Fig. 3: Root bimodality explained by within-site depth-level factors.
From: A continental scale analysis reveals widespread root bimodality
a, b Illustration of a unimodal distribution (a) and a bimodal distribution (b) of property Y (root biomass in this case). Three depths derived from bimodal distribution are highlighted with filled dots: primary mode depth (D0), antimode depth (D1), and secondary mode depth (D2) (Methods). Using a given property value (Y) at depth D1 and D2, we can calculate ɸ as the ratio of Y(D2) and Y(D1). c Comparison of ɸ (root biomass) across unimodal (n = 35) and bimodal (n = 9) sites (two-sided Welch’s t-test, p = 2.4e-06). d Comparison of ɸ (soil nitrogen concentration) across unimodal (n = 27) and bimodal (n = 7) sites (two-sided Welch’s t-test, p = 0.013). Note that ɸ is unitless. In each box plot, the lower and upper bounds of the whiskers denote minima and maxima, the center line denotes the median, and the lower and upper bounds of the boxes represent the 25% and 75% quantiles, respectively. Source data are provided as a Source Data file.
