Spectral responses to labile organic carbon fractions as useful soil quality indicators across a climatic gradient

•LF material had similar spectral features across different climates.•SOM content did not vary in relation to spectral characteristics of LF.•Aliphatic CH and polysaccharides were related to high SOC, POXC, and aggregation.•Spectral features related to labile fractions are suitable to assess soil quality.•POXC is sensitive to climate changes and useful for a rapid estimation of SOC.