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The sensitivity of vegetation and soil processes to drought and warming and the
consequences for C sequestration Bridget Emme+, Alwyn Sowerby, Andy Smith, Miles Marshall, Rob Mills and Susie van Baarsel (Centre for Ecology and Hydrology, Bangor); Davey Jones, Eva Koller (Bangor University); Claus Beier, and Klaus Larsen (DTU); Inger Schmidt (Copenhagen University);Albert Tietema, Sharon Mason and Daan Asscheman (University of Amsterdam); GiovanbaLsta De Dato, Paolo De Angelis (DISAFRI, Uni of Tuscia); Edit Kovacslang, Gyorgy Kroel-‐Dulay, Janos Garadnalk
(Hungary Academe of Sciences); et al…..
Short and long term effects of climate change
• Short term direct effects:
– ANPP and SR
• Longer term indirect effects, asymmetry and ‘carry-over’ effects due to:
– Response Tme of pool longer than length of event – Ecological changes due to change in plant and soil
community – Lack of reweLng due to precipitaTon pa+erns and
runoff due to a change in soil physical properTes
Pre-disposing and modulating factors? • Ambient climate (i.e. current limiting factors)
• Vegetation characteristics
• Stability vs dynamic • Pre-conditioning or exacerbating events (e.g.
insect infestation) • Plant functional types or strategies
• Soil characteristics which affect onset and modulation
• Soil parameters which affect plant available water
• Soil functional types or strategies
What are the conclusions of past syntheses? Rustad et al. 2001 ;Walter et al. 2002; Knapp et al. 2008; Wu et al. 2011 etc:
• C fluxes
– ReducTon in precipitaTon reduces ANPP and biomass by ca. 20-‐30%
– Warming increases biomass and TNPP by ca. 20-‐30% • Pre-disposing or interfering factors
– No effect of experimental approach or length of experiment – Variable effect of ambient climate/limiTng factors – Physiological traits indicates predicTve direcTon of change for
ca. 80% of species – No other consistent factors idenTfied
But few experiments > 5 years long
The Increase network
• 7-‐12 year long experiments = long term indirect effects
• Use a common approach so reduces interference from methodology
• Modest treatments ( we didn’t want to kill anything immediately) Ø -‐20% rainfall during main growing season
Ø +0.5 –to 1 oC • ContrasTng sites
INCREASE field sites across
Europe
www.increase-infrastructure.eu
Summer drought
IR reflection
Night time warming Timer Rain censor
Control
The experimental design
-- 20 m2 plots -- 3 replicates for each treatment -- since 1998/2001 to 2012
Climatic range of the site network
wet dry
(Penuelas et al. 2007)
Precip/(2 Temp)
cold hot
Our questions
• Are soil or plant biota more sensitive to climate change in the long term?
• What are short and long term implications for C sequestration?
• Can this be predicted from ambient climate?
• Are there other pre-disposing or interfering factors which influence outcome?
Cold Hot
Decomposition
High
Low
Wet Dry
Greater relative sensitivity of ANPP relative to decomposition in more arid
climates (Ågren et al. 1996)
Plant production
High
Low
Aridity index
Sens
itivi
ty
Hypotheses
Greater sensitivity of decomposition relative to plant production in northern latitudes
(Kirshbaum 1995)
Plant production
Decomposition
Temperature
Sens
itivi
ty
Net C loss
Net C loss
Warming Drought
Cold Hot
Decomposition
High
Low
Wet Dry
Greater relative sensitivity of ANPP relative to decomposition in more arid
climates (Ågren et al. 1996)
Plant production
High
Low
Aridity index
Sens
itivi
ty
Hypotheses
Greater sensitivity of decomposition relative to plant production in northern latitudes
(Kirshbaum 1995)
Plant production
Decomposition
Temperature
Sens
itivi
ty
Net C loss
Net C loss
Warming Drought
Measurements
• Biomass • Annual pin poinTng
• Litterfall • Li+erpots or from sensecing material
ANPP = ∆ above-ground biomass + litterfall
• Soil respiration • IRGA
Response after 7-12 years
Xeric sites; Hungary and Italy
0
50
100
150
200
250
300
350
400
450
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
Hungary: Biomass
C
D
W 0
10
20
30
40
50
60
70
80
90
100
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
Hungary: Li2er
C
D
W
0
20
40
60
80
100
120
140
160
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
Hungary: Soil respira8on C
D
W
Xeric (Hungary and Italy)
Change rela8ve to control
Drought Warming
Biomass -‐28% +18%
ANPP -‐34% +32%
SR +2% +5%
ANPP more responsive than soil respiration Equal sensitivity to drought and warming
Acclimation or carry-over effects?
