In:
Biogeosciences, Copernicus GmbH, Vol. 16, No. 7 ( 2019-04-05), p. 1401-1410
Abstract:
Abstract. Minerals, particularly clay-sized minerals, protect soil
organic matter (SOM) from decomposition by microorganisms. Here we report
the characterization of SOM and the associated minerals over decades of
biodegradation, in a French long-term bare fallow (LTBF) experiment started
in 1928. The amounts of carbon (C) and nitrogen (N) in the study area declined over time for
six fractions (sand, coarse silt, fine silt, coarse clays, intermediate
clays, and fine clays). The C:N ratios of SOM associated with silt fractions
remained constant, whereas the ratios significantly decreased in clays, reaching
very low values in intermediate and fine clays (C:N 〈 5) after
8 decades of LTBF conditions. X-ray absorption spectroscopy revealed the following: (i) bulk-scale
SOM chemical speciation remained almost constant; (ii) submicron
particulate OM was present in coarse clays, even after 79 years of LTBF
conditions; and (iii) illite particles became progressively SOM-free with time, whereas mixed-layer
illite/smectite and smectites were always associated with OM
throughout the bare fallow treatment. In summary, these results suggest that
clay-sized minerals preferentially protect N-rich SOM and that smectites and
mixed-layer illite/smectite seem to protect associated OM more effectively
than pure illites.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-16-1401-2019
DOI:
10.5194/bg-16-1401-2019-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2019
detail.hit.zdb_id:
2158181-2
