Physical location in the tree during forest fire influences element concentrations of bark-derived pyrogenic carbon from charred jack pines (Pinus banksiana Lamb.)

Forest fires create pyrogenic carbon (PyC), which is present in charred biomass and whose characteristics can vary within an individual fire. The purpose here was to investigate the influence of position in a tree on post-fire element concentrations and ratios from charred Pinus banksiana Lamb. tree bark after a stand-replacing prescribed burn in Michigan, USA. We felled five fire-killed trees and collected charred bark from the main tree stem at the base and upper crown and from inner and outer crown locations, and analyzed bark samples for element concentrations. N and H concentrations were greater in bark from the crown than from the tree base, whereas there were no differences in C or O concentrations. There were no statistically significant differences (at p < 0.05) in element concentrations between the inner and outer crown. Van Krevelen diagrams indicated relatively greater charring in bark from the tree base than bark from the tree crown, and in bark from the inner crown than the outer crown. The study shows that physical location in a tree influences PyC characteristics and provides further evidence of the variability that exists in the physicochemical properties of natural PyC material.