Fig. 3
From: An added boost in pyrogenic carbon when wildfire burns forest with high pre-fire mortality
Differences in pyrogenic carbon (PyC) for charred bark and wood from beetle-killed snags and fire-killed snags that were sampled at the Pole Creek Fire (2012), Oregon, USA, in June 2018. A Welch t-test for unequal variance was performed to test for a difference in mean Benzene Polycarboxylic Acid (BPCA) concentrations between beetle-killed (n = 6) and fire-killed (n = 6) snags. Each panel shows the mean (point), raw data split as bark (diamonds) and wood (triangles) samples, and the boxplot distribution. (A) Beetle-killed snags had a greater concentration of PyC than fire-killed snags, with a difference of 21.8 g BPCA per kg Carbon (C; 95% confidence interval = 10.6 to 33, P = 0.003) and (B) a difference of 15 g BPCA per kg material (95% confidence interval = 6.2 to 23.8, P = 0.006). (C) For the Aromatic Condensation Index (ACI), there was no difference between beetle-killed and fire-killed snags. However, the low concentration of BPCA in fire-killed snags (A, B) suggests that the overall concentration of benzene hexacarboxylic acid (B6CA) in fire-killed snags is lower than in beetle-killed snags. The difference in PyC concentrations between beetle-killed and fire-killed snags demonstrates an important compound effect of short-interval beetle–fire disturbances