Folks,
I am characterizing particulate plant derived organic matter input to
the soil. The approach I have taken is planting C3 plants into a
soil with a long C4 history. The particulate organic matter in the
soil at the start of the experiment had a del vPDB signature of
-14.000 and the new C3 input has a del vPDB of -28.000. My problem
is that the protocol for isolating the organic matter requires that I
co-collect the organic matter with the sand fraction of the soil,
which contains about 18% carbonate with a del vPDB of 0. I'm
wondering if anybody can help me with a three source mixing model
that can be run using only one isotope? Using a separate analysis of
the soil I can calculate the amount of carbonate in each sample but I
need to determine the proportion of each plant source (C3 or C4) in
the remaining organic carbon.
Ideally I would have removed the carbonate prior to isotopic analysis
but at the time of sample prep I didn't realize how much of an issue
the carbonate would be.
Thanks
jude
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Jude Maul
Department of Horticulture
Cornell University
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(607)255-0883 (office)
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