A novel pathway of soil organic matter formation by selective preservation of resistant straight-chain biopolymers: chemical and isotope evidence

Abstract A resistant soil organic residue, “humin”, has been analyzed by solid-state 13 C-NMR and pyrolysis followed by molecular and 13 C determination of the pyrolysate alkane–alkene fraction. The results show the occurrence of highly aliphatic, straight-chain biopolymer material as a substantial part of soil organic matter. They confirm the hypothesis by which a part of soil organic matter can be formed by selective preservation of resistant highly aliphatic microbial polymers. This pathway is additional to the longstanding neogenesis hypothesis involving recondensation of small polar molecules such as amino acids, carbohydrates and phenols.