Testing the differentiation of relative root distributions among species
To increase statistical power, the comparisons of relative root distributions were focused on the 53 most common species with occurrences ≥ 15 cubes. For a given species, we calculated the averaged value of relative root abundance in each soil zone of that species and tested whether soil zone significantly influenced the means of relative root abundance using a one-way Welch’s ANOVA. Pairwise comparisons of the means of relative root abundance among soil zones was performed using the Games-Howell Post-Hoc Test. Finally, we categorized the 53 species into different groups based on their relative root distributions using clustering analysis.