Contrasting effects of increased carbon
input on boreal SOM decomposition with
and without presence of living root
system of Pinus sylvestris L.
Lindén A.1, Heinonsalo J.1, Buchmann N.2, Oinonen M.3, Sonninen E.3, Hilasvuori E.3, Pumpanen J.1
1University
2ETH
3University
of Helsinki, Department of Forest Sciences, Finland
Zurich, Institute of Agricultural Sciences, Switzerland
of Helsinki, Finnish Museum of Natural History, Laboratory of Chronology, Finland
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1
Scientific understanding of climate feedback
effects (Arneth et al. 2010 Nature Geoscience)
The understanding on the feedback mechanisms between C and N cycle and CO2
fertilization is low or very low.
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2
Ecosystem C and N pool and flux measurements
Hyytiälä Southern Finland
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3
Long-term measurements of the carbon balance of
a boreal Scots pine dominated forest ecosystem.
Ilvesniemi H. et al. 2009. Long-term measurements of the carbon balance of
a boreal Scots pine dominated forest ecosystem. Boreal Environment
Research 14: 731–753.
Canopy
photosynthesis
1100 g C m-2
Canopy respiration
300 g C m-2
Photosynthesis of
ground vegetation
100 g C m-2
Annual tree growth
200 g C m-2
Carbon stock in trees
4500 g C m-2
Soil CO2 efflux 600-700 g C m-2
Stem respiration
100 g C m-2
Respiration of
ground vegetation
50 g C m-2
Root and rhizosphere
respiration
Decomposition of soil
organic matter
~300 g C m-2
~300 g C m-2
Litter production
100 g C m-2
?
Lateral transport
10 g C m-2
Soil carbon stock~ 7000 g C m-2
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Nitrogen balance in a 50 year-old P. sylvestris stand. Korhonen
et al. 2013. Biogeosciences 10: 1083-1095
— 30% of nitrogen
used for plant
growth was from
deposition
— Nitrogen uptake
and retranslocation were of the
same importance
as sources of N for
plant growth
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OBJECTIVES
— To quantify the
contribution of root and
rhizosphere in the C
balance of boreal trees
— To understand the effect
of increased energy input
into the soil on the
decomposition of old
recalcitrant soil organic
matter
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Process level studies in laboratory
Below ground C allocation 14C pulse labelling
Pumpanen et al. 2009 (Trees-Structure and Function), Heinonsalo et al. 2010 Soil Biology & Biochemistry)
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14C
was
8.00
§
14C
9-30% of the assimilated
was
found in root and rhizosphere
respiration
Scots pine % of the assimilated 14CO2
Silver birch % of the assimilated 14CO2
Norway spruce% of the assimilated 14CO2
7.00
14
25-65% of the assimilated
allocated above ground
%of assimilated C
§
6.00
5.00
4.00
3.00
2.00
1.00
§
0.00
Pulse emerged from the root
system after 1-2 days following
the labeling
0
2
4
6
8
§
Some root-associated mycorrhiza
alter plant CO2 exchange, biomass
distribution, and the allocation of
recently photosynthesized carbon.
Allocation of assimilated 14C (%)
Fastest pulse with Silver birch and
slowest with Norway spruce
12
70
Silver birch
60
§
10
Days since labelling
Norway spruce
Scots pine average
50
40
30
20
10
0
Leaves
Stem
Root and
mycorrhizal
biomass
Soil
Root and
rhizosphere
respiration
Pumpanen J., Heinonsalo J., Rasilo T., Hurme Kaj-Roger
and Ilvesniemi H. 2009. Trees-Structure and Function
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INCUBATION EXPERIMENT
Contrasting effects of increased carbon input on boreal SOM decomposition with
an without presence of living root system of P. Sylvestris. Lindén A., Heinonsalo J.,
Buchmann N., Oinonen M., Sonninen E., Hilasvuori E. and Pumpanen J. 2014. Plant and Soil
377 (1-2): 145-158.
Treatment 1
SOM only
— C4-glucose treatment
during 1 month +
incubation afterwards
Treatment 2
SOM + glucose
— Natural abundance of
isotopes 14C, 13C, 15N
Treatment 3
SOM + Seedling
— Enzyme activity
(protease)
— Photosynthesis (Pmax)
Treatment 4
SOM + seedling +
glucose
— Nutrient contents ICP, C/N
— Soil fauna nematodes, bacteria,
mycorrhiza
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14C
dating
Radiocarbon content in the atmosphere as fraction modern FM
2,2
Levin I and Kromer B. 2004. Radiocarbon 46:pp.1261-1272
14C
Nuclear tests in the
atmosphere increased
1,8
Fraction modern
dating of the
respiration with
molecular sieve
sampling of the soil
CO2 efflux before and
after incubation.
2,0
14C
1,6
1,4
1,2
1,0
1950
1960
1970
1980
1990
2000
2010
Calendar year
CO2 was analysed with
AMS (Accelerator Mass
Spectrometry)
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RESULTS
Presence of seedlings
resulted in older C in
respired CO2 ->
smaller pMC-value
Age of C in respired CO2
SOM
SOM+
glucose
SOM+
seedling
SOM+
glucose+
seedling
More decomposition
of older SOM
Glucose addition as
such did not seem to
affect the pMC-value
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RESULTS
SOM
SOM+
SOM+
glucose seedling
SOM+
seedling+
glucose
SOM
SOM+
SOM+
SOM+
glucose seedling seedling+
glucose
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RESULTS
Ectomycorrhiza/root
biomass-ratio 100% higher
in glucose seedlings
compared to seedlings
without glucose.
More ectomycorrhizal
enzyme activity -> more
decomposition of old SOM
pool?
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RESULTS
Glucose induced a small
non-sinificant enrichment
of 15N in needles
Suggests increased
mineralization of N from
old SOM pool in glucose
treatments?
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SUMMARY
— Tree seedlings allocated about 50% of the
assimilated C to below ground root system (9-30%
in root and rhizosphere respiration)
— The age of C in soil CO2 efflux can be doubled in
the presence of living root system even if the
recently assimilated C consists of modern carbon
— Increase in energy input increases protease
activity and mineralization of nitrogen bound in
soil organic matter.
— Plants-soil interaction should be taken into
consideration in soil decomposition models.
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SUMMARY
— Easily available carbon can increase symbiotic N
acquisition from older soil organic matter.
— Higher mycorrhizal / root ratio
— Trend of d15N enrichment in needles after
glucose treatment
— Decomposition of SOM is strongly linked to
priming, plant N uptake and rhizomicrobiology
— SOM incubation studies without the presencence
of living root system may give highly different
results on SOM decomposition compared to the
situation where living root system is present
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THANK YOU FOR YOUR ATTENTION!
Acknowledgments:
Academy of Finland project 2180984 and
Academy of Finland Centre of Excellence Program
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