Soil Carbon in Greenbelt Park Jay S. Gregg May 10, 2006.

Soil Carbon in Greenbelt Park

Jay S. Gregg

May 10, 2006

Background

• The largest terrestrial carbon pool is in the soil, 1.5 to 2.5 times that of vegetation (Wang et al., 2002)

• This is one of the areas with the most uncertainty within the global carbon cycle (Wang et al., 2004).

• Land use and land cover change affects soil carbon storage (DeFries et al., 1999).

History

• prior to 1700s: forests of oak, walnut, poplar, and elm • mid 1700s: first settlers, deforestation began• 1742: Bladensburg founded, navigable waterways• 1750s-1850s: land cleared, converted to tobacco

agriculture• 1850s-1900s: soil degradation lead to more corn and

vegetable crops• 1900s: farms abandoned• 1910s: dense thicket• 1920s: trees dominate• 1935-1938: Greenbelt, MD built under New Deal, area

scheduled to be converted to housing• 1947: Land acquired by state for B-W Parkway• 1950: National Park Designation

10 years after abandonment

20 years after abandonment

Questions

• What is the approximate soil carbon storage of Greenbelt Park?

• Is there evidence of past agricultural activities in the 13C/12C record?

Sam

ple

Loca

tion

Sam

ple

Loca

tion

Sam

ple

Loca

tion

Methodology

• 80 ml of wet soil collected at surface, 10cm, 30cm, 50cm, 70cm, 90cm depths

• Samples weighed, dried, reweighed

• Samples ground, and analyzed for carbon content

• Percent Water

• Bulk Density

• Porosity

Part I. Soil Characteristics

wet

dry

Volume

MassDensityBulkDry

wet

drywet

Volume

MassMass %100OH% 2

ccg /65.2

DensityBulk Dry 1%100Porosity

Water Content

26.1

16.6

14.6

15.5

33.5

35.3

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0

10

30

50

70

90

De

pth

(c

m)

Percent of Volume

Water

Soil

Dry Bulk Density and Porosity

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0 20 40 60 80 100

Soil Depth (cm)

Dry

Bu

lk D

en

sit

y (

g/c

c)

25

40

55

70

85

100

Po

ros

ity

(%

)

Carbon Ratio

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 20 40 60 80 100

Soil Depth (cm)

Pe

rce

nt

Ca

rbo

n

Part II. Carbon Content

• Standard method:

Cd= H x B x O

Cd = Carbon Density

H = Thickness of soil layer

B = Bulk Density

O = Organic Carbon Content (Wang et al., 2004)

Part II. Carbon Content

} dz = 1 mm

z = 1 mx = 1 m

y =

1 m

Dry Massi (kg) x Carboni (%) = Mass Ci (kg)

etc.

Mass carbon (kg per m2 of land, 1 m deep)

1000

1iiCMassCMass

0.0 0.2 0.4 0.6 0.8

0.8

1.0

1.2

1.4

1.6

Profile Mass

depth.m

ma

ss.k

g

0.0 0.2 0.4 0.6 0.8

12

34

Percent Carbon

depth.m

carb

on

.pct

Total Soil Carbon Storage

• Carbon per m2 of land, 1 m deep:1.15 kg

• Area of Greenbelt Park4.76 x 106 m2

• Mass of Soil Carbon~5500 tonnes

~about 25% of a day’s driving in Maryland

Part III. Evidence of Past Agriculture

• Soil Density (30 cm > 50 cm < 70 cm)

• Soil Porosity (30 cm < 50 cm > 70 cm)

• Soil Carbon Content (30 cm < 50 cm > 70 cm)

0.0 0.2 0.4 0.6 0.8

0.8

1.0

1.2

1.4

1.6

Profile Mass

depth.m

ma

ss.k

g

0.0 0.2 0.4 0.6 0.8

12

34

Percent Carbon

depth.m

carb

on

.pct

Part III. Evidence of Past Agriculture

• 13C/12C ratio?

• Because it’s lighter, 12C is reacts more readily than 13C in biological processes.

• Organic matter becomes 12C enriched relative to the inorganic carbon pool from which it has been taken.

• Soils high in organic matter should have a lower 13C/12C ratio.

• Determining the ratio:– Raw data in given as per mil difference from

PDB (Pee Dee Belemnite)

13C/12C PDB ratio = 0.011237

Sample 13C/12C =(0.001 x 13Cref + 1) x 0.011237

Part III. Evidence of Past Agriculture

Carbon Ratio

0.01091

0.01092

0.01092

0.01093

0.01093

0.01094

0.01094

0.01095

0.01095

0 20 40 60 80 100

Soil Depth (cm)

13

C/1

2C

Conclusions

• A profile sample allows an approximation of soil carbon storage for the park

• The data is consistent with past agricultural practices– HOWEVER,

Because of cost, the sample size is small. More profiles should be taken and analyzed to better understand spatial variations and to minimize uncertainties

ReferencesDeFries, R. S., Field, C. B., Fung, I., Collatz, G. J., & Bounoua, L. (1999).

Combining satellite data and biogeochemical models to estimate global effects of human-induced land cover change on carbon emissions and primary productivity. Global Biogeochemical Cycles, 13(3), 803-815.

Wang, S., Huang, M., Shao, X., Mickler, R. A., Li, K., & Ji, J. (2004). Vertical Distribution of Soil Organic Carbon in China. Environmental Management, 33(Supplement 1), S200-S209.

Wang, S., Tian, H., Liu, J., & Pan, S. (2003). Pattern and change of soil organic carbon storage in China: 1960s-1980s. Tellus, 55B, 416-427.

Wang, S., Xu, J., Zhou, C., & He, C. (2002). Using remote sensing to estimate the change of carbon storage: a case study in the estuary of the Yellow River delta. International Journal of Remote Sensing, 23(8), 1565-1580.

Acknowledgements

• Dr. Alan Jay Kaufman

• Chrissy France

• Nick Collins