HAL Id: hal-02751028
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Submitted on 3 Jun 2020
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Effects of temperature, drought and elevated CO2on N2O fluxes in an upland grassland ecosystem : interactions with plant and microbial community
structure.
Amélie Cantarel, Juliette Bloor, F Poly, Jean-François Soussana
To cite this version:
Amélie Cantarel, Juliette Bloor, F Poly, Jean-François Soussana. Effects of temperature, drought and elevated CO2on N2O fluxes in an upland grassland ecosystem : interactions with plant and micro- bial community structure.. NitroEurope 5th General Assembly and Open Science Conference, Office Fédéral de l’Agriculture. CHE., Feb 2010, Solothurn, Switzerland. �hal-02751028�
Effects of temperature, drought and elevated CO
2on N
2O fluxes in an
upland grassland ecosystem :
interactions with plant and microbial community structure
*Cantarel A., *Bloor J.M.G., #Poly F. & *Soussana J.F.
*Grassland Ecosystem Research Group, INRA Clermont-Theix, France; #LEM, CNRS-Université Lyon 1, France
To determine the direct and
indirect effects of climate change drivers on N2O fluxes
To assess
whether climate change modifies the influence of abiotic and biotic factors on N2O fluxes
N2O fluxes
Context
N2O fluxes Climate effects
(CO2,Temp,H2O)
Community production
Plant traits
Soil nutrients Microbial activity
indirect
direct indirect
uptake emission
Study aims
Materials et Methods Experimental design
Temperature + 3.5 °C
Summer drought -20% CO2 increase + 200ppm ([CO2]
= 600ppm) CLERMONT-FERRAND (350m)
CC Control THEIX (850m)
TT
Temperature
TDTD
Temperature + Drought
TDCOTDCO22 Temperature
+ Drought + Elevated CO2
A2 scenario predicted for Massif-Central in 2070 (IPCC)
Ecosystem: Acid grassland, light sheep grazing, no fertilizers
5 replicated experimental units per climate treatment
N2O measurements using closed static chambers and a photoacoustic gas analyzer (INNOVA)
Variation in N2O fluxes
Results
N2O fluxes (gN-N2O.m-2 .hr-1)
0 20 40 60 80 100 120
Soil temperature (°C) and WFPS (%)
0 20 40 60 80 C
T TD TDCO2
Soil temperature (°C) WFPS (%)
Mar.07 Jul.07 Nov.07 Mar.08 Jul.08 Nov.08 Mar.09
N2O fluxes (gN-N2O.m-2 .hr-1)
0 20 40 60 80 100 120
Soil temperature (°C) and WFPS (%)
0 20 40 60 80 C
T TD TDCO2
Soil temperature (°C) WFPS (%)
Mar.07 Jul.07 Nov.07 Mar.08 Jul.08 Nov.08 Mar.09
Mar.07 Jul.07 Nov.07 Mar.08 Jul.08 Nov.08 Mar.09
Results Effect of season on N2O fluxes
(pooled across treatments)
N2O fluxes showed significant seasonal variation :
In 2007 and 2008, N2O fluxes were higher both in spring compared to winter and in summer compared to spring
In 2008 N2O fluxes were lower in autumn compared with summer
Winter Spring SummerAutumn Mean seasonal N 2O fluxes ( µgN-N 2O.m-2 .h-1 )
0 10 20 30 40
2007 2008
Kruskall Wallis p<0.0001 Kruskall Wallis p<0.0001
N2O fluxes and climate change treatments
Results
Climate change treatments did not have a significant effect on annual N2O fluxes in 2007 or in 2008
No significant climate treatments effects were detected on seasonal N2O fluxes.
