Land use change is one of the anthropogenic interventions thatmay induce substantial modifications to both the quantity andquality of soil organic matter (SOM). Soils from three cultivatedareas (two types of rainfed upland and one irrigated lowland)and two forests (subtropical managed and temperate unmanaged)in a midhill watershed of Nepal were studied to assess the effectof land use change on SOM quality. Bulk SOM was analyzed usingsolid-state ¹³C nuclear magnetic resonance (NMR) and fractionatedby acid hydrolysis into pools with different chemical compositionand, thus, different tendencies to decomposition. The NMR analysisshowed a clear prevalence of O-alkyl C over alkyl C and aromaticC, with major differences between both soils and two depth intervalsof the same soil (0–20 and 20–40 cm). Acid hydrolysisrevealed that the labile C pool is larger in the 0- to 20- thanthe 20- to 40-cm soil depth of each land use. Labile C was largerin the temperate unmanaged forest and the irrigated cultivatedland than in the other soils at both soil depths. Of the cultivatedrainfed soils, the recently reclaimed soil contained less labileC than the historically cultivated soil, while the labile Cin the irrigated soil exceeded that in both rainfed soils. Theresults suggest that changes in land use from forest to cultivationand the irrigation of the cultivated land may significantlyaffect not only the quantity but also the quality of the SOMand, more importantly, its chemical recalcitrance to degradation.As a consequence, any future decisions regarding land managementin the fragile mountain areas of Nepal should be carefully consideredwith respect to the nature of the SOM.