Transcript Soil Carbon in Greenbelt Park

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
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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?
Sample Location
Sample Location
Sample Location
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
Part I. Soil Characteristics
• Percent Water
%H 2 O  100% 
Mass wet  Mass dry
Volumewet
• Bulk Density
Dry Bulk Density 
Mass dry
Volumewet
• Porosity
 Dry Bulk Density
Porosity  100%  1 
2.65 g / cc




Water Content
Percent of Volume
0%
10%
0
Depth (cm)
10
30
20%
30%
40%
50%
60%
70%
80%
90%
100%
26.1
16.6
14.6
Water
Soil
50
70
90
15.5
33.5
35.3
Dry Bulk Density and Porosity
2
25
1.8
40
1.4
1.2
55
1
0.8
70
0.6
0.4
85
0.2
0
0
20
40
60
Soil Depth (cm)
80
100
100
Porosity (%)
Dry Bulk Density (g/cc)
1.6
Carbon Ratio
5.00
4.50
4.00
Percent Carbon
3.50
3.00
2.50
2.00
1.50
1.00
0.50
0.00
0
20
40
60
Soil Depth (cm)
80
100
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
Dry Massi (kg) x Carboni (%) = Mass Ci (kg)
} dz = 1 mm
Mass carbon
(kg per m2 of land, 1 m deep)
1000
Mass C   Mass Ci
i 1
etc.
x=1m
z=1m
1.2
1.0
0.8
mass.kg
1.4
1.6
Profile Mass
0.0
0.2
0.4
depth.m
0.6
0.8
2
1
carbon.pct
3
4
Percent Carbon
0.0
0.2
0.4
depth.m
0.6
0.8
Total Soil Carbon Storage
• Carbon per m2 of land, 1 m deep:
1.15 kg
• Area of Greenbelt Park
4.76 x 106 m2
• Mass of Soil Carbon
~5500 tonnes
~about 25% of a day’s driving in Maryland
Part III. Evidence of Past
Agriculture
Profile Mass
1.0
1.2
mass.kg
1.4
1.6
• Soil Density
(30 cm > 50 cm < 70 cm)
0.8
• Soil Porosity
(30 cm < 50 cm > 70 cm)
0.0
0.2
0.4
0.6
0.8
depth.m
2
1
carbon.pct
• Soil Carbon Content
(30 cm < 50 cm > 70 cm)
3
4
Percent Carbon
0.0
0.2
0.4
depth.m
0.6
0.8
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.
Part III. Evidence of Past
Agriculture
• 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 d13Cref + 1) x 0.011237
Carbon Ratio
0.01095
0.01095
0.01094
13C/12C
0.01094
0.01093
0.01093
0.01092
0.01092
0.01091
0
20
40
60
Soil Depth (cm)
80
100
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
References
DeFries, 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