Non-cellulosic neutral sugar contribution to mineral associated organic matter in top- and subsoil horizons of two acid forest soils

We investigated the polysaccharide composition of bulk and mineral-bound (density fractions >2 g cm−3) organic matter in topsoil and subsoil horizons of a Podzol and a Cambisol. Total sugar contents were generally higher in the Cambisol than in the Podzol. For most horizons of both soils, the sugars were enriched in the mineral-bound organic matter fraction. This fraction showed a monosaccharide distribution typical for microbial sugars, whereas in bulk soil horizons higher contributions of plant-derived sugars were observed. A strong relationship with the 14C activity of the dense fraction suggests that microbial-derived polysaccharides are most likely stabilised preferentially by mineral interactions compared to plant-derived polysaccharides.