2:15 PM - 2:30 PM
[MIS06-15] Can we comprehend organo-mineral associations occurring at different levels of soil aggregate hierarchy? A case study using a volcanic-ash soil (Andisol)
Keywords:soil carbon, microstructure, organo-mineral interaction
First, we demonstrated that the isolation of low-density fraction, a readily accessible OM outside of aggregates, was necessary to examine the factors controlling decomposition temperature sensitivity. Second, using sequential density fractionation, we isolated soil aggregates that are resistant to mechanical shaking and showed density-dependent changes in the chemistry of OM (d13C, d 15N, d14C as well as C:N ratio) and that of mineral phases (organically complexed metals and short-range-ordered minerals). Third, we found the particle size dependent changes in organo-mineral chemistry in the same soil only after achieving maximum dispersion of these aggregates by sodium saturation followed by sonication. Clay-sized particles after the dispersion, however, still showed aggregated features by SEM and TEM. We will discuss possible factors controlling OM stabilization in these fractions and the presumed relationship between the fractions obtained from different levels of aggregate hierarchy (sonication-resistant particles vs. shaking-resistant aggregates).