The forgotten part of carbon cycling: Organic matter storage and turnover in subsoils [SUBSOM]
Abstract
In the past, carbon flux measurements and modelling have mostly considered the topsoil where C-concentrations, root densities and microbial activities are generally highest. However, depending on climate zone and land use, this soil compartment contains only 30-50% of the C-stocks of the first meter. If the deeper subsoil down to 3 m is also considered, the contribution of topsoil carbon stocks to total soil C-pools is only 20-40%. Another distinct property of subsoil organic matter is its high apparent 14C age. The 14C age of bulk soil organic matter below 30 cm depth generally increases continuously indicating mean residence times of several 103 to 104 years. Large pool size and high radiocarbon age suggest that subsoil OM has accumulated at very low rates over very long time periods and therefore appears to be very stable. In a review, several hypotheses for explaining why subsoil SOM is so seemingly old and inert are presented. Then a recently granted German research unit consisting of 9 subprojects from all soil science disciplines is introduced, which addresses these questions using field measurements of C-fluxes, 14C analyses and conducting field and lab experiments. 40-60% of soil C-pools are found below 40 cm depth (Data from Jobbagy & Jackson 2000).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B11J..01M
- Keywords:
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- 0486 BIOGEOSCIENCES Soils/pedology;
- 0414 BIOGEOSCIENCES Biogeochemical cycles;
- processes;
- and modeling;
- 0428 BIOGEOSCIENCES Carbon cycling