Download Soil Organic Matter Pools and Fluxes in Response to Changes in

Soil Organic Matter Pools and Fluxes
SOIL CARBON DYNAMICS: IMPROVING MODELin Response
to
Changes
in
Temperature
OBSERVATION INTEGRATION
Serita D. Frey
Serita
D. Frey
University
of New
Hampshire
University of New Hampshire
• Background
• Observations from climate change experiments
• Highlight some of the challenges to
understanding and modeling soil carbon cycleclimate interactions (temperature, microbial
physiology, and N feedbacks)
• Research Needs (observations and modeling)
U.S. DOE (2008)
• Uncertainty in observational
data
• Variation in modeled NPP
• Differences in how Ts
represented
• Models don’t incorporate
processes important for soil
C stabilization/destabilization
Todd-Brown et al. (2013)
Modeling Soil Carbon Pools and Fluxes
DAYCENT soil organic matter model
Parton et al. (1987, 1994)
Historical and Emerging Views of Soil C Cycling
Schmidt et al., 2011
Soil Temperature
Jacobs et al. (2011)
Soil T increase of 0.037-0.049°C yr-1
Baker and Baker (2002)
Temperature Response of Soil C Flux
Chen and Zhuang (2013)
Temperature Response of Soil C Flux
Chen and Zhuang (2013)
Giasson et al., in review
1800
Soil respiration (g C m-2 yr-1)
1600
Soil Respiration in Response to 5°C Warming
Control
Heated
1400
1200
1000
800
600
400
200
0
2006
2007
2008
2009
Year
2010
2011
Soil Warming Stimulates the Nitrogen Cycle
Harvard Forest (Barre Woods)
Estimated increase in N availability: 27 kg N ha-1 yr-1
Butler et al. (2012)
Net Carbon Balance in Response to Soil Warming
Harvard Forest (Barre Woods)
Melillo et al. (2011)
Ecosystem Responses to Experimental Warming
Global meta-analysis of 85 studies
Soil respiration increased 12% on average
Wu et al., 2011
Short-term studies do not anticipate longer term responses
Changes in Carbon Release in Response to Warming
Heated vs. Disturbance Control, 1991-2003
% Change in Carbon Released ((H - DC)/DC) *100
Harvard Forest Soil Warming Study
30
20
10
0
-10
91-93 92-94 93-95 94-96 95-97 96-98 97-99 98-00 99-01 00-02 01-03
3 Year Running Means
Heated plots:
5ºC above ambient
% Change in Nirogen Mineralization ((H - DC)/DC) *100
Increases in Nitrogen Mineralization in Response to Warming
Heated vs. Disturbance Control, 1991-2003
160
140
120
100
80
60
40
20
0
91-93 92-94 93-95 94-96 95-97 96-98 97-99 98-00 99-01 00-02 01-03
3 Year Running Means
Melillo et al. (2002)
400
g C m-2 yr-1
Soil respiration (mg C m-2 hr-1)
450
Control
Heated
350
1600
1200
800
400
0
2006 2007 2008 2009 2010 2011
Hypotheses?
300
250
200
150
100
50
0
2007
2008
2009
2010
2011
2012
Research Needs
Observations
• Is there differential temperature sensitivity of various SOM compounds?
• What are the mechanisms underlying the reduced respiratory response
following long-term warming?
Modeling
• Better capture temperature responses, including “acclimation” of the soil C
flux in response to long-term warming
Modeling Microbes
DAYCENT soil organic matter model
Parton et al. (1987, 1994)
Manzoni et al. (2012)
Manzoni et al. (2012)
Temperature Response of Microbial Efficiency
Frey et al. (2013) Nature Climate Change
Frey et al. (2013) Nature Climate Change
Soil C Response to varying Microbial Efficiency
(DAYCENT)
Frey et al. (2013) Nature Climate Change
Manzoni et al. (2012)
Soil C Response to varying Microbial Efficiency
(Allison et al., 2010)
Soil C Response to varying Microbial Efficiency
(Weider et al., 2013)
Observations: 1250 Pg C
CLM4cn: 691 Pg C (r = 0.55)
DAYCENT: 939 Pg C (r = 0.53)
CLM microbial model: 1310 Pg C (r = 0.71)
Divergent model responses of global soil C pools
Steady state soil C pools
DAYCENT
CLM4cn
CLM microbial model
Warming scenario (+4.8°C by 2100)
Wieder et al. (2013)
Research Needs
Observations
• Is there differential temperature sensitivity of various SOM compounds?
• What are the mechanisms underlying the reduced respiratory response
following long-term warming?
• What are the key regulators of microbial C use efficiency?
