Fig. 4

Relationships between change in soil pH and initial pH across five plantation tree species. a Plotting of change in soil pH (CIP) against initial soil pH for each of the five plantation species. Solid lines indicate the ordinary least squares (OLS) fit of the linear equation (CIP = a*pH+b, where pH indicates the pH of the control group) for each of the five plantation species (the colors are the same as the legend in b) and all the species pooled together. b The dependence of mean CIP on initial soil pH across the five plantation species. Mean CIP is averaged for each unit of initial soil pH. Error bars indicate standard errors. Independent sample t-tests with false discovery rate (FDR) correction were conducted to compare data of each group with 0. Symbols *, **, and *** indicate that the null hypothesis could be rejected at a significance level of 0.05, 0.01, and 0.001, respectively. The inset shows the results of two-way ANOVA on the effect of initial soil pH and species on CIP. Interaction indicates initial soil pH × species