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Stabilization of dissolved organic matter by sorption to the mineral soil

Title data

Kalbitz, Karsten ; Schwesig, David ; Rethemeyer, Janet ; Matzner, Egbert:
Stabilization of dissolved organic matter by sorption to the mineral soil.
In: Soil Biology & Biochemistry. Vol. 37 (2005) Issue 7 . - pp. 1319-1331.
ISSN 0038-0717
DOI: https://doi.org/10.1016/j.soilbio.2004.11.028

Abstract in another language

The main process by which dissolved organic matter (DOM) is retained in forest soils is likely to be sorption in the mineral horizons that adds to stabilized organic matter (OM) pools. The objectives of this study were to determine the extent of degradation of sorbed OM and to investigate changes in its composition during degradation. DOM of different origins was sorbed to a subsoil and incubated for 1 year. We quantified mineralized C by frequent CO2 measurements in the headspace of the incubation vessels and calculated mean residence times by a double exponential model. Mineralization of C of the corresponding DOM in solution was used as a control to estimate the extent of DOM stabilization by sorption. Changes in the composition of sorbed OM during the incubation were studied by spectroscopic (UV, fluorescence) and isotope (13C, 14C) measurements after hot-water extraction of OM.The fraction of sorbed organic C mineralized during the incubation was only one-third to one-sixth of that mineralized in solution. The mean residence time of the most stable OM sample was estimated to increase from 28 years in solution to 91 years after sorption. For highly degradable DOM samples, the portion of stable C calculated by a double exponential model nearly doubled upon sorption. With less degradable DOM the stability increased by only 20% after sorption. Therefore, the increase in stability due to sorption is large for labile DOM high in carbohydrates and relatively small for stable DOM high in aromatic and complex molecules. Nevertheless, in terms of stability the rank order of OM types after sorption was the same as in solution. Furthermore, the extent of sorption of recalcitrant compounds was much larger than sorption of labile compounds. Thus, sorptive stabilization of this stable DOM sample was four times larger than for the labile ones. We conclude that stabilization of OM by sorption depends on the intrinsic stability of organic compounds sorbed. We propose that the main stabilization processes are selective sorption of intrinsically stable compounds and strong chemical bonds to the mineral soil and/or a physical inaccessibility of OM to microorganisms. The UV, fluorescence and 13C measurements indicated that aromatic and complex compounds, probably derived from lignin, were preferentially stabilized by sorption of DOM. The 13C and 14C data showed that degradation of the indigenous OM in the mineral soil decreased after sorption of DOM. We estimated DOM sorption stabilizes about 24 Mg C ha−1 highlighting the importance of sorption for accumulation and preservation of OM in soil.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER20657
Keywords: 13C; 14C; Dissolved organic matter; Fluorescence spectroscopy; Hot-water extraction; Mineralization; Sorption; Stabilization; UV/VIS spectroscopy
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Chair Soil Ecology
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Former Professors > Chair Soil Ecology - Univ.-Prof. Dr. Egbert Matzner
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 500 Science
Date Deposited: 11 Sep 2015 06:34
Last Modified: 11 Sep 2015 06:34
URI: https://eref.uni-bayreuth.de/id/eprint/19205