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The impact of soil properties on C stocks
and mineralization rates of three
deciduous forest sites
Marion Schrumpf1, Klaus Kaiser2, Tryggve Persson3,
Matthias Grabe2, Ingrid Kögel-Knabner4, Mats Olsson5
1Max-Planck-Institute for Biogeochemistry, Jena, Germany
2Department of Soil Science and Soil Biology, University of Halle, Germany
3Department of Ecology and Environmental Research, Swedish University of Agricultural
Sciences,Uppsala, Sweden
4Department of Soil Science, TU Munich, Weihenstephan, Germany
5Department of Forest Soils, Swedish University of Agricultural Sciences, Uppsala, Sweden
Outline
• Background and project aims
• Study sites, sampling scheme and soil analyses
• Correlations between soil properties and
mineralization rates
• Summary and conclusion
Background
Decomposition rates of SOM depend on:
- environmental factors (temperature, soil moisture)
- chemical composition of OM
- degree of physical protection e.g. in aggregates
- formation of organo-mineral complexes
• mainly with clay-size particles
• Al and Fe oxides and hydroxides
Aims and research questions
How does the association of organic matter with
minerals affect mineralization rates and thus soil
carbon storage?
We expect to find lower mineralization rates at sites
- with a large contribution of MOM to total C
- with larger clay and pedogenic oxide contents
Study sites
Soroe
Hainich
Hesse
Study sites
Hainich (D)
Beech forest (National Park)
Location: 51°04´N, 10°27´E
Stand age: ~250 years
Tree height: 23 m
Stem density: 334 stems ha-1
Eutric Cambisol
Precipitation: 800 mm a-1
Mean temperature: 8 °C
Study sites
Hesse (F)
Beech/oak forest
Location: 48°40´N, 7°05´E Stagnic Luvisol
Stand age: 40 years Precipitation: 820 mm a-1
Tree height: 13 m Mean temperature: 9.2 °C
Stem density: 3 000 stems ha-1
Study sites
Soroe (DK)
Beech forest
Location: 55°29´N, 11°38´E Gleyic Cambisol
Stand age: 80 years Precipitation: 660 mm a-1
Tree height: 25 m Mean temperature: 8.2 °C
Stem density: 430 stems ha-1
Soil sampling and analyses
10
Soil sampling:
9
8
7
6
5 A1
4 B2
3 C3
2 D4
E5
1
F6
G7
- 10 cores per site
H8 -1
-2
I9
-3
J10
K11
L12
M13
N14
O15
P16
Q17
R18
S19
- 0-5, 5-10, 10-20, 20-30 … cm
T20
U21
V22
W23
X24
Y25
Soil analyses
• C concentrations and stocks
• mineralization rates
(lab, 15°C, 60%WHC)
• density fractionation
(1.6 g cm-3, FPOM, OPOM, MOM)
• particle size distribution
• Fe and Al oxides and hydroxides
(oxalate- and dithionite-extractable)
Results – C concentrations
-2
C concentration [g kg]-1]
C stock [kg C m
0 2 4 6 8
8 10
10
0
10
Soil depth [cm]
20
30
40
Hainich
50 Hesse
60
Soroe
Results – Mineralization rates topsoils
0-5 cm soil depth r = -0.67
p < 0.01
0.5
Mineralization rate [g CO 2 g-1 soil C]
0.4
0.3
0.2
0.1
Hainich
Hesse
Soroe
0.0
0 100 200 300 400 500 600 700
Clay content [g kg-1]
Results – Mineralization rates topsoils
0-5 cm soil depth r = -0.59
p < 0.01
Mineralisation rate [g CO2 g C]
-1 0.5
0.4
0.3
0.2
0.1
Hainich
Hesse
Soroe
0.0
0 20 40 60 80 100
MOM [%]
Results – MOM topsoil
0-5 cm soil depth r = 0.64
80 p < 0.01
60
MOM [g kg ]
-1
40
20
Hainich
Hesse
Soroe
0
0 100 200 300 400 500 600 700
Clay content [g kg-1]
Results – MOM topsoil
80
r = 0.83 r = 0.55
p < 0.01 p < 0.05
60
MOM [g kg-1]
40
20
Hainich
Hesse
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 2 4 6 8 10 12 14 16 18
-1 -1
Alo [g kg ] Fed [g kg ]
Results – Mineralization rates subsoils
10-20 cm soil depth r = -0.40
0.25 p < 0.05
Mineralization rate [gCO2 g-1 C]
0.20
0.15
0.10
0.05
Hainich
Hesse
Soroe
0.00
0 100 200 300 400 500 600 700
-1
Clay [g kg ]
Results – Mineralization rates subsoils
20-30 cm soil depth r = -0.53
p < 0.01
Mineralization rate [g CO2 g soilC] 0.30
0.25
-1
0.20
0.15
0.10
0.05 Hainich
Hesse
Soroe
0.00
0 20 40 60 80 100
MOM [%]
Results – Mineralization rates subsoils
20-30 cm soil depth r = -0.70
p < 0.01
Mineralization rate [g CO2 g-1 soil C] 0.30
0.25
0.20
0.15
0.10
0.05
Hainich
Hesse
0.00
12 14 16 18 20 22 24 26 28 30
Sum pedogenic oxides [g kg-1]
Results – MOM subsoil
20-30 cm soil depth
r = 0.74
18 p < 0.01
16
14
12
MOM [g kg ]
-1
10
8
6
4
Hainich
2 Hesse
Soroe
0
0 20 40 60 80
Clay [g kg-1]
Results – MOM subsoil
10-20 cm soil depth r = 0.90
p < 0.01
30
25
20
MOM [g kg ]
-1
15
10
5
Hainich
Hesse
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
-1
Alo [gC kg ]
Results – Corg and soil properties
MOM Clay Alo Fed
[g kg-1]
Corg 0-5 cm 0.89** 0.42* 0.79** 0.44
Corg 5-10 cm 0.97** 0.37** 0.86** 0.51*
Corg 10-20cm 0.95** 0.25 0.84** 0.68**
Corg 20-30cm 0.90** 0.64** 0.53* 0.68**
*p < 0.05, **p < 0.01
Summary and Conclusions
• Large contributions of MOM to total C
→ lower mineralization rates especially in the topsoil
• Large clay contents in the soil
→ lower mineralization rates
• Total amount of MOM is related to the clay content
and the amount of pedogenic Fe and Al oxides
Summary and Conclusions
• Overall lowest mineralization rates in the old growth
forest Hainich with the highest content of
- clay
- MOM
- pedogenic oxides
This site also contains the oldest carbon
→ Role of clay + its composition in the protection
of OM needs further attention so that it can be
included in soil models
Thank you!
We would like to thank the EU for financing CarboEurope
IP Contract No. GOCE-CT2003-505572
Many thanks to:
- Marco Pöhlmann, Dunja Grüsser, Alexander Sinz,
Antje Brückner and Thomas Heinze for
their help with field work
- Ulrike Maul for doing the particle-size analyses
- The chemical analytical department
(especially Ines Hilke)
Results – Δ14C of MOM
Delta 14C
-300 -200 -100 0 100 200
0
10
Soil depth [cm]
20
30
Hainich
Hesse
Soroe
40
Results – Mineralization rate
10-20 cm soil depth
r = 0.758
5 p < 0.01
4
Ald [g kg-1]
3
2
1
0
5 10 15 20 25 30
-1
MOM [gC kg ]
