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

-200

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plan

d m

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Seta

side,

LU

C &

agro

fore

stry

Gra

zing

land

man

agem

ent

Res

tore

cul

tivat

edor

gani

c so

ils

Res

tore

deg

rade

dla

nds

Bio

ener

gy (s

oils

com

pone

nt)

Live

stock

Man

ure

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

0

0.5

1

1.5

2

2.5

Ao Fr Lp Am Pl Rr Lc Tp Tr

Tota

l fun

gal P

LFA

(nm

ol g

dry

soi

l-1)

0

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Ao Fr Lp Am Pl Rr Lc Tp Tr

F:B

PLFA

Individual plant species effects on soil microbial abundance, activity and community structure

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C (m

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-1)

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Ao Fr Lp Am Pl Rr Lc Tp Tr

Mic

robi

al re

spira

tion

(μl C

O2 g

-1h-1

evo

lved

)

a

ab ab ab

b b

b b

b b

b b

b b b

a

b b

a

ab ab

ab

ab

b ab

b b

b b b

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 )

0

20

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60

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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)

36

12

12

64482424Total/soil fertility (4blocks)G+F+L (Lp+Ao+Pl+Am+Tr+Lc)

---

-----

---

0

4

0 ----1 4

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)

36

12

12

64482424Total/soil fertility (4blocks)G+F+L (Lp+Ao+Pl+Am+Tr+Lc)

---

-----

---

0

4

0 ----1 4

De Deyn et al. (2009) Journal of Ecology, 97, 864-875

Does plant species diversity promote carbon sequestration?

a

a ab

b

a

b

a

c

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1 2 3 6 Species richness

Tota

l roo

t C (g

.m-2

)

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.

a

a ab

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a

b

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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

b

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

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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

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c ex

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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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0.56

No seed T. pratense Seed treatment 2004

Tota

l soi

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g.m

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Seed treatment 2004

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Seed treatment 2004

T. p

rate

nce

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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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no T. pratensewith T. pratense

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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)

Net

pho

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(% o

f co

ntro

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[CO2] (μmol mol-1 added to ambient)

To

tal

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ma

ss(%

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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: journals.permissions@oup.com

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