Fig. 5

Inset: Fire history record for the studied landscape in north-central Pennsylvania, USA. Horizontal lines represent the tree-ring record for individual trees; bold vertical ticks on horizontal lines indicate fire scar years. On the left ends of lines, vertical ends indicate pith years, and diagonal ends indicate inner-most ring year (unknown number of rings missing to pith). On the right ends of lines, vertical ends indicate bark years while diagonal ends indicate outer-most ring years (unknown number of rings missing to bark). At the bottom of the graph, a composite record of all fire event years recorded at the site is shown. The inset figure on the left shows all trees (n=267) included in the study; the central graph shows the oldest 50 trees in record (marked by black dashed line in the inset). The four lowest lines (with sample no. labels) in the central graph represent the four trees sampled in the course of previous research at the site (Marschall et al. 2019) that previously did not crossdate due to insufficient overlap with existing local tree-ring growth chronologies. The red dashed line encompasses the 10 oldest trees collected in subsequent sampling efforts, which allowed for the four previously undatable trees to be crossdated