2:15 pm - 3:15 pm
849 General Services Building (GSB), General Services Building, University of Alberta, Edmonton AB
Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Stephanie Koroscil. This seminar is open to the general public to attend.
Thesis Topic: The influences of fuel moisture and diameter on pyrogenic carbon production in fine woody debris from three Boreal tree species under simulated surface fire conditions
Wildland fires burn millions of hectares annually, releasing a significant amount of carbon into the atmosphere. Wildland fires also produce pyrogenic carbon – thermally-altered biomass that is highly resistant to decay – which accumulates in fire-affected ecosystems over time. Large wildfires, common in the boreal forest, burn for extended periods and across wide areas; tree species, fuel loading, and fuel moisture are variable between and within these expansive wildfires. Identifying how the physical characteristics of forest fuels relate to the production of pyrogenic carbon is important to understanding how pyrogenic carbon production varies among wildfires. This thesis explores how tree species, stick-diameter, and fuel moisture content affect pyrogenic carbon production in fine woody debris through a laboratory burn study. In this experimental study, fine woody debris from 3 boreal tree species was separated into 5 stick-diameter size classes, conditioned to 3 fuel moisture contents, and burned under simulated surface fire conditions. The overall mean pyrogenic carbon production rate was 5.1% relative to pre-burn sample weight. Mean pyrogenic carbon production rates ranged from 3.9-7.9% among species, 1.3-9.4% among stick-diameter size classes, and 4.5-5.8% among fuel moisture contents. Trembling aspen (Populus tremuloides Michx.) produced significantly more pyrogenic carbon than black spruce (Picea mariana (Mill.); BSP) and jack pine (Pinus banskiana Lamb.); the mean pyrogenic carbon production rate for trembling aspen was 7.1%, while black spruce and jack pine had rates of 3.9% and 4.3% respectively. Smaller stick-diameters produced significantly more pyrogenic carbon than larger stick-diameters per unit mass; the mean pyrogenic carbon production rate ranged from 7.6-9.4% for 0-1cm diameter sticks, from 3.1-4.2% for 1.1-5cm diameter sticks, and was 1.3% for 5.1-7cm diameter sticks. Samples with 8% fuel moisture content produced significantly more pyrogenic carbon than those with 18% and 28% fuel moisture content; the mean pyrogenic carbon production rate was 5.8% for samples at 8% fuel moisture content, and ranged from 4.5-5.0 % for the two higher fuel moistures. The interaction between stick-diameter and fuel moisture content was also significant, with 5.1-7cm diameter sticks at 18% and 28% moisture content producing significantly less pyrogenic carbon than other samples. This research demonstrates variability in pyrogenic carbon production rates among individual forest stand components, highlighting a need to better understand the relationship between the physical characteristics of a forest and pyrogenic carbon production. With the national and global interest in the concept of carbon budgets, it becomes increasingly relevant in the field of wildland fire management to better understand the recalcitrant residues of wildland fire.