Mitigating N2O emissions - an ES delivered by soil microbes
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Mitigating N 2 O emissions - an ES delivered by soil microbes Sara Hallin Dept. Forest Mycology & Plant Pathology Swedish University of Agricultural Sciences, Uppsala ClimBEco Annual Meeting Aug 24-25, 2017 Höllviken
Transcript of Mitigating N2O emissions - an ES delivered by soil microbes
Mitigating N2O emissions - an ES delivered by soil microbes
Sara Hallin
Dept. Forest Mycology & Plant PathologySwedish University of Agricultural Sciences, Uppsala
ClimBEco Annual MeetingAug 24-25, 2017
Höllviken
« the microbial zoo »
Biomass in soil: 10 ton/ha• Bacteria 1-2 ton
Bacteria occupy <0.3% of pore space
Fungi: 10 – 100 m/gBacterial cells: 107 – 1010/g
”Species”: 103 – 104/g
N
“Leaky pipe” – N losses from soil
N2ON2O
Leaching
NH4+ NH2OH
NitrificationNO3
- NO2- NO N2O
N2
DenitrificationNO2
-
N2O
(Philippot & Hallin 2011, Trends Plant Sci.)
N2O
(Redrawn from Hallin et al. 2017 Trends Microbiol.)
NirS
NosZNORNirK
NO3- NO2
- NO N2O N2
N
OO
O
N
OO
O
N
OO
O
N
OO
O
N
OO
O
N
OO
O
NONON2
NON2ONONONO3- NO2- Denitrification
N
OO
O
N
OO
O
N
OO
O
N
OO
O
N
OO
O
N
OO
O
N N
N NN N
NONON2
NON2ONONONO3- NO2- Denitrification
ON N
ON NON N
NONON2
NON2ONONONO3- NO2- Denitrification
ON NON N
N N
N N
NONON2
NON2ONONONO3- NO2- Denitrification
nirKnirSnornosZ
652 genomes with denitrification genes:
SSU tree
(Graf et al, 2014 PLOS ONE)
• 30% have nosZwithout nir genes
• 24% have only nosZ –true N2O sinks
nirK+nosZ
70% of nosZ genomes have a complete denitrification pathway
(Graf et al, 2014 PLOS ONE)
Nearly 46% of 652 genomes potential N2O reducers
(Jones et al. 2013 ISME J)
Clade I
Clade II
Denitrification pathway
(Graf et al, 2014 PLOS ONE)
A new clade of the N2O reductase - N2O sink?
nosZ Clade I and II abundance in soils and other systems
Soil
WWTPWetland
Rice paddies Sediments
% o
f tot
al b
acte
rial c
omm
unity
(Jones et al. 2013 ISME J)
Clade IClade II
Clade I Clade II
(Orellana et al. 2014 mBio)
Reduction of N2O produced by inherent soil microbes by inocculating Dyadobacter fermentans into arable soils:
(Domeignoz-Horta et al, 2016 Soil Biol Biochem)
• nosZ II• not capable of denitrification• not capable of N2O production• N2O reduction coupled to growth
N2O
N2O reducing strain
No strain addedLOW inocculation levelHIGH inocculation level
First evidence that non-denitrifying N2O-reducers contribute to soil N2O reduction
Deni
trifi
catio
nen
d-pr
oduc
trat
io(N
2O/[
N2O
+ N
2])
Agricultural soils
(Domeignoz-Horta et al, 2016 Soil Biol Biochem)
In the soil
rN2O/r[N2+ N2O]Non-inoculated
rN2O/r[N2+ N2O]108 cells g-1 soil DW
rN2O/r[N2+ N2O]109 cells g -1 soil DW
Source
Sink
N2O s i n k i n d e
0.00.2
0.40.6
0.81.0
0.0
0.2
0.40.6
0.81.0
0.0
0.2
0.4
0.6
0.8
1.0
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
Capacity to consume N2O:
(Jones et al, 2014 Nature Climate Change)
Range of potential soil N2O sink capacity across 47 soils
Factors underlying N2O source or sink
Variable importanceStructural equation modeling
Factors underlying soil N2O source or sink
(Jones et al, 2014 Nature Climate Change)
Associated with plants
Treatments:• Sunflower• Barley• Control
• Soil A• Soil B
nosZ I
Soil A
nosZ II
Soil B
(Graf et al, manuscript)
(Graf et al, 2016 Soil Biol Biochem)
Soil A Soil B
nosZ
II:no
sZI r
atio
Niche differentiation between clade I and clade II
(Graf et al, manuscript)
Net
Rel
ated
ness
Inde
x (N
RI)
nosZ I nosZ I
nosZ II nosZ II
Soil A Soil B
Farming system & practices
14 long-term trials, +/-N
(Putz et al, manuscript)
Deni
trifi
catio
n en
d pr
oduc
t rat
io(N
2O/(
N2O
+N2)
)
nosZ/nir gene abundance
r2 = 0.49p < 0.0001
Long-term effects of N-fertilization on N2O reducers
***
Rela
tive
Abun
canc
e [%
]
*** **
Effect of site on the nosZ clade I community structure
Effect of site and fertilization on the nosZ clade II community structure**
* * **
% c
hang
efr
om u
nfer
tlize
d
nirS
nosZ InirK
NO3- NO2
- NO N2O N2
nosZ II
(Putz et al, manuscript)
Specific taxa change and abundance of denitrifiers increase
Community structure of N2O reducers:
N kg ha-1 y-1 0 150 0 120Soil C:NO3
- 0.64 0.70 0.55 0.50
NO3- NO2
- nir nosZNO2-NH4
+ nrfA NO N2O N2
(Schleusner et al, manuscript)
Long-term effects of cropping system on fate of nitrate
Denitrification
Dissimilatorty nitrate reduction to ammonium
(DNRA)
Nitrogen lossNitrogen retention
Cropping system overrule fertilization
C to nitrate ratio drives differences
Ley more DNRA activity and less N2O emissions, confirms gene data
DNRA bacteria : DenitrifiersN2O reducers : Denitrifiers
(Schleusner et al, manuscript)
Ecosystem scale
(Juhanson et al, 2017 SBB; Enwall et al, 2010 AEM)
• α diversity, abundance, comunity structure, assemblymechansims show nichedifferentiation
• Suggest biotic interactions drive nosZ clade II microbes
Spatial study of clade I and II nosZ communities across 44 ha
nirK abundancenosZI/nosZII
ON NON N
N N
N N
NONON2
NON2ONONONO3- NO2- Denitrification
Agricultural Diversification – Digging Deeper
Oscar and Lili LammFoundation
INRA, France:Laurent PhilippotDavid BruLuiz Domeignoz-HortaAymé Spor
Univ. Gothenburg:Philipp SchleusnerTobias Rütting
Microbial Ecology:Chris JonesDaniel GrafMartina PutzMaren EmmerichMing ZhaoMaria HellmanJaanis Juhansson
Awesome team Collaborators Funding
PhD position on fungal denitrification openingContact me: [email protected]
HI: Agricultural Diversification enhances Soil Biodiversity and EcosystemSustainability
(Bender et al. 2017. Trends Ecol Evol)
