Significant Bomb 14 C Enrichment in Deep Soil: A Previously Unrecognized Decadal C Pool? W. Troy...
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Transcript of Significant Bomb 14 C Enrichment in Deep Soil: A Previously Unrecognized Decadal C Pool? W. Troy...
![Page 1: Significant Bomb 14 C Enrichment in Deep Soil: A Previously Unrecognized Decadal C Pool? W. Troy Baisden and Roger L Parfitt Landcare Research, Palmerston.](https://reader038.fdocuments.in/reader038/viewer/2022103022/56649cb65503460f9497b908/html5/thumbnails/1.jpg)
Significant Bomb 14C Enrichment in Deep Soil: A Previously Unrecognized Decadal C Pool?
W. Troy Baisden and Roger L Parfitt
Landcare Research, Palmerston North, New Zealand
Funded by NZ Foundation for Research Science and TechnologyMinistry of Agriculture and Forestry
US-NZ Climate Change Partnership through NZ Govt
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-400 -200 0 200
0
50
100
150
Dep
th (
cm)
∆14C (‰, pre-bomb atm.= 0)
% Modern Carbon (1950 atmosphere)
80 100 12060
1952
1997
California Grassland Soil
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Baisden et al 2002, Global Biogeochemical Cycles
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Koputaroa, New ZealandGoh et al, 1976Syers et al, 1970
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Judgeford, New ZealandO’Brien and Stout, 1978
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Understanding Carbon Storage and Turnover•The balance between inputs and outputs
Soil Organic Matter
Inputs Outputs
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The Model
DOM
vDOM
kDOM
Concentration
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Model Formulation for DRDSC(Decadally Reactive Deep Soil C)
• Mass (g/m2)
• Downward Transport (cm/yr)
• First Order Loss Coefficient (yr-1)
• E-folding Depth (cm)
• No interactions with other 3 pools
• Is DRDSC from roots or dissolved organic matter (DOM)?– Progressive enrichment in most profiles– Below rooting zone
![Page 9: Significant Bomb 14 C Enrichment in Deep Soil: A Previously Unrecognized Decadal C Pool? W. Troy Baisden and Roger L Parfitt Landcare Research, Palmerston.](https://reader038.fdocuments.in/reader038/viewer/2022103022/56649cb65503460f9497b908/html5/thumbnails/9.jpg)
Data Assimilation via a Genetic Algorithm
• Evolves a chromosome of parameter values toward the best value for the model fit (based on an ‘objective function’)
• Inefficient but searches parameter space on both sides of the bomb-C spike
• Monte-Carlo style variation in 14C and %C data• Parameter uncertainty estimated from Monte-Carlo
– Greater of:• Standard deviation of best fits with data PDFs• Difference between best fit with and without PDFs included
• Emphasizing fitting DRDSC pool sizes
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Koputaroa Soil, New Zealand
14C (per mil)
Cu
mla
tive
So
il M
ass
(g c
m-2)
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Soil Organic Carbon (SOC) Pools Estimated by the ModelSite Max.
DepthIncluded
inAnalysis
(m)
Total SOC
(MgC/ha)
SOCwith turnover <100 yr
(MgC/ha)
DRDSC
(MgC/ha)
Koputaroa 0.8 148±4 81±4 10±3Judgeford 1.0 192±10 131±7 10.3±0.7*
TurlockLake
1.1 33±2 13±1 4.7±3.3
Riverbank 3.6 39±3 12±2 9.0±1.3*Model appears to underestimate DRDSC pool size.
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Model-Estimated Soil Organic Carbon (SOC) PoolsSite Max.
DepthIncluded
inAnalysis
(m)
Ratio ofDRDSC toTotal SOC
Ratio ofDRDSC toSOC withturnover<100 yr
Koputaroa 0.8 0.07±0.02 0.13±0.04Judgeford 1.0 0.054±0.005* 0.078±0.008*
TurlockLake
1.1 0.14±0.10 0.37±0.27
Riverbank 3.6 0.23±0.05 0.74±0.05*Model appears to underestimate DRDSC pool size.
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DRDSC as a Fraction of Total SOC
•10-20% of Deep Soil C has Decadal Dynamics
•Possibly increasing with Depth?
•Better understanding of DOC needed!
•10-20% of Deep Soil C has Decadal Dynamics
•Possibly increasing with Depth?
•Better understanding of DOC needed!
Koputaroa