Rooting depth (log-scale) vs. (A) mean annual rainfall, (B) soil texture (SI Appendix, Table S1A), (C) depth of soil barriers, (D) growth form (SI Appendix, Table S1B), (E) genera (SI Appendix, Table S1C), and (F) WTD, giving Pearson correlation coefficient r (on original data) and sample size N out of 2,200 observations.