soil C:N:P stoichiometry as a means to constrain
decomposition
Nick Ostle, Niall McNamara, Eva Tregidgo and Richard Bardgett
Dynamic Global Vegetation Models (DGVMs)
Simulate fluxes of carbon, water and nitrogen along with changes in the
vegetation dynamics, within an integrated system.
light
succession
fire
climate
CO2
soil
GCM
Cox et al. 2000 (Nature)
Climate input:
?
Precip,
s
i
s
PAR,
he Tair, RH
Carbon Fluxes in DGVMs
GPP1
GPP2
Ra2
Needleleaf
hy
Ra1
t
n
y
s
o
t
o
h
p
f
o GPP
R
n
o
i
Broadleaf
t
a
GPP3 Ra3
l
PFT (H1, FRACr1e,
LAI1) or
po
C3
he
t
grass
n
L1
it o
wood
RH
ra
i
p
s
e
r
l
i
so
Soil layer (Tsoil, Cstore, H2O)
is
4
a4
GPP5
no
vegetation
5 PLANTWFUNCTIONAL TYPES: COMPETING, INTERACTING
1 GLOBAL SOIL TYPE
Ra5
C4
grass
L4
Process studies
Rate of loss of CO2 from soil =
k x Cstored x fH2O x Q10temp/10
=2
Propose variable Ecosystem Q10’s
Soil Functional Types (SFT’s)
Case for soil function types (SFTs)
Large stocks of C in high latitude soils
High latitude soils will warm the most
Experimental evidence on Q10 variability
QUERCC: focus on organic
soils.
ECOSSE
Evidence of P limitation during forest decline phase
Significant increase in humus N:P and C:P with increasing age at all sites
>600,000 yrs
14,000 yrs
>22,000 yrs
Wardle, Walker and Bardgett (2004) Science.
14,000 yrs
4,100,000 yrs
>600,000 yrs
Peat respiration experiment
Objective: To compare respiration rates in peat soils from UK and European
sites in relation to C:P, N:P, C:N stoichiometry and abiotic conditions.
Great Dun Fell (England)
54º 65’N 2º 45’W
Altitude: 848 m
Peat layer: 2-3 m
Jyvaskyla (Finland)
62º 11’ N, 25º 40’E
Altitude: 165 m
Peat layer: < 0.5 m
Auchencorth Moss (Scotland)
55º 47’N 3º 14’W
Altitude: 270 m
Peat layer: 0.6 m
Plynlimon (Wales)
52º 26´N 3º 46’W
Altitude: 648 m
Peat layer: 1-2 m
Moor House Bog (England)
54º 42’N 2º 18’W
Altitude: 290 m
Peat layer: 2-3 m
Samples under incubation
Moor House (England)
54º 42’N 2º 18’W
Altitude: 290 m
Peat layer: 1-3 m
Xistral (Spain)
42º 48’N 8º 6’W
Altitude: 1039 m
Peat layer: 2 m
Sites in this study (7)
Sites recently sampled (3)
SITE
C:P
N:P
C:N
Moor House Bog
984
32
31
Moor House
641
24
26
Auchencorth Moss
442
21
21
Finland
427
13
32
Great Dun Fell
361
19
19
Plynlimon
351
18
19
Xistral, Spain
275
13
21
Mere Bleu Canada, Bonanza Creek Alaska, Caithness, Gallway
Eco-stoichiometric framework
: to explain peat C temperature sensitivity
WET
Soil Q10 (exp.)
Soil respiration
DRY
15oC
10oC
5oC
stoichiometric limitation (C:N, C:P)
Earth Respiration System
controlled
temperature
rooms
4oC
10oC
● Automated CO2, CH4 and N2O measurements
15oC
● Measure 32 soils simultaneously
● Can make repeated measurements over time
● Constant or variable temperature
20oC
20oC
15oC
10oC
4oC
30
-1
40
20
10
μ g CO2-C g dry wt peat
30
-1
60% WHC
50
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
20oC
15oC
10oC
4oC
0
4oC
0
100% WHC
50
40
20
10
μg CO2-C g dry wt peat
60
60
7
6
5
4
3
2
1
0
3
R2 = 0.78
P < 0.05
R2 = 0.4
P > 0.05
60% WHC
100% WHC
2
Q10
Q10
peat C:P and respiration Q10 values
1
0
0
250
500
C:P
750
1000
0
250
500
C:P
750
1000
“The temperature sensitivity of peat SOM to decomposition increases with increasing C:P”
3000 m
PERU ANDES 2007
60
-1
μg CO2-C g dry wt soil
Soil cores collected along 3 (so far of 14)
altitudinal gradients with variable C:P and N:P
y = 91.894e-0.5045x
R2 = 0.9729
50
40
30
20
10
0
10 oC
15 oC
20 oC
25 oC
1500 m
1000 m
-1
μg CO2-C g dry wt soil
7
y = 10.767e-0.5259x
R2 = 0.96
6
-1
μg CO2-C g dry wt soil
16
14
y = 24.29e-0.5604x
R2 = 0.98
12
10
8
6
4
2
5
4
0
10 oC
15 oC
20 oC
25 oC
3
2
1
0
10 oC
15 oC
20 oC
25 oC
In collaboration with: Patrick Meir & Yadvinder Malhi
● CO2 & CH4 flux measurements insitu on 30 islands with variable C:P
and N:P.
N:P
SWEDEN
● Laboratory incubations under
different temperature ranges.
40 yr
5300 yr
time since disturbance
NEW ZEALAND
● Laboratory incubations under
different temperature ranges.
N:P
● Nutrient assays on soils
under incubation with different
temperature ranges.
chronosequence stage
Examining the temperature sensitivity of
different soil carbon pools
→ Developing methods to parameterise 3
pool organic soil models
● Size fractionation
● Density fractionation
● Chemical fractionation
Eva Tregidgo PhD “Organic Soil Carbon Fractions”
Examination of soil microbial and C pools at experimental end point
4oC
10ooC
10
C
15oC
20oC
PLFA microbial biomass
Respiration function
“Examining the temperature sensitivity
of different soil C pools
Nutrients (C, N, P)
microbial communities
All treatments → 10 oC
“soil fractions (Eva Tregidgo)”
carbon quality
Eco-stoichiometric framework
: to explain peat C temperature sensitivity
WET
Soil Q10 (exp.)
Soil respiration
DRY
15oC
10oC
5oC
stoichiometric limitation (C:N, C:P)
SO,
Organic soil stoichiometry experiments on-going and extended to other soil
types e.g. tropical soils.
Development of meaningful measures of organic soil C pools for modelling
Looking to expand capability for soil Q10 studies with our Earth Resp System
Continued contribution of benchmark data for ECOSSE and Roth-C for JULES
development.