Fig. 1: Overview of the three methods for timber tracing in this study and their drivers of geographic variation.

Possible drivers of geographic variation shown as examples are: 1. For SNPs: former forest refugia during cold Pleistocene glaciation cycles with refugia in dark and forest cover in light green, adapted from Allen et al.⁸¹, 2. For stable isotopes: the oxygen isotope signal in rainwater, with higher rainwater δ¹⁸O in lighter blue⁸² and 3. For multi-element analysis: soil clay content ranging from high clay % in green, mid-levels of clay % in yellow and low clay % in pink⁸³.