2007
C T TD TDCO2
Annual mean of N2O fluxes (µgN-N2O.m-2 .hr-1 )
0 2 4 6 8 10 12 14 16 18
2008
C T TD TDCO2
Anova ns Anova ns
2007
C T TD TDCO2
Annual mean of N2O fluxes (µgN-N2O.m-2 .hr-1 )
0 2 4 6 8 10 12 14 16 18
2008
C T TD TDCO2
Anova ns Anova ns
Abiotic factors and N2O fluxes
Results
No treatment differences in magnitude of N2O fluxes by soil temperature class (0-10, 10-15, 15-20, 20-25°C; Chi² = ns)
Significant treatment differences in number of N2O emission events by soil temperature class (Chi² test, p=0.03). No differences for uptake events
events in control treatment
events in warmed treatment
n.s n.s
Abiotic factors and N2O fluxes
Results
Significant treatment differences in number of N2O flux events by WFPS class (Chi² test, p=0.04)
No treatment differences in magnitude of N2O fluxes by WFPS class (20-60, 60-100%; Chi = ns)
More N2O emission events in control treatment
More N2O emission and uptake events in warmed treatment
Results
Positive effect of soil temperature (Spearman R: 0.643) and rainfall (Spearman R: 0.643) on N2O fluxes
Negative correlation between WFPS and N2O fluxes (R: -0.250)
Treatments R² Soil temperature WFPS Rainfall
C 18.65** ** ns ns
T 45.55** ns ** ***
TD 37.77** * * *
TDCO2 30.30** *** * ns
Climatic treatments seem to modify relations between N2O fluxes and abiotic factors.
Multiple regression analysis:
Ln(N2O) = a + b*ln(Soil temperature) + c*ln(WFPS) + d*ln(Rainfall)
Abiotic factors and N2O fluxes
Results
Coupled plant and flux measurements in April 2007/08
Mean N2O fluxes calculated for the month prior to biomass harvest (cut at 5cm)
Measures of biomass, community structure and species traits N2O fluxes
in April 2007
N2O fluxes in April 2008
p-value R p-value R
Biomass *** 0.599 ns -
Abundance of Festuca
arundinacea * 0.500 ns -
Leaf Nitrogen Content
(LNC) * -0.481 ** 0.606
Biotic factors and N2O fluxes
Interannual variation in the importance of vegetation on N2O fluxes may be linked to plant community dynamics
Coupled microbial and flux measurements in 2009
Targeted measurements in conditions favorable for N2O
emissions (high temperature and soil moisture)
Soil sampling following flux measurements
4 replications in time
Analysis of microbial activity (collaboration with LEM, Lyon)
Nitrification
Denitrification
NO2- NO N2O N2
Denitrification NH4+
N2O
NH3 NH2OH NO2- NO N2O N2 NO3-
N2O Nitrification
?
Materials et Methods Biotic factors and N2O fluxes
Results
Significant climate effects on N2O fluxes mirrored by patterns in nitrification and denitrification
Temperature effects on microbial activity may be related to microbial population size, community structure or
upregulation in enzymatic activity...
Biotic factors and N2O fluxes
0 0.5
1 1.5
2
C T TD TDCO2
Denitrification (µgN-N2O.g-1 .h-1 )
0 0.5
1 1.5
2
C T TD TDCO2
Nitrification (µgN-(NO2+NO3).g-1 .h-1 )
0 10 20 30 40 50 60 70 80
C T TD TDCO2
N2O fluxes (µgN-N2O.m².hr-1 ) Kruskall-Wallis, p=0.497 ANOVA, p=0.002 ANOVA, p=0.002
a
b b b
a
b b b
a
b b b
Results
No significant effects on size of denitrifying bacterial
populations (NirK gene) or on nitrifying bacterial populations (AOB gene)
Changes in microbial community? (work in progress)
Biotic factors and N2O fluxes
0.E+00 1.E+06 2.E+06 3.E+06 4.E+06 5.E+06 6.E+06 7.E+06 8.E+06
C T TD TDCO2
qPCRAOB (copies.gof dry soil-1 )
0.0E+00 5.0E+06 1.0E+07 1.5E+07 2.0E+07 2.5E+07
C T TD TDCO2
qPCRNirK (copies.gof dry soil-1 )
ANOVA n.s.
ANOVA n.s.
N2O fluxes showed limited responses to climate change drivers in our study system.
Greater responses might be expected in more productive grasslands.
N2O fluxes were correlated with soil temperature, WFPS and rainfall
Climate treatments appear to modify the relationship between N2O fluxes and abiotic factors
Relative contribution of different biotic factors in N2O flux variations remains to be determined.
Thank you for your attention!
Thanks to Deltroy Nicolas, Pichon Patrick, Guillaumaud Nadine, Moirot Caroline, Tardif Antoine and Jouve Amandine
