There's another possibility that I have been mulling over. If the water
source (and del 18O) to plants changes for some reason, the del 18O of leaf
and root litter should also change. As others pointed out, respired CO2
will equilibrate quickly with soil H2O, so I doubt such a signal would be
interpretable. But the remaining organic matter should still reflect the
18O signature of the litter (how faithfully?), potentially enabling one to
look at the del 18O of various soil organic matter pools and to quantify
turnover rates of various SOM fractions. I'm new to this, so I'm not sure
if this would be feasible (detection limits?), but am curious if others have
had similar thoughts and dismissed them for one reason or another.
Cheers,
dv
David W. Valentine, Ph.D., Assistant Professor of Forest Soils
Department of Forest Sciences, P.O. Box 757200
University of Alaska, Fairbanks AK 99775-7200
tel (907) 474-7614, fax (907) 474-6184
[log in to unmask] <mailto:[log in to unmask]> , http://www.lter.uaf.edu/~davev
<http://www.lter.uaf.edu/~davev>
> -----Original Message-----
> From: Stable Isotope Geochemistry [mailto:[log in to unmask]]On
> Behalf Of Rebecca Hood
> Sent: Wednesday, July 05, 2000 1:26 AM
> To: [log in to unmask]
> Subject: 18o in organic matter again
>
>
> Dear all
>
> Thanks for the responses so far, very useful. But maybe
> I didn't explain myself too well (as ever) the idea is to grow, plants in
> fairly highly labeled 18O water then apply that material dried to soil and
> look at its turnover, residence, breakdown etc. The material being
> significantly higher enrichment than natural abundance levels interference
> from silicates etc may not be such a big problem. The key question is at
> higher enrichments would the exchange rates between H20 and CO2 preclude
> this as a useful technique????
> Just bouncing ideas !!!
> Thanks again.......
> Dr Rebecca Hood
> Soil Science Unit
> FAO/IAEA Agriculture and Biotechnology Laboratory,
> IAEA Laboratories
> A-2444 Seibersdorf
> Austria
> Tel 00 43 1 2600 28271
> Fax 00 43 1 2600 28222
>
> http://www.iaea.org/programmes/nafa <http://www.iaea.org/programmes/nafa>
>
> http://www.fao.org <http://www.fao.org>
> Symposium Web site:
> http://www.iaea.org/programmes/nafa/d1/mtc/00_it.html
>
|