y = -‐4.8706x + 9748.6 R² = 0.1667
y = -‐7.3091x + 14683 R² = 0.38169
-‐80
-‐60
-‐40
-‐20
0
20
40
60
80
100
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010 g/
m2
Hungary: ANPP
D-‐C
W-‐C
y = -‐1.2582x + 2525.6 R² = 0.6572
y = -‐1.176x + 2365.3 R² = 0.60684
-‐5
0
5
10
15
20
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
Hungary: Soil respira8on
D-‐C
W-‐C
Treatment effect relative to control over time
Response after 7-12 years
Mesic site; Netherlands
Mesic (Netherlands)
Change rela8ve to control
Drought Warming
Biomass -‐21% +13%
ANPP -‐15% -‐7%
SR -‐22% +6%
0
200
400
600
800
1000
1200
1400
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
NL: Biomass
C
D
W
0 20 40 60 80 100 120 140 160 180
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
NL: Li2erfall
C
D
W
0
50
100
150
200
250
300
350
400
450
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
NL: SR
C
D
W
Vegetation and soil respond in parallel More responsive to drought
Acclimation / carry over effect only observed in soils
-‐250
-‐200
-‐150
-‐100
-‐50
0
50
100
150
200
250
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
NL: ANPP
D-‐C
W-‐C
R² = 0.51158
R² = 0.78711
-‐120
-‐100
-‐80
-‐60
-‐40
-‐20
0
20
40
60
80
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
NL: SR
D-‐C
W-‐C
Treatment effect relative to control over time
Response after 7-12 years
Mesic site + pests; Denmark
Calluna Dieback Due To Heather Beetle (DK)
Mesic + pest (Denmark)
0 100 200 300 400 500 600 700 800 900
1000
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
DK: SR
C
D
W
0
200
400
600
800
1000
1200
1400 1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
DK: Biomass
C
D
W
0
100
200
300
400
500
600
700
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
DKs: Li2er C
D
W
Change rela8ve to control
Drought Warming
Biomass -‐69% -‐30%
ANPP -‐28% -‐1.3%
SR -‐19% -‐1.7%
Vegetation and soil respond in parallel (as in NL) More responsive to drought (as in NL)
Drought exacerbated by pest outbreak (x2 NL)
Acclimation / carry over effects differ between vegetation and soil
R² = 0.36224
R² = 0.25591
-‐300 -‐250 -‐200 -‐150 -‐100 -‐50 0 50 100 150
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
DKs: ANPP
D-‐C
W-‐C
R² = 0.16692
R² = 0.17318
-‐160 -‐140 -‐120 -‐100 -‐80 -‐60 -‐40 -‐20 0 20 40
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
DK: SR
D-‐C
W-‐C
Treatment effect relative to control over time
Response after 7-12 years
Hydric site; UK
Hydric (UK)
Change rela8ve to control
Drought Warming
Biomass +9% -‐1%
ANPP -‐11% -‐3%
SR +9% +8%
0
1000
2000
3000
4000
5000
6000
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
UK: Biomass C
D
W
0
50
100
150
200
250
300
350
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
UK: Li2er
C
D
W
0
200
400
600
800
1000
1200
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
UK: SR
C
D
W
Vegetation and soil respond in opposite directions
Responsive to both drought and warming
Ongoing positive carry-over in soil responses
-‐2000
-‐1500
-‐1000
-‐500
0
500
1000
1500
2000
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
g/m2
UK: ANPP
D-‐C
W-‐C
-‐200 -‐150 -‐100 -‐50 0 50
100 150 200 250
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
gC/m
2
UK
D-‐C
W-‐C
Treatment effect relative to control over time
Analysis cross-sites
Does the aridity index or MAT provide any predictive power?
ANPP response is well predicted by aridity index
-‐60
-‐50
-‐40
-‐30
-‐20
-‐10
0
10
20
0 20 40 60 80 100 120
Chan
ge irela8
ve to control (%)
Gaussen aridity index
Change in ANPP in response to drought along an aridity gradient
ANPP
SR is not; response appears to be decoupled from ANPP
-‐50
-‐40
-‐30
-‐20
-‐10
0
10
20
0 20 40 60 80 100 120
Chan
ge irela8
ve to control (%)
Gaussen aridity index
Change in ANPP and SR in response to drought along an aridity gradient
ANPP
SR
ANPP response to warming is related to MAT
-‐5
0
5
10
15
20
25
30
35
40
5 7 9 11 13 15 17 Chan
ge in biomass rela8
ve to
con
trol (%
)
Change in ANPP in response to warming along a MAT gradient
ANPP
SR responds in opposite direction
-‐10
-‐5
0
5
10
15
20
25
30
35
40
5 7 9 11 13 15 17
Chan
ge in biomass rela8
ve to
con
trol (%
)
Change in ANPP and SR in response to warming along a MAT gradient
Conclusions • Drought
• Drought reduced ANPP by 11-‐47% with greatest sensiTvity in most xeric sites but had maximum effect on SR in sites mid-‐range of aridity gradient (-‐22 -‐ +9%)
• Loss of carbon will be greatest at the extremes of aridity gradient
• Warming • Warming increased ANPP by 0 – 32%with greatest sensiTvity in warmer sites but had most effect on SR in colder sites (-‐2 -‐ +8%).
• More carbon stored in warmer sites and less in colder
• Vegetation and soil responses to climate treatments are decoupled in their responses and this is increasing over time due to carry-over effects
• Why? Direct change in soil communities and soil structure is at least one explanation
Thanks to the many funders over the years – EU and national
Questions?
Revisiting hypotheses
Greater relative sensitivity of ANPP to decomposition to drought in drier climates (Ågren et al. 1996)
Yes
Greater relative sensitivity of decomposition to ANPP in response to warming in northern latitudes (Kirshbaum 1995)
Decomposition is more sensitive than ANPP in northern sites but unexpectedly large positive effect of warming on ANPP in southern sites
