Fig. 1: Spatial and temporal patterns of wood δ¹⁵N and N deposition across Sweden.

a, Spatial distribution of independent samples (n = 1609) across 4 Nr deposition regions spanning Sweden’s north–south gradient, representing increasing deposition rates from lowest (north) to highest (southwest). b, Temporal change in total wet plus dry N deposition (kg ha⁻¹ yr⁻¹) for samples across the regions. c–j, Temporal linear regression trends in stemwood δ¹⁵N (‰) for P. sylvestris (c,e,g,i) and P. abies (d,f,h,j) from 1951 to 2017 in each of the Nr deposition regions: north (c,d), central (e,f), southeast (g,h) and southwest (i,j). All relationships are significant (P < 0.001) except for P. abies in the southeast region (h), where the non-significant relationship is shown as a dashed line. Lowercase bold letters in c–j denote significant differences in regression slopes among regions, within each species (α = 0.05). Shading in b indicates the 95% confidence interval. A small horizontal offset was applied to time plots c–j to increase the visibility of points (see ‘Statistical methods’). Data sources are cited in Methods. Sweden boundary map in a from Lantmäteriet under a Creative Commons licence CC0 1.0.