Fig. 5. Carbon-13 cross-polarization with magic-angle spinning nuclear magnetic resonance (CPMAS NMR) spectra for selected 2- to 8-mm mineral soil fraction (MIN-ROOT) samples, illustrating variation along Principal Component (PC) 1 and PC 2 (a). The central region with six samples in close proximity is expanded in (b). Inserts show dipolar dephasing (DD) spectra for selected samples. Strong features from wood, tannins, and char are indicated by W, T, and C, respectively.

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