Chemical and carbon isotopic dynamics of grass organic matter during litter decompositions: A litterbag experiment

•Better preservation of aromatic and alkyl carbon than celluloses and carbohydrates.•CPI and ACL of n-alkanes remained relative constant despite 90% C degraded.•90% of litter mass was lost for three C4 species (Setaria viridis, Eleusine indica, Amaranthus retroflexus) and one C3 species (Erigeron speciosus). The solid state 13C NMR spectra showed that mean proportion of aromatic and alkyl carbon increased from ca. 10% to 15% and ca. 10% to 20%, respectively, whereas that of O-alkyl carbon substantially decreased from ca. 70% to 50%. The carbon preference index and average chain length of n-alkanes remained relatively constant, whereas the carbon isotopic compositions of long chain n-alkanes varied