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Harnessing plant-soil interactions for the enhancement of carbon sequestration in soil Richard Bardgett, Gerlinde De Deyn, Kate Orwin, Dario Fornara, Sue Ward,, Franciska De Vries,Catherine Turner, Helen Quirk, Simon Oakley & Nick Ostle
6.5 1-2
Annual increase 3 Gt
Land sink 1-3
Ocean sink about 2
6.5 1-2
Atmosphere: +3
Global Carbon Budget (Billions tonnes C y-1; Royal Society, 2001)
Vegetation: 500 Pg C Soil OC: 1500 Pg C
Rate change in atmospheric C02 = Emissions - Land sink – Ocean sink
Biota 560 Gt
Atmosphere 760 Gt
+3.3 Gt/yr
Soils 2,500 Gt
(i) SOC - 1,550 Gt (ii) SIC - 950 Gt
Ocean 38,400 Gt + 2.3 Gt/yr
(i) Surface layer: 670 Gt (ii) Deep layer: 36,730 Gt (iii) Total organic: 1,000 Gt
Fossil Fuels 4,130 Gt
(i) Coal: 3,510 Gt (ii) Oil: 230 Gt (iii) Gas: 140 Gt (iv) Other: 250 Gt
120 + 2.0 Gt/yr (photosynthesis) Plant respiration
60 + 1.6 Gt/yr
60 Gt/yr
6.3 Gt/yr Fossil fuel combustion
90 Gt/yr
0.6+0.2 Gt/yr (deposition)
MRT = 5Yr
MRT = 25Yr
Mean Residence Time (MRT) = 400Yr
1.6 + 0.8 Gt/yr Deforestation
MRT = 6Yr
92.3 Gt/yr
Biofuel offset?
Soil is the third largest global C pool (2500 Pg C)
Lal (2008)
Management of grassland for carbon
Grasslands cover approx 50% UK land surface and contain 32% of the UK soil C store (Countryside survey 2007)
Grassland soil C (surface and sub-surface) sensitive to management
Ward et al. (in preparation): National survey of 180 grassland sites in England
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Cro
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d m
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Seta
side,
LU
C &
agro
fore
stry
Gra
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land
man
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Res
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tivat
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gani
c so
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Res
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deg
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dla
nds
Bio
ener
gy (s
oils
com
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nt)
Live
stock
Man
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man
agem
ent
Mitigation measure
Glo
bal b
ioph
ysic
al m
itiga
tion
pote
ntia
l (M
t CO 2-e
q. y
r-1)
N2OCH4CO2
Smith et al. (2008)
Climate change mitigation potential farming systems
plant-soil-Micorbial interactions and carbon dynamics
(1) Plant-soil-microbial interactions and carbon cycling at the individual plant level
(2) Manipulating plant diversity for soil carbon in grassland
(3) Impacts of climate change
Courtesy of Michael Bahn, University of Innsbruck
Part 1. Plant-soil-microbial interactions and carbon dynamics
Landscape-scale soil C content of UK grassland primarily determined by abiotic factors
Manning, De Vries, Bardgett & the DIGFOR team (in preparation)
De Deyn et al (2008) Ecology Letters
Various forms & age
CO2
Litter
Soil
Organic carbon
Shoots
Roots
Soil biota
Exudates
Respiration
Photosynthesis
C-in C-out
Leaching
Local-scale: Plant-soil-microbial interactions and carbon dynamics
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Ao Fr Lp Am Pl Rr Lc Tp Tr
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l fun
gal P
LFA
(nm
ol g
dry
soi
l-1)
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F:B
PLFA
Individual plant species effects on soil microbial abundance, activity and community structure
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g C
dry
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-1)
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(μl C
O2 g
-1h-1
evo
lved
)
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ab ab ab
b b
b b
b b
b b
b b b
a
b b
a
ab ab
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b ab ab
ab ab
a
F = 3.79, P = 0.0006 F = 5.67, P <0.0001
F = 3.46, P = 0.0013 F = 3.53, P = 0.0011
A. B.
C. D.
Harrison and Bardgett (2010) Journal of Ecology
Soil biological properties related to plant traits – across 9 species
Orwin et al. (2010) Journal of Ecology, 98, 1074-1083.
