Fig. 5: Influence of weathering congruency on organic matter decomposition rate and the priming effect (PE).

a Indirect linkages between weathering congruency and the priming effect at 10 cm. Normalized Si concentration/Na concentration ([Si]/[Na]_norm) proxies for weathering congruency, with higher values denoting greater weathering congruency. Four weathering congruency groups are recognized, i.e., low to high weathering congruency group, high weathering congruency group, high to low weathering congruency group, and low weathering congruency group. In most cases, organic matter decomposition rate covaries positively with weathering congruency. b Crossplots of organic matter decomposition rate corrected dissolved inorganic carbon (DIC) fluxes (f_DIC-corr) and CO₂ fluxes (f_CO2) vs. [Si]/[Na]_norm for the four weathering congruency groups. c Crossplots of organic matter decomposition rate f_DIC-corr and f_CO2 vs. [Si]/[Na]_norm using a compiled dataset from (b). d Direct influence of weathering congruency on the priming effect. For each depth, the periods for evaluation were selected from Fig. 3 and Supplementary Figs. 7–9 based on similar changes in DOM optical properties to that of “fresh” DOM-induced priming-effect periods without notable change in weathering congruency. f_DIC-corr generally covaries positively with weathering congruency. For example, in the topsoil, a 51% decrease of weathering congruency leads to a 41% decrease of f_DIC-corr, resulting in ~137 mg C m⁻² yr⁻¹ decrease of the priming effect.