Fig. 4 | Main contorls over the SOM formation
efficiency identified using structure equation modelling. Optimized
structure equation model shows no effects of litter chemistry and three
independent (P = 0.16, n = 18) pathways from clay minerals to the
SOM formation efficiency. Path coefficient (k p),
with a significance at P < 0.05 (*) or P< 0.05 (**) and the proportion of the variance
(R2) are presented for each pathway, with the
line width proportional to kp . The chemical
composition of litter residues is reflected by the score of the second
principal component of principal component analysis of functional C
groups estimated by 13C NMR (Fig. 2) as it
demonstrates the effects of clay mineral types irrespective of litter
type.
Fig. 5 | Mineral-organic association effects on the
X-ray diffractograms of clay minerals. a, b , Original minerals (thick
lines) before incubation and model soils without
H2O2 treatment (thin lines) and with
H2O2 treatment (dotted lines) after
incubation with maize and soya litter.
Fig. 6 | Quantification and application of
mineral-protection strength. a, Cumulative respiration measured
(symbols) and modeled (lines) using the novel model describing the
mineral-protection strength (δ ) (inserted equation). Error bars
represent standard errors (n=3). b, Correlation between SOM
formation efficiency and mineral-protection strength (δ ).