HAL Id: hal-02812839
https://hal.inrae.fr/hal-02812839
Submitted on 6 Jun 2020
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Long-term effects of climate change drivers
(temperature, drought and elevated CO2) on an upland grassland ecosystem
Amélie Cantarel, Juliette Bloor, Jean-François Soussana
To cite this version:
Amélie Cantarel, Juliette Bloor, Jean-François Soussana. Long-term effects of climate change drivers (temperature, drought and elevated CO2) on an upland grassland ecosystem. ACCAE, Oct 2010, Clermont-Ferrand, France. 2010. �hal-02812839�
Long-term effects of climate change drivers (temperature, drought and CO
2) on an upland
grassland ecosystem
Cantarel A., Bloor J.M.G. & Soussana J.F.
Grassland Ecosystem Research Group (UREP), INRA Clermont-Theix, France
http://www.clermont.inra.fr/urep/accae
Introduction
N2O fluxes N2O fluxes Climate effects
(CO2,Temp,H2O)
Community production
Plant diversity
Soil nutrients Microbial activity
uptake emission
Current climate models predict
global temperatures
Changes in regional patterns of rainfall
greenhouse gases production
Climate change has direct and indirect effects on
Plant community production
Plant community diversity
GES emissions
Long term effects of climate change remain unclear
How do climate change drivers affect grassland production (short and long term effects)?
Do plant biomass patterns match changes in species diversity or/and functional diversity?
How are trace greenhouse gases (N2O fluxes) impacted by climate change drivers?
Introduction Study aims
ACCAE 2010
Materials et Methods Experimental design
Temperature + 3.5 °C
Summer drought -20% CO2increase + 200ppm ([CO2] = 600ppm) CLERMONT-FERRAND (350m)
C C Control THEIX (850m)
T T Temperature
TD TD Temperature
+ Drought
TDCOTDCO22 Temperature
+ Drought + Elevated CO2
A2 scenario predicted for Massif-Central in 2080 (IPCC)
Ecosystem: upland grassland, light sheep grazing, no fertilizers
5 experimental units per climate treatment
Materials et Methods
Annual biomass production: sum of the April and October biomass per experimental unit
Species diversity: Shannon-Weaver, Equitability indices based on April cut
Functional diversity: proportion of grasses, legumes and forbs on annual biomass
N2O measurement with closed static chambers and a photoacoustic gas analyser (INNOVA)
ACCAE 2010
Effects of warming varied over time: positive effects in 2006 but negative effects in 2008 and 2009
Results Aboveground biomass production
Results
ACCAE 2010
Biomass tended to decrease in response to summer drought (but only significant in 2009)
Aboveground biomass production
Results
Positive effect of elevated [CO2] after three years of climate change
Aboveground biomass production
Significant effect of warming on functional diversity after 3 years of climate change
ACCAE 2010 Results
No effect of climate drivers on Shannon-Weaver and equitability indices
Plant diversity
negative impact on grasses
positive impact on legumes
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 C 80
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 C 80
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
N2O fluxes and climate change treatments
Results
Warming had a positive effect on annual N2O fluxes in 2007 (same tendency in 2008)
ACCAE 2010
2007 2008
ANOVA P<0.05 ANOVA ns
Results
Positive effect of soil temperature (Spearman R: 0.643) and rainfall (Spearman R: 0.563) 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** * * *
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
Climate change drivers have different effects on plant biomass production
Warming appears to be the most important climate change driver for this cool upland system
Elevated [CO2] effects are progressive in time
Limited summer drought may be related to ambient weather conditions
No change in species diversity but changes in functional diversity after 3 years of climate change
Decrease in grass abundance under warming mirrors patterns in plant biomass
ACCAE 2010 Conclusions – Part 1
Conclusions – Part 2
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
Long term studies are critical for detecting
progressive effects of climate change on ecosystems
Thank you for your attention!
Thanks to Deltroy Nicolas, Pichon Patrick, Tardif Antoine and Jouve Amandine
