Title: Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison

Abstract

Fractionation of soil organic carbon (SOC) is crucial for mechanistic understanding and modeling of soil organic matter decomposition and stabilization processes. It is often aimed at separating the bulk SOC into fractions with varying turnover rates, but a comprehensive comparison of methods to achieve this is lacking. In this study, a total of 20 different SOC fractionation methods were tested by participating laboratories for their suitability to isolate fractions with varying turnover rates, using agricultural soils from three experimental sites with vegetation change from C3 to C4 22–36 years ago. Enrichment of C4-derived carbon was traced and used as a proxy for turnover rates in the fractions. Methods that apply a combination of physical (density, size) and chemical (oxidation, extraction) fractionation were identified as most effective in separating SOC into fractions with distinct turnover rates. Coarse light SOC separated by density fractionation was the most C4-carbon enriched fraction, while oxidation-resistant SOC left after extraction with NaOCl was the least C4-carbon enriched fraction. Surprisingly, even after 36 years of C4 crop cultivation in a temperate climate, no method was able to isolate a fraction with more than 76% turnover, which challenges the link to the most active plant-derived carbon pools inmore » models. Particles with density >2.8 g cm^-3 showed similar C4-carbon enrichment as oxidation-resistant SOC, highlighting the importance of sesquioxides for SOC stabilization. The importance of clay and silt-sized particles (<50 μm) for SOC stabilization was also confirmed. Particle size fractionation significantly outperformed aggregate size fractionation, due to the fact that larger aggregates contain smaller aggregates and organic matter particles of various sizes with different turnover rates. An evaluation scheme comprising different criteria was used to identify the most suitable methods for isolating fractions with distinct turnover rates, and potential benefits and trade-offs associated with a specific choice. The study's findings can be of great help to select the appropriate method(s) for fractionation of agricultural soils.« less

Authors:

Poeplau, Christopher  ^[1];

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Don, Axel ^[1]; Six, Johan ^[2]; Kaiser, Michael ^[3]; Benbi, Dinesh ^[4]; Chenu, Claire ^[5]; Cotrufo, M. Francesca ^[6]; Derrien, Delphine ^[7]; Gioacchini, Paola ^[8]; Grand, Stephanie ^[9]; Gregorich, Edward ^[10]; Griepentrog, Marco ^[11]; Gunina, Anna ^[12]; Haddix, Michelle ^[6]; Kuzyakov, Yakov ^[13]; Kühnel, Anna ^[14]; Macdonald, Lynne M. ^[15]; Soong, Jennifer ^[16]; Trigalet, Sylvain ^[17]; Vermeire, Marie-Liesse ^[18] more »; Rovira, Pere ^[19]; van Wesemael, Bas ^[17]; Wiesmeier, Martin ^[20]; Yeasmin, Sabina ^[21]; Yevdokimov, Ilya ^[22]; Nieder, Rolf ^[23] « less

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+ Show Author Affiliations

1. Thünen Inst. of Climate-Smart Agriculture, Bundesallee, Braunschweig (Germany)
2. Swiss Federal Inst. of Technology, Zurich, Zurich (Switzerland). Dept. of Environmental Systems Science
3. Univ. of Kassel, Nordbahnhofstr, Witzenhausen (Germany). Dept. of Environmental Chemistry; Univ. of Nebraska, Lincoln, NE (United States). Inst. for Agriculture and Natural Resources, Dept. of Agronomy and Horticulture
4. Punjab Agricultural Univ., Ludhiana, IN (United States)
5. Univ. Paris-Saclay, Thiverval Grignon (France). UMR Ecosys, UNRA, AgroParisTech
6. Colorado State Univ., Fort Collins, CO (United States). Dept. of Soil and Crop Sciences & Natural Resources Ecology Lab.
7. INRA UR Biogéochimie des Ecosystèmes Forestiers, Nancy (France)
8. Univ. of Bologna, Viale Fanin, Bologna (Italy). Dept. of Agricultural Sciences
9. Univ. of Lausanne, Lausanne (Switzerland). Inst. of Earth Surface Dynamics
10. Agriculture & AgriFood Canada (AAFC), Ottawa, Ontario (Canada). Central Experimental Farm
11. Ghent Univ. Ghent (Belgium). Isotope Bioscience Lab. (ISOFYS), Dept. of Applied Analytical and Physical Chemistry; ETH Zurich, Sonneggstrasse, Zurich (Switzerland). Biogeoscience, Dept. of Earth Sciences
12. Georg-Augist Univ. of Göttingen, Büsgenweg, Göttingen (Germany). Dept. of Agricultural Soil Science; Bangor Univ., Bangor, Gwynedd (United Kingdom). School of Environment, Natural Resources and Geography
13. Georg-Augist Univ. of Göttingen, Büsgenweg, Göttingen (Germany). Dept. of Agricultural Soil Science
14. Technical Univ. of Munich, Freising (Germany). TUM School of Life Sciences Weihenstephan, Chair of Soil Science
15. CSIRO Agriculture & Food, Geln Osmond (Australia). Waite Campus
16. Univ. of Antwerp, Wilrijk (Belgium). Dept. of Biology
17. Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium). Georges Lemaître Centre for Earth and Climate Research, Earth and Life Institute
18. Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium). Earth and Life Inst.
19. Crtr Sant Llorenç de Morunys, Solsona, Catalonia (Spain). Forest Sciences Centre of Catalonia (CTFC)
20. Technical Univ. of Munich, Freising (Germany). TUM School of Life Sciences Weihenstephan, Chair of Soil Science; Bavarian State Research Center for Agricultur, Freising (Germany). Inst. for Organic Farming, Soil and Resource Management
21. Univ. of Sydney, Sydney (Australia). Centre for Carbon, Water and Food, Faculty of Agriculture and Environment, School of Life and Environmental Sciences
22. Inst. of Physicochemical and Biological Problems in Soil Science, Pushchino, Moscow region (Russia)
23. Technische Univ. Braunschweig, Braunschweig (Germany). Inst. of Geoecology,

Publication Date:

2018-10-01

Research Org.:

Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1567132

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Accepted Manuscript

Journal Name:

Soil Biology and Biochemistry

Additional Journal Information:

Journal Volume: 125; Journal Issue: C; Journal ID: ISSN 0038-0717

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; carbon sequestration; carbon stabilization; soil organic matter; fractionation; stable isotopes