Soil C stock (~ 10%)
Plant trait based framework for promoting soil carbon sequestration
De Deyn, Cornelissen & Bardgett. 2008 Ecology Letters 11, 516-531.
Rapid transfer of plant-derived photosynthetic C to soil microbes: inter-species variation in transfer C to soil and microbial communities variation
De Deyn et al. (2011) Biogeosciences, 8, 1131-1139.
Species
DG AO LP BM
13C
mas
s (µ
g 13
C )
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13C in microbial biomass13C respired by microbial biomass duri
[+N]
Consequences for soil carbon sequestration and loss, and N dynamics, poorly understood.
Increased plant diversity
Plant resource use
complementarity (+)
Positive interactions
(+)
Root exudates
diversity (+)
Plant litter diversity (+)
Net primary productivity
(+)
Plant nutrient
uptake (+)
Detrital and root exudate quantity (+)
Decomposer diversity (+)
Decomposer resource use
complimentarity (+)
Microbial biomass and soil fauna (0,+)
Microbial biomass and soil fauna (-)
Long-term accumulation of organic matter (-, 0,+)
Short-term decomposition and nutrient mineralization
(-, 0,+)
Nutrient supply to plants (-, 0, +)
Part 2: Does plant diversity matter for soil C dynamics? Hypothetical mechanisms by which changes in plant diversity might effect
soil biological properties and soil organic matter dynamics
Litter inputs
Root inputs
G+F (e.g. Lp+Am)
--1-G+G (Lp+Ao)
--1-L+L (Tr+Lc)
--1-F+F (Pl+Am)
1---2--G+F+L (e.g. Lp+Pl+Tr, Ao+Am+Lc)3
--1-F+L (e.g. Pl+Tr)
--1-G+L (e.g. Ao+Lc)
--1-2
---2F (Pl, Am)
---2L (Tr, Lc)
---2G (Lp, Ao)1
6321Functional Group richness (composition)
Species richness Total/soil fertility (4blocks)
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12
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64482424Total/soil fertility (4blocks)G+F+L (Lp+Ao+Pl+Am+Tr+Lc)
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G+F (e.g. Lp+Am)
--1-G+G (Lp+Ao)
--1-L+L (Tr+Lc)
--1-F+F (Pl+Am)
1---2--G+F+L (e.g. Lp+Pl+Tr, Ao+Am+Lc)3
--1-F+L (e.g. Pl+Tr)
--1-G+L (e.g. Ao+Lc)
--1-2
---2F (Pl, Am)
---2L (Tr, Lc)
---2G (Lp, Ao)1
6321Functional Group richness (composition)
Species richness Total/soil fertility (4blocks)
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64482424Total/soil fertility (4blocks)G+F+L (Lp+Ao+Pl+Am+Tr+Lc)
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De Deyn et al. (2009) Journal of Ecology, 97, 864-875
Does plant species diversity promote carbon sequestration?
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1 2 3 6 Species richness
Tota
l roo
t C (g
.m-2
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Root C content
Grassland plant species and functional group diversity (legumes) enhance root C and AM fungi, and hence C allocation belowground
De Deyn et al. (2009) J Ecol 97, 864-875.
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1 2 3 6 Species richness
Tota
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.m-2
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Root C content
Grassland plant species and functional group diversity (legumes) enhance root C and AM fungi, and hence C allocation belowground
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Plant species richnessA
MF
(ug/
g)
F4,114= 2.73 P< 0.05
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ab ab a a
AM fungal biomass (16:1ω5)
De Deyn et al. (2011) Biology Letters, 7, 75-78. De Deyn et al. (2009) J Ecol 97, 864-875.
GG FF LL GF GL FL
Soil Carbon Content after 2 years (%)
Fornara and Tilman (2008) J. Ecol. 96: 314-322
Soil C accumulation related to root biomass
Soil Carbon Content
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Feb March April May June N
et C
O2-
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xcha
nge
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(g C
.m-2
h-1 )
1 6 species
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B
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6 species Lc Tr Am Pl Ao Lp Net
eco
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em C
O2-
c ex
chan
ge ra
te (g
C.m
-2.h
-1)
a a a
ab
ab
b b
Influence of species diversity and identity of net CO2 exchange
Potential to manage plant diversity for soil C storage?
