Extended Data Fig. 5: Drought response of above- and belowground net primary production of trees.

The upper panels a) and d) show the annual values of above- and belowground net primary production of trees (ANPP_t and BNPP_t, respectively) for the baseline period 2016-2017 (BL_16–17) and the drought year 2018 (D₁₈). The middle panels b) and e) show the absolute anomalies (∆X), while the lower panels c) and f) display the relative anomalies (δX). Circular open symbols indicate the values for each forest stand, while circular closed symbols indicate the means for each of the stand age classes, including initiation (I), young (Y), middle-aged (Ma), mature (M), and old-growth (O). The horizontal and vertical bars represent the 95% confidence intervals, while the solid lines show the best-fit regressions. The equation form and coefficient of determination (R²) of the linear regressions are also presented. Equations and associated goodness-of-fit statistics are derived from the individual forest stand data (n = 49). Box plots of the annual values along with the absolute and relative anomalies are also shown. The boxes represent the 25^th (bottom) and 75^th (top) percentiles, the central line the median, and the cross the mean. Whiskers above and below the boxes denote data within 1.5 times of the interquartile range, with outliers presented as individual points. The values show the means ( ± 95% confidence intervals) of ANPP_t and BNPP_t, as well as their absolute and relative anomalies. The p-values for the non-parametric Kruskal–Wallis rank sum test comparing the differences between the means of stand age classes and BL_16–17–D₁₈ periods are also shown. The horizontal dashed lines indicate the negative-to-positive transition for both the absolute and relative anomalies.