To enable rapid, non-destructive analysis and functional classification of karst calcareous soils in Shilin County, Kunming, this study acquired mid-infrared attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectra in the 4000-900\cmi{} range from 409 soil samples. After standardized preprocessing, the samples were preliminarily partitioned into four spectral groups by K-means clustering, and a partial least squares discriminant analysis (PLS-DA) model was constructed. Variable importance in projection (VIP) scores were further used to identify key spectral features distinguishing the classes. The spectra were dominated by peaks at 3620, 1650, and 1020\cmi{}, and no obvious... More >