Geologic Control of Soil Carbon Sequestration – Examples from Western Conifer Forests Craig...
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Transcript of Geologic Control of Soil Carbon Sequestration – Examples from Western Conifer Forests Craig...
Geologic Control of Soil Carbon Geologic Control of Soil Carbon Sequestration – Sequestration –
Examples from Western Conifer ForestsExamples from Western Conifer Forests
Craig RasmussenCraig RasmussenDept. of Soil, Water and Environmental ScienceDept. of Soil, Water and Environmental Science
The University of ArizonaThe University of Arizona
Global Carbon Cycle – why do we care?
Figure TS.6
Image from the Climate and Vegetation Research Group, Boston University
Global Carbon Cycle
Pool size and fluxAtmospheric CO2 sinks:
land-atmosphere; ocean-atmosphere
Soil carbon – largest terrestrial pool
Source/sink dynamic
Terrestrial Carbon Stocks
Ecosystem Type Soil Carbon Litter Carbon Total Carbon % of Total
Tropical Forest 255 3.6 259 17Temperate Forest 142 14.5 157 10Boreal Forest 179 24.0 203 13Woodland and Shrubland 59 2.4 61 4Tropical Savanna 56 1.5 58 4Temperate Grassland 173 1.8 175 12Tundra and Alpine 173 4.0 177 12Desert Scrub 101 0.2 101 7Extreme 3 0.0 3 0Cultivated 178 0.7 179 12Swamp and Marsh 137 2.5 140 9Total 1456 55 1511From Schlesinger (1992)
mt C x 109
Forests 40% of Global SOC
Forests ~1/3 of US carbon
North America Carbon Stocks
Forests – east and west
West predominantly conifer forests
Source: Climate Change Science Program
Forests ~1/2 of US terrestrial C sink
Western Conifer Forests
• Complex physiography– Geology– Climate– Ecosystems
• California and Arizona
Bedrock Geology
MAT (Cx100)
Value
High : 2549
Low : -420
MAP (mmx100)
Value
High : 710807
Low : 4759
Winter PPT (% of MAP)
Value
High : 96
Low : 15
WinterWinter
XericXeric
SummerSummer
UsticUstic
Desert
Forest
Agricultu
re
Savanna
Chaparral
Grassland
Other
Rel
ativ
e P
erce
nt
0
10
20
30
40
50
% Land Area % of Total SOC
Forest
Upper Dese
rt
Lower Dese
rt
Shrub-grass
Grassland
Rel
ativ
e P
erce
nt
0
10
20
30
40
% Land Area% Total SOC
Data derived from GAP and STATSGO – 4-km pixel resolution
California
ArizonaForests – disproportionate SOC relative to land area
Clay content not a good predictor of SOC in these systems
California Conifer EcosystemsCalifornia Conifer Ecosystems
Significant difference in SOC content among geologic parent materials
Parent Parent MaterialMaterial
SOC SOC
(kg m(kg m-2-2))
AndesiteAndesite 8.7 A8.7 A
BasaltBasalt 8.1 B8.1 B
GraniteGranite 5.9 C5.9 C
How does geology control SOC sequestration?
• Metal and mineral interactions– Organo-metal complexation– Mineral adsorption
• Microbial community composition– Diversity and function
• Aggregation– Mineral-mineral and organo-mineral– Occlusion and physical protection
• All are highly dependent on soil mineral assemblage and should vary predictably with geologic parent material
Geology and Soil Carbon Studies
• Case studies– Sierra Nevada Conifer Forests
• Parent material and elevation gradients
– Arizona Ponderosa Pine Forests • Soil pH and Al gradient
• Empirical and Mechanistic data– Soil C mineralization– Microbial community composition– Aggregate stability and occlusion
Study 1: Sierra Nevada ForestsStudy 1: Sierra Nevada Forests
• Three elevation gradients on three igneous parent materials:– Granite (GR), Andesite (AN),
Basalt (BS)
• Three conifer ecosystems:– Pinus ponderosa (pp), Abies
concolor (wf), A. magnifica (rf)
• Very different mineral assemblages
100 0 10050 Kilometers
GG G G
GGGG
GGGG
Granite -------
Basalt -------
Andesite -------
Rasmussen et al. (2006) Global Change Biology.Rasmussen et al. (2007a, b) Soil Sci. Soc. Am. J.Rasmussen et al. (2008) Global Change Biology.Rasmussen et al. (In Press) Geoderma.
