Fig. 2: Influence of catchment size, river-reach biome and lithology on 14C in river DIC, CO2 and CH4.
From: Old carbon routed from land to the atmosphere by global river systems
a, Normalized F14Catm values for DIC, CO2 and CH4 separated by catchment size, either ≤10 km2 or >10 km2 (Methods and Supplementary Fig. 6); statistical difference is indicated by the P value (shown at the top) derived from an unpaired two-sample Wilcoxon test. b, F14Catm values separated by lithology of the river reach (within a 1-km2 radius of the sampling location) as defined in HydroATLAS and binned for comparison (Methods and Supplementary Fig. 3); statistically significant differences are indicated by P values when comparing across all three lithologies using a Kruskal–Wallis test (shown at the top) and unpaired two-sample Wilcoxon tests (P values and horizontal bars). c, F14Catm values separated by the biome of the river reach (Methods and Supplementary Fig. 2); lowercase letters indicate statistically significant differences (P < 0.05) using a Kruskal–Wallis test (P value shown at the top) and Conover–Iman post hoc. The horizontal black line in each panel represents the mean-normalized F14Catm for all samples; box and whisker dimensions follow Fig. 1b.
