
fer/liza/on
and
deposi/on
on
soil
increase
N
cycling
• N
addi/on
s/mulates
increased
nitrifica/on
and
denitrifica/on,
which
both
release
N2O
16S
Bacterial
Community
Analysis
• 16S
gene
is
conserved
in
bacteria,
coding
for
part
of
the
ribosome
• Commonly
used
for
molecular‐based
OTU
iden/fica/on
• Used
to
build
phylogene/c
trees
of
microbial
communi/es
454
Sequencing
• Sequencing
bacterial
16S
• Same
procedure
as
we
are
doing
for
leaf
li\er
• 454
Allows
for
the
genera/on
of
long
read
lengths,
up
to
450bp
• No
need
for
cloning!
Quan/ta/ve
PCR
• Quan/ta/ve
PCR
(qPCR)
is
used
to
quan/fy
a
gene
of
interest
• In
this
case
I
will
focus
on
genes
for:
– Methanotrophy
(pmoA)
– N2O
produc/on
(nirS,
nirK
&
nosZ)
Hypotheses
• I
hypothesize
that
Loma
Ridge
treatments
have
changed
soil
microbial
communi/es
• Soil
moisture
&
inorganic
N
status
influence:
– Soil
respira/on,
– CH4
consump/on
rates,
and
– N2O
release
rates
– Bacterial
community
composi/on
Expected
Outcomes
Decreased
Rainfall
Control
Increased
Rainfall
Indicates
rate
of
CO2
and
N2O
release,
opposite
effect
on
CH4
consump/on
Indicates
level
of
soil
microbial
biodiversity
Expected
Outcomes
N
Added
N
N
N
N
Control
N
N
Indicates
rate
of
CO2
and
N2O
release,
opposite
effect
on
CH4
consump/on
Indicates
level
of
soil
microbial
biodiversity
Methods:
Greenhouse
Gas
Fluxes
• Measuring
CO2
flux
at
a
high
temporal
resolu/on:
– We
have
8
auto‐chambers
deployed
for
con/nuous
field
measurement
of
CO2
fluxes
– There
is
one
auto‐chamber
in
each
treatment
combina/on
sub‐plot
Methods:
Greenhouse
Gas
Fluxes
• Measuring
CO2,
CH4
and
N2O
fluxes
at
a
high
spa/al
resolu/on:
– Chamber
bases
implanted
in
all
48
sub‐plots
in
the
Loma
grassland
experiment
– Gas
flux
data
collected
with
chambers
weekly
to
monthly
– These
gas
samples
are
run
on
gas
chromatographs
for
CH4,
CO2
and
N2O
flux
Methods:
Soil
Microbe
Community
• On
gas
sampling
dates,
surface
soil
is
also
collected
and
frozen
in
the
field.
• I
will
study
soil
microbial
community
by:
DNA
Extrac/on
16S
PCR
qPCR
Nitrifiers
454
Sequencing
Methanotrophs
Denitrifiers
Results:
N
Treatment
• October
28,
2011,
measured
all
48
plots
• Increased
N2O
release
in
N
treated
plots
rela/ve
to
control;
no
impact
on
CO2
and
CH4
N2O
CO2
CH4
P < 0.077
P < 0.451
P < 0.288
Results:
H2O
Treatments
• October
28,
2011,
measured
all
48
plots
• Decreased
CO2
release
in
+
&
‐
H2O
treatment
plots
rela/ve
to
control
• No
impact
on
N2O
and
CH4
N2O
CO2
CH4
P < 0.574
P < 0.076
P < 0.860
Ini/al
Outcomes
Decreased
Rainfall
Control
Increased
Rainfall
Indicates
rate
of
CO2
release
Trends
were
not
seen
in
N2O
release
and
CH4
consump/on
Ini/al
Outcomes
N
Added
N
N
N
N
Control
N
N
Indicates
rate
of
N2O
release
Trends
were
not
seen
in
CO2
release
and
CH4
consump/on