Lakhani, Ayaan2026-01-262026-01-262026-01-262026-01-14https://hdl.handle.net/10012/22904Fire has played an integral role in the evolution, formation, and sustainability of North American forest ecosystems. Historically, Indigenous peoples have employed fire as a deliberate land management tool to maintain forest health, shape landscapes, and achieve early industrial objectives. With the landing of European settlers, and changes in governmental policy, the use of fire as a land/fuel management tool was greatly diminished. In addition to the suppression of fire as a tool, the intentional and accidental introduction of non-native plant species to Canadian forest ecosystems has dramatically altered its structure from the 17th century through to today. In addition, emissions of CO₂ and other greenhouse gases have been rapidly increasing since industrialization, which has warmed the planet, resulting in extreme weather events like droughts and storms that occur at increasing frequency and severity. This has culminated in wildfire conditions that are drastically different to those that shaped the historical evolution of Canadian forests. Key changes in forest fuels include larger spatial distributions of fuel types and moisture content, which affect fire growth and development. Over the past few decades it has become evident that understanding these factors of fuel types, moisture content, and fire growth and development are critical to improve performance of predictive models, as well as our overall understanding of how to combat and minimize the damage caused by these severe wildfire events. Assessment of wildfires has generally taken two approaches: the first being a largescale analysis of a real wildfire event, which characterizes total emissions and bulk burning behaviour, and the second being small-scale studies that often focus only on one specific fire performance metric or a limited set of emissions. While both approaches have yielded significant data in terms of bulk fire performance metrics and separate emissions data, this separation has led to a dearth of integrated, detailed, and comparative data. This comparative data is critically important because the lack of species-specific flammability metrics and associated detailed emissions data under varying conditions hinders the accurate prediction of fire behaviour and the development of effective land management strategies. Furthermore, the absence of data explicitly linking exposure conditions to trace emission profiles (the toxic fraction of smoke) leads to misestimates in both emission inventories and air quality models, potentially compromising environmental safety assessments. In this research, a pair of native species and a pair of invasive species are tested at small scale for their flammability properties, major, and trace emissions. Testing was conducted under two different levels of fuel moisture and two different radiation exposures, with twelve replicates per condition. The native species are trembling aspen and ironwood while the invasive species are buckthorn and barberry. All four species were tested under reference conditions (35 kW m⁻² incident heat flux, and naturally dry conditions), buckthorn and trembling aspen were tested under elevated heat flux (50 kW m⁻² incident heat flux, and naturally dry conditions), and barberry and ironwood were tested at elevated moisture conditions (35 kW m⁻² incident heat flux, and field-tested moisture conditions). Across the tests, flammability properties, such as ignition delay time and heat release rate, were compared as well as real-time concentrations of CO₂, CO, and VOCs. In addition to these three gases, thermal desorption tubes were employed to sample the smoke plume at three phases during a test – pyrolysis, open flaming, and smouldering – and were analyzed using GC-MS to identify and group key emissions, then develop a qualitative sensitivity of trace emissions to species and burning conditions. To properly frame the discussion surrounding the production of trace emissions, the lignocellulosic compositions (% cellulose, % hemicellulose, and % lignin) and the apparent activation energy of each of the species was determined using thermogravimetric analysis. Finally, inductively coupled plasma-optical emission spectroscopy and X-ray diffraction were employed to identify and quantify metallic emission differences in the post-burn particulate matter and the fire smoke plume. A broad summary of the results shows that species composition (lignocellulosic makeup) and intrinsic physical characteristics (sample piece sizes and packing geometry) are the dominant factors driving differences in fire performance and flammability under reference conditions. When exposed to a higher heat flux, the external energy largely overcame the impacts of geometry, allowing compositional differences to become the sole dominant factor dictating distinct species responses in peak heat release rate and emissions. The exposure to the increased heat flux also greatly reduced the ignition delay time and increased the heat release rates for both native and invasive species. Conversely, increased fuel moisture content led to a clear and consequential shift toward less efficient, incomplete combustion processes, resulting in substantial increases ignition delay time, reductions in heat release rate and increases in CO and VOC emission factors during the pyrolysis, flaming, and smouldering phases. Thermogravimetric analysis confirmed a compositional-kinetic relationship where the apparent activation energy varied by up to 24% across species. This kinetic variation, coupled with data from thermal desorption-gas chromatography–mass spectrometry, highlighted the dependent nature of trace species production on the specific species composition and apparent activation energy. Different species produced distinct groups of trace emissions and showed differing responses to both elevated heat flux (where some experienced volatile suppression and others persistent intermediates) and varying moisture conditions (where smouldering emissions were dramatically amplified or altered).enwildfiresflammability propertiesnative and invasive wildland fuelsemissionsMaster Thesis