Title: Density fractionation of forest soils: methodological questions and interpretation of incubation results and turnover time in an ecosystem context

Author: Crow, Susan E.; Swanston, Christopher W.; Lajtha, Kate; Brooks, J. Renee; Keirstead, Heath

Year: 2007

Publication: Biogeochemistry. 85: 69-90.

Abstract: Soil organic matter (SOM) is often separated by physical means to simplify a complex matrix into discrete fractions. A frequent approach to isolating two or more fractions is based on differing particle densities and uses a high density liquid such as sodium polytungstate (SPT). Soil density fractions are often interpreted as organic matter pools with different carbon (C) turnover times, ranging from years to decades or centuries, and with different functional roles for C and nutrient dynamics. In this paper, we discuss the development and mechanistic basis of common density-based methods for dividing soil into distinct organic matter fractions. Further, we directly address the potential effects of dispersing soil in a high density salt solution on the recovered fractions and implications for data interpretation.