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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