Total soil carbon storage: benefits of legumes in long-term biodiversity restoration experiment
Soil C stock (~ 10%)
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No seed T. pratense Seed treatment 2004
Tota
l soi
l N (k
g.m
-2) **
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Seed treatment 2004
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g.m
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Seed treatment 2004
T. p
rate
nce
abun
danc
e
(% c
over
)
Cover Trifolium Soil N stock (~ 10%)
De Deyn et al. (2011) Additional benefits for carbon sequestration of grassland biodiversity restoration. Journal of Applied Ecology 48, 600-608
Time
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Gro
ss C
O2-
C e
xcha
nge
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(g C
O2-
C m
-2h-
1 )
no T. pratensewith T. pratense
Time
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Gro
ss C
O2-
C e
xcha
nge
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(g C
O2-
C m
-2h-
1 )
no T. pratensewith T. pratenseno T. pratense
with T. pratense
Reduced C loss through respiration
De Deyn et al. (2011) Potential to manage plant diversity for soil C storage?
SOIL ORGANIC MATTER
Litter Rhizodeposits
Microbial biomass Soil fauna
Net Primary Production
Direct feedback Temperature
Extreme events
Indirect feedback Elevated CO2
Temperature/precipitation CO2
Nutrient cycle feedback
Heterotrophic respiration
Autotrophic respiration
CLIMATE CHANGE
DOC
3. Impacts of climate change
Bardgett et al. (2008) The ISME Journal, 2, 805-814.
Elevated atmospheric CO2
Plant production Plant community composition
+ when nutrient replete
Quantity/quality C inputs to soil
Soil biota (microbes and their predators
Soil C storage
Soil C mineralization
CO2
Schematic of indirect responses to elevated CO2
+ root derived carbon
• 6 tree species • 4 CO2 concentrations • 2 levels of soil nutrients • grown in 12 Solardomes for 2 years
• Konza Prairie, Kansas(12 tons!) • Dominated by C4 grasses • δ13C of soil: -14.7‰ • δ13C of (C3) tree roots: -27‰ (ambient air) -40‰ (ambient +300ppm CO2)
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[CO2 ] (μmol mol-1 added to ambient)
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pho
tosy
nthe
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ate
(% o
f co
ntro
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[CO2] (μmol mol-1 added to ambient)
To
tal
bio
ma
ss(%
of
con
tro
l) no added nutrients, added nutrients
Net photosynthesis (mean 6 species expressed as % control)
5-month, 10-month and 15-month harvests, no added nutrients; 15-month harvest, added nutrients.
Total tree biomass (mean 6 species
expressed as % control)
Conclusions
1. Soil carbon dynamics influenced by range of global change factors, including land use, climate change and nutrient enrichment
Challenge: Determine the relative and interactive effects of global change drivers on plant-soil interactions and C dynamics
2. Plant-soil-microbial interactions major drivers of ecosystem C dynamics via a variety of mechanisms, but much to be learned
Challenge: Relative importance of different routes by which changes in plant communities influence soil communities and C dynamics, especially role recent photoassimilate C (priming effect)
3. Potential to manage plant composition/diversity for soil C sequestration, and opportunities for crop improvement based on root traits (deeper and broader roots)
Challenge: How plant traits (especially roots) select for soil biotic communities and consequences for C dynamics in agricultural systems under climate change
Potential for the improvement of agricultural and ecological traits by breeding crop plants with large root systems.
Kell, 2011. Ann Bot, 108:407-418 © The Author 2011. Published by Oxford University Press on behalf of the Annals of Botany
Company. All rights reserved. For Permissions, please email: [email protected]
1. Potential to increase soil C?
2. But, also potential to cause C loss via priming effects on old C?
3. Research effort required to realize the potential for crop improvement based on root traits that favour carbon sequestration whilst also producing food