Chemical and Physical Characterization of Pre- and Post-Fire Soils for Wildfires in the Western US and Laboratory Burns

Recently, wildfire activity and intensity in the western U.S. have greatly increased, mainly due to a warming climate, population growth, land use changes, forest management, and fuel accumulation. Wildfires modify physical and chemical soil properties and can cause the formation of post-fire Soil Water Repellency (SWR), which reduces water infiltration into the soil. This may induce cascading disasters including flooding, land and debris slides, and deterioration of water quality. Despite numerous studies, chemical nature of SWR is still poorly understood, particularly at the molecular level, hindering the ability to accurately predict and mitigate post-fire hazards. Thus, this study aims to understand the effects of wildfires on soil properties through examining connections between Soil Water Repellency (SWR), reflectance spectra, and chemistry. During this study, ash and soil samples were collected after three megafires including Dixie, Beckwourth Complex, and Caldor. In addition, several field- and laboratory-based experiments were conducted on common plants in the sagebrush landscape, as well as on three standard compounds, including abietic, fulvic and hexacosanoic acids, which represent plant wax components and soil organic matter and are known to contribute to SWR. The optical, chemical, and physical properties of all the samples were studied. Optical hyperspectral reflectance spectra (350–2,500 nm) were obtained using natural solar (blue sky) illumination and a spectroradiometer (ASD FieldSpec3), operated in reflectance mode. Physical properties, including SWR were measured with Water Drop Penetration Time (WDPT) and goniometry methods. Chemical functional groups of organic compounds associated with inducing SWR of the samples were analyzed using Fourier Transform Infrared (FTIR) and Proton Nuclear Magnetic Resonance (1H-NMR) Spectroscopy. The results from temperature, reflectance, and SWR measurements were compared with data from chemical analyses of post-fire soil organic species. This work resulted in two publications, nine poster and conference presentations, and three awarded proposals.

Level thesis:degree_level

Doctorate Degree

Year dc:date.issued

2026

Author dc:creator

• Raeofy, Yasaman

Advisor dc:contributor.advisor

• Samburova, Vera

Committee members dc:contributor.committeemember

• Moosmüller, Hans
• Berli, Markus
• Furtak-Cole, Eden
• Khlystov, Andrey
• Wang, Xiaoliang
• Lutz, Alexandra

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11822

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11822