Leveraging Fourier Transform Infrared Spectroscopy to Elucidate Post-Fire Chemical Changes
Loading...
Authors
Minatre, Kerri Lynn
Issue Date
2024
Type
Dissertation
Language
en_US
Keywords
Alternative Title
Abstract
Vegetation fires are a natural and common occurrence in forest ecosystems of the Sierra Nevada, resulting in changes to soils, vegetation, and hydrology. To successfully manage challenges of increased severity and frequency of fire and ensure the long-term health and sustainability of Sierra Nevada landscapes, continuous monitoring, and adaptive management efforts are needed. Land management strategies in fire-affected ecosystems require novel approaches that address soil water repellency (SWR), enhance water retention, and support vegetation recovery while acknowledging impacts on ecosystem resilience. This dissertation examined the relationships among temperature, charcoal, and SWR. First, laboratory methods of charcoal production in a controlled muffle furnace were compared with replicated fire conditions in a combustion facility. The heat-related chemical transformations of the produced charcoal were also compared using Fourier Transform Infrared (FTIR) spectroscopy and statistical analysis using Modern Analogue Technique (MAT). Mixed responses were observed when using FTIR spectra to infer fire temperature and vegetation species by measuring temperature changes in charcoal chemistry. Then, field-based data were collected to examine the relationships between burn severity, hydrophobic compound ratios, and infiltration rates for historic vegetation fire sites in the Sierra Nevada. An inverse relationship was found between hydrophobiccompound ratios, measured using FTIR, and soil water infiltration, emphasizing SWR in influencing post-fire soil hydrology. Finally, changes in the chemistry of vegetation fire collected charcoal to infer fire temperature using FTIR spectra were combined with infiltration measurements to examine temperature thresholds of SWR. Results showed that the relationship between charcoal temperatures collected from SWR soils needed to be clarified. Most charcoals had inferred temperatures above the threshold shown for SWR soils to occur, suggesting that charcoals could have been deposited from tree crowns and do not necessarily represent temperatures reached during fire for local soil microsite conditions. This study enhances our understanding of charcoal pyrolysis temperatures through FTIR analysis from a chemical standpoint. These findings have important implications for land management in fire-impacted ecosystems, highlighting the need forstrategies that mitigate soil erosion, improve water retention, and promote vegetation recovery, all while considering the role of SWR in ecosystem resilience.