Fig. 1 Average concentration (bars) of lignin-derived phenols (VSC), as well as phenolic acid to aldehyde ratios (curves) of the syringyl (ac/al)_S and vanillyl (ac/al)_V structural units in particle-size fractions of 18 topsoils in the native grasslands. The symbol *** indicates that VSC is significantly higher compared to the next finer fraction at the P < 0.001 probability level of significance. The symbol ¹ indicates that significant difference is obtained only when ANOVA is conducted with natural log-transformed VSC values. The error bars result from variations in VSC concentrations of a respective fraction across the prairie