Fig. 5: Synchrotron-based spectromicroscopic analysis of microaggregates (53–250 µm) and mineral fractions (<53 µm) in Control+Recent and Historical+Recent soils.
From: Microspectroscopic visualization of how biochar lifts the soil organic carbon ceiling
a Average soft X-ray (SXR) spectra of microaggregates and mineral fractions from Historical+Recent and Control+Recent plots (n = 9, CV < 3%), featuring quinones, aromatic C, aliphatic C, and carboxylic C. b Semi-thin (200 nm) sections of free water-stable microaggregates and mineral fractions isolated from Historical+Recent and Control+Recent plots analyzed using synchrotron-based infrared-microspectroscopy (IRM). Spectral maps showing the distribution of polysaccharide-C (1035 cm−1), aromatic-C (1600 cm−1), aliphatic-C (2920 cm−1), and clay mineral-OH (3650 cm−1) obtained from 64 co-added scans, overlaid on optical micrographs of the semi-thin sections. Bars, 50 µm. Pie charts display normalized optical proportions of the four features analyzed by an image processing pipeline (Supplementary Fig. 10 and Supplementary Table 12). c Hierarchical clustering dendrogram indicating similarity relationships between C functional groups from SXR (first derivatives), and their distribution from IRM or belowground C retention (Fig. 3a, b) across biochar treatments.
