Details
| Original language | English |
|---|---|
| Pages (from-to) | 2183-2207 |
| Number of pages | 25 |
| Journal | Soil Biology and Biochemistry |
| Volume | 39 |
| Issue number | 9 |
| Publication status | Published - Sept 2007 |
| Externally published | Yes |
Abstract
Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated. The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm-3) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.
Keywords
- Conceptual model pools, Mean residence time, Organo-mineral interactions, Physical soil fractionation, Recalcitrance, Spatial inaccessibility, Turnover time, Wet chemical fractionation
ASJC Scopus subject areas
- Immunology and Microbiology(all)
- Microbiology
- Agricultural and Biological Sciences(all)
- Soil Science
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In: Soil Biology and Biochemistry, Vol. 39, No. 9, 09.2007, p. 2183-2207.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - SOM fractionation methods: Relevance to functional pools and to stabilization mechanisms
AU - von Lützow, Margit
AU - Kögel-Knabner, Ingrid
AU - Ekschmitt, Klemens
AU - Flessa, Heinz
AU - Guggenberger, Georg
AU - Matzner, Egbert
AU - Marschner, Bernd
N1 - Funding information: This investigation was financially supported by the priority program 1090 “Soils as sinks and sources for CO 2 —mechanisms and regulation of carbon stabilization in soils” of the Deutsche Forschungsgemeinschaft (DFG). We thank two anonymous reviewers for their constructive advice.
PY - 2007/9
Y1 - 2007/9
N2 - Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated. The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm-3) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.
AB - Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated. The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm-3) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.
KW - Conceptual model pools
KW - Mean residence time
KW - Organo-mineral interactions
KW - Physical soil fractionation
KW - Recalcitrance
KW - Spatial inaccessibility
KW - Turnover time
KW - Wet chemical fractionation
UR - http://www.scopus.com/inward/record.url?scp=34250371434&partnerID=8YFLogxK
U2 - 10.1016/j.soilbio.2007.03.007
DO - 10.1016/j.soilbio.2007.03.007
M3 - Article
AN - SCOPUS:34250371434
VL - 39
SP - 2183
EP - 2207
JO - Soil Biology and Biochemistry
JF - Soil Biology and Biochemistry
SN - 0038-0717
IS - 9
ER -