Methodological development is an important part of advancing science. In our lab, we develop and refine methods aimed at the physical separation of different pools of organic matter in soils. Physical separation fractionates an intial soil sample into a series of portions or fractions differing in size, density and/or aggregation strength.
Physical separation is well-suited to isolate fractions that are relatively homogeneous in terms of organic matter content and mineralogy. Soil organic matter in each fraction tends to have a unique stability or turn-over time due to differing levels of protection by interaction with soil minerals. A common fractionation scheme involves the separation of so-called ‘light fractions’, which interact rather weakly with the mineral phase, from a number of ‘heavy fractions’ which contains organic matter strongly adsorbed to different soil minerals.
By allowing for the isolation of organo-mineral complexes of relative compositional homogeneity, physical fractionation methods provide direct evidence for the type and diversity of organo-mineral interactions in natural soils. Heavy fractions resulting from physical fractionation may be subsequently analysed by a range of methods to provide detailed information on the nature of both the organic and the mineral component of the organo-mineral complex. This information will allow us to better understand controls on organic matter persistence in natural soils.
Active project members
Stéphanie Grand (project lead)
Fanny Viret
David Sebag
Websites
Thünen Institute of Climate-Smart Agriculture (2018) SOMfractionation: a website guiding students and scientists on soil organic matter fractionation methods. https://www.somfractionation.org/physical-meth/density-sollins-2/
Relevant publications
Viret F, Grand S (2019) Combined size and density fractionation of soils for investigations of organo-mineral interactions. Journal of Visualized Experiments 144:e58927. Doi: 10.3791/58927
Popleau C, Don A, Six J, Kaiser M, Benbi D, Chenu C, Cotrufo FM, Derrien D, Gioacchini P, Grand S, Gregorich E, Griepentrog M, Gunina A, Haddix M, Kuzyakov Y, Kühnel A, MacDonald LM, Soong J, Trigalet S, Vermeire M-L, Rovira P, van Wesemael B, Wiesmeier M, Yeasmin S, Yevdokimov I, Nieder R (2018) Isolating soil organic carbon fractions with varying turnover rates – A comprehensive comparison of fractionation methods. Soil Biology and Biochemistry 125:10-26. Doi: 10.1016/j.soilbio.2018.06.025