Impact of land-use on soil organic matter quality in south-western Australia—characterization with 13C CP/MAS NMR spectroscopy

The influence of change in land-use from native vegetation to pasture (20–71 yr after conversion), and subsequent change from pasture to eucalypt plantation (7–10 yr after conversion) on soil organic matter quality was investigated using 13C CP/MAS NMR spectroscopy. We studied surface soil (0–10 cm) from six sites representing a range of soil and climate types from south-western Australia. Total C in the samples ranged from 1.6 to 5.5%, but the relative proportions of the four primary spectral regions (alkyl, O-alkyl, aromatic and carboxylic) were similar across the sites, and changes due to land-use at each site were relatively minor. Main impacts of changed land-use were higher O-alkyl (carbohydrate) material under pasture than under native vegetation and plantation (P=0.048), and lower aromatic C under pasture than under native vegetation (P=0.027). The decrease in aromatic C in pasture soils was related to time since clearing.