Modeling
• Better capture temperature responses, including “acclimation” of the soil C
flux in response to long-term warming
• Incorporate microbial physiology and other soil biogeochemical
mechanisms into ESMs
Coupled Biogeochemical Cycles:
Nitrogen Deposition and Soil Carbon Storage
Changes in the woody biomass carbon pool
of northern temperate and boreal forests
Terrestrial biomass C sink: 0.68 ± 0.34 Pg
Myneni et al. (2001)
Galloway et al. (2004)
Janssens et al. (2010)
Carbon stocks (kg m-2)
Carbon Stocks in Control and Nitrogen Fertilized Plots
40
20-30 kg C kg-1 N added
Soil sink: 59-87% of total
Hardwood
30
Wood
Litter
Fine roots
Forest floor
Mineral soil
20
10
0
Carbon stocks (kg m-2)
1
40
2
3
Pine
30
20
10
0
0
50
150
N Addition (kg N ha-1 yr-1)
Frey et al. (Nature Geoscience, in prep)
Soil C stock (kg m-2)
Soil Carbon Stocks
24
Hardwood
20
16
25 kg C / kg N**
Oe
Oa
0-10
10-20
20-30
30-40
10 kg C / kg N*
12
8
4
0
Soil C stock (kg m-2)
0
24
50
150
Pine
20
16 kg C / kg N*
5 kg C / kg N*
50
150
16
12
8
4
0
0
Nitrogen addition (kg ha-1 yr-1)
*Forest floor only
**Forest floor plus mineral soil
Carbon Sequestration in Temperate Forests
per unit Nitrogen Added
Study location
N. America & Europe (9 sites)
Europe (121 plots)
Finland, Sweden (15 sites)
Michigan, USA (4 sites)
Meta-analysis (20 experiments)
Deciduous stand (MA, USA)
Deciduous stand (MA, USA)
Pine stand (MA, USA)
Pine stand (MA, USA)
1 Study
duration (yr)
1-3
40
14-30
10
-20
20
20
20
Nitrogen inputs
(kg ha-1 yr-1)
4-58
2.8
30-200
30
28-300
50
150
50
150
Carbon response (kg C kg-1 N)
Trees
Soil
Total
ǂ
25
21
46
δ
11
15
26
25
11
26
0
14
14
£
-19
-10
10
20
5
25
30
-10
16
6
-7
5
-2
Reference
Nadelhoffer et al. (1999)
de Vries et al. (2006)
Hyvönen et al. (2008)
Zak et al. (2008)
Janssens et al. (2010)
This study
This study
This study
This study
Growing consensus that the soil C pool is as or more
responsive to N additions than is NPP
Frey et al. (Nature Geoscience, in prep)
Litterfall mass (g C m-2)
Carbon Inputs to Soil
Hardwood Stand
6000
4000
Control
50 kg N/ha/yr
Hardwood
150 kg N/ha/yr
2000
0
1989 1991 1993 1995 1997 1999 2000
Litterfall mass (g C m-2)
With N fertilization:
Pine Stand
6000
Litterfall
Root biomass
Root productivity
Root respiration
Pine
?
C inputs not dominant mechanism
(~10-30%)
4000
2000
0
0
1989 1991 1993 1995 1997 1999 2000
Year
OEA
M 0-10
M 10-20
Root kg C.ha-1
1000 2000 3000 4000
HC
HLN
HHN
PC
PLN
PHN
Soil respiration (µmol m-2 s-1)
Carbon Outputs
With N fertilization:
Soil respiration
12
10
Control
N50
N150
8
y = 1.1285e0.0904x
y = 1.2592e0.0768x
6
4
•  Soil respiration consistently lower
•  Litter and wood decay suppressed
y = 1.2478e0.0641x
2
0
Contosta (2011)
100
5
10
15
Temperature (°C)
20
25
90
80
70
Mass remaining (%)
g60
n
i
in50
a
m
e 40
R
%30
C
W
WN
20
N-2 y
10
N-20 y
0
0
12
Months
Magill and Aber (1998)
Time (mo)
Photo by
K. Dudzik
16
24
Organic Matter Chemistry
Pyrolysis-GCMS of forest floor material (hardwood stand)
0
50
150
Frey et al. (Nature Geoscience, in prep)
Research Needs
Observations
• Is there differential temperature sensitivity of various SOM compounds?
• What are the mechanisms underlying the reduced respiratory response
following long-term warming?
• What are the key regulators of microbial C use efficiency?
• Need better estimates of global soil C stocks
• Priming
Modeling
• Better capture temperature responses, including “acclimation” of the soil C
flux in response to long-term warming
• Incorporate microbial physiology and other biogeochemical mechanisms
into ESMs
• Incorporation of N feedbacks on soil C storage (N deposition rates
predicted to double by 2050)
• Priming
Soil Respiration Components
Rautotrophic
RG
Rrhizosphere
RG
Rheterotrophic
RR
RM
RMF
RP
RL
RS
Modified from Hopkins et al. (2013)