Red Fir, MAST 0-8ºC, Entisols
White Fir, MAST 8-10ºC, Inceptisols/Andisols
Ponderosa Pine, MAST 10-15ºC, Alfisols/Ultisols
2
4
6
8
10
12
14
Grassland
Savanna
Ponderosa Pine
White Fir
Red Fir
Alpine
Elevation (1000ft)
Alp (g kg-1)
0 2 4 6 8 10 12
Min
eral
ized
C (
mg
C g
-1 s
oil C
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Soil C Mineralization
Pooled by Parent Material
0
2
4
6
8
10
12
14
16
GR BS AN
[mg
C (
g s
oil
C)-
1]
a
b
c
Pooled by Parent Material
0
2
4
6
8
10
12
14
16
GR BS AN
[mg
C (
g s
oil
C)-
1]
a
b
c
Study 2: Arizona Forests• Arizona Ponderosa Pine Forests
– Al effects on microbial community structure and soil C sequestration
– Lithosequence of four parent materials• pH gradient and variable soil mineral assemblage
Heckman et al. (2009) Chemical Geology.
Limestone Basalt Granite Rhyolite
High pH (7.0) Low pH (5.0)
Low available Al High available Al
Significant correlation between soil C and metal-organic complexes
Significant variation in soil C mineralization by parent material
Alp (kg m-2)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8
soil
orga
nic
carb
on
(kg
m-2
)
0
2
4
6
8
10
12
14
LimestoneRhyoliteGraniteBasaltR2 = 0.72, P<0.0001
Incubation Day
0 10 20 30 40
mg
C r
espi
red
(g s
oil C
)-1
0
20
40
60
80
100
120
LimestoneBasaltGraniteRhyolite
Microbial Community Composition
Significant variation by parent material
Correlated with:• pH• exchangeable Al• metal-organic complexes• SRO Fe-oxides
• Soil pH, diversity and Al-tolerant microbes
Microbial Community Composition
R2 = 0.5344
2
2.5
3
3.5
4
0.1 10 1000 100000
KCl extractable Al (ng/g dry soil)
Div
ersi
ty
Welty-Benard, et al. In preparation.
Study 3: Physical Mechanisms
Free Light Fraction (FLF) Occluded (OCC)
Mineral (MIN)
Physical Mechanisms - Aggregation
FLF OCC MIN
14C
-400
-300
-200
-100
0
100
200
RhyoliteGraniteBasaltLimestone
0%
20%
40%
60%
80%
100%
Rhyolite Granite Basalt Limestone
MINOCLFLF
“Young”
“Old”
Overall Summary:• Geology and soil mineralogy matter
– Non-crystalline mineral species and metal-organic complexation
• Mineral control of soil C recalcitrance– Microbial community activity and composition– Chemical and physical protection mechanisms
• Within a given ecosystem soil carbon sequestration varies predictably with geology
FLF OCC MIN
14C
-400
-300
-200
-100
0
100
200
RhyoliteGraniteBasaltLimestone
Alp (g kg-1)
0 2 4 6 8 10 12
Min
eral
ize
d C
(m
g C
g-1
so
il C
)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
Acknowledgements:
• Students– Katherine Heckman, Amy Welty-Benard, Jessica
Hagerlin-Jones, Angelica Vazquez-Ortega, Mateo Cagnasso
• NSF DEB#0543130