Determining Amounts of Carbon Loss and

Changes in 13C Values From Soils Due To Biomass Burning

Scott Werts

Hope JahrenDepartment of Earth and

Planetary Sciences

Johns Hopkins University

0 2 4 6 8 10

Total Global Emissions(Pyne et al, 1996)

Global Anthropogenic Emissions

Global Fire Emissions

Indonesia Fires, 1997(Page et al, 2002)

Indonesia Soil, 1997

US Total Anthropogenic(DOE, 2001)

Global Annual C Emission Estimates

Carbon Emissions (Gt)

Carbon Emissions (Gt)

Radiative Heating in Soil Profiles

• Limited attention paid to Corg loss from soils during fires.– Discussions center around high organic soils

(Histosols).

• Most soils contain several times the amount of carbon as the vegetation growing above it.

• Any soil can be affected by radiative heating during a fire.

• We chose soils at end members of pedogenic development in common landscapes.

Common Temperatures in Soil Beneath Fire

• Ranges from a few ˚C to over 700˚C– 3 to 8˚C (Werts and Jahren, unpublished data)

– 700˚C in boreal ground fire (Ryan, 2002)

• Temperature increase highly dependent on moisture content of soil.

Field Temperature Data

• Record temperature of soil during fire– Every cm through 4

cm deep in soil

0

100

200

300

400

500

600

700

0 0.5 1 1.5 2

0-1 cm

1-2 cm2-3 cm3-4 cm

Tem

pe

ratu

re (

ÞC

)

Elapsed Time (hours)

Soil Depth

Camp Singewald Soil Temperatures Due To Fire

Camp Singewald

Alfisol (older soil)

8 12 16 20 24

Percent Clay

% Clay

0 50 100 150 200 250

Corg

Content

g Corg

/ kg soil

0

10

20

30

40

50

60-28 -27 -26 -25 -24 -23

13 Corg

De

pth

(cm

)

13Corg

(‰)

Camp Singewald Inceptisol (younger

soil)

8 12 16 20 24

Percent Clay

% Clay

0 50 100 150 200 250

Corg

Content

g Corg

/ kg soil

0

10

20

30

40

50

60-28 -27 -26 -25 -24 -23

13 Corg

De

pth

(cm

)

13Corg

(‰)

Laboratory experiments

• Each horizon incinerated in Isotemp Muffle Furnace for 6 hours at temperatures ranging from 150 to 500˚C– Each have different amounts of organic carbon

and clay content

• Pre and post-incineration carbon mass determined from elemental analyzer

• Pre and post-incineration 13C values determined from mass spectrometer

Higher Temperatures Increase Carbon Loss Ratio

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

Camp Singewald Alfisol Temperature vs Corg

Loss Ratio

Organic HorizonHorizon 1Horizon 2Horizon 3Horizon 4Horizon 5Horizon 6

Co

rg L

os

s R

ati

o (

g C

org

lo

st/

g C

org

ori

gin

al)

Temperatures (ÞC)

0

0.2

0.4

0.6

0.8

1

0 100 200 300 400 500 600

Camp Singewald Inceptisol Temperature vs Corg

Loss Ratio

Organic HorizonHorizon 1Horizon 2Horizon 3Horizon 4Horizon 5

Co

rg L

os

s R

ati

o (

g C

org

lo

st/

g C

org

ori

gin

al)

Temperatures (ÞC)

Combustion of Select Soil Components:

Compound Chemical Description Change in 13C value from bulk plant/soil (ä)

Combustion Temperature

(ûC) Cellulose (C6H12O6)x (chain of glucose) +1 to +3.5 (3,9,10) 310-370

(1,2,3,4,5,6,7) Lignin High molecular weight,

polyphenolic compound, C18H24O11

-1 to -3 (3,9) 360 to 400 (4,6,8)

Chitin Glucose Polymer C8H12NO5 -0.5 (11,12) 270 to 285 (9)

Citations: (1) Davies, 1983; (2) Dollimore, 1981; (3) Loader, 2003; (4) Ghetti, 1996; (5) Kaloustian, 2000; (6) Susott, 1980; (7) Czimczik, 2002; (10) Schimmelmann, 1986; (8) Fenner, 1981; (9) Kim, 1998; (9) Schweizer, 1999; (10) Rundgren, 2003; (11) Schimmelmann, 1986; (12) Schimmelmann and DeNiro, 1986;

Similar 13C Fractionation Patterns Among Soil Horizons

-2

-1

0

1

2

3

4

0 100 200 300 400 500 600

Camp Singewald Alfisol Temperature vs C org

Organic HorizonHorizon 1Horizon 2Horizon 3Horizon 4Horizon 5Horizon 6

C o

rg (

C b

urn

ed -

C u

nb

urn

ed )

Temperatures (ÞC)

-2

-1

0

1

2

3

4

0 100 200 300 400 500 600

Camp Singewald Inceptisol Temperature vs C org

Organic HorizonHorizon 1Horizon 2Horizon 3Horizon 4Horizon 5

C o

rg (

C b

urn

ed -

C u

nb

urn

ed )

Temperatures (ÞC)

-2

-1

0

1

2

3

4

0.01 0.1 1 10

C or

g (

C bu

rned

-

C

unbu

rned

)

Original Corg

Content (g)

0

0.2

0.4

0.6

0.8

1C

org L

oss

Ra

tio (

g C

org lo

st/g

Co

rg o

rig

ina

l)

6 8 10 12 14 16 18 20

Alfisol

Inceptisol

% Clay

Above 100˚C, Carbon and Clay Content Have NoEffect on CLR or 13C Values

Carbon Loss From Soils Depths Over Time

Conclusions: Organic Carbon Losses

• Organic carbon is lost from the soil at temperatures as low as 150˚C.

• All measurable organic carbon is lost by 500˚C.

• The highest losses occur between 250 and 400˚C. – All soil horizons behaved in a similar manner

regardless of original carbon or clay content.

Conclusions: 13C values

13C values increase in all horizons between 250 and 400˚ regardless of original carbon or clay content

13C values below 250˚ may depend on the level of decomposition of the organic matter.

Future Directions:

• Further defining dynamics of 13C changes due to increasing temperature.

• Apply experimental procedures to more soil types.

• Morphology changes of heated soils determined by SEM – Applications to paleosols