Social and Behavioral Science
127 Analysis of Charcoal Morphometrics from Known Utah Plants May Inform Fire and Vegetation History Reconstructions
Amy Harvey; Stella Mosher; and Mitchell Power (Geography)
Faculty Mentor: Stella Mosher (Geography, University of Utah)
Abstract
Fire is one of the major forces that influences vegetation type and ecosystem dynamics of an area. Reconstructing past fire regimes can help us understand not only about the type of plants that were once in an area and how they responded to fire, but also how best resource and landscape management practices can be employed to preserve present ecosystems under a changing climate. This research contributes to the reconstruction of a fire history record from Utah. A newly emerging method, the study of charcoal morphology (shape) and morphometry (particle geometries) is increasingly being used to determine the types of vegetation that have burned. Charcoal morphotypes may provide insight into the fuel type burned, and measured geometries produced by the experimental burning of plant material at a range of combustion temperatures may provide insight into fire intensity. In this research, charcoal particles collected from experimental burning of modern plant reference material were analyzed to later be compared to the morphometric analysis of macroscopic charcoal particles from local lake sediments to understand vegetation change around Utah. At each temperature (250°C, 300°C, and 350°C) there was a significant (p < 0.05) morphometric difference between each type of plant, so morphometries likely can be used to identify vegetation type of fossil charcoal. Additionally, grass-type vegetation produced charcoal that was significantly elongated compared to woody vegetation. These findings may shed light on metrics of interest to the paleofire community, such as vegetation change, wildfire temperature, and wildfire intensity.
Introduction
Past research has found that measuring aspect ratios, defined as length:width (L:W) ratios of macroscopic charcoal particles, can serve as a proxy for the fuel type burned (Feurdean, 2021; Vachula et al., 2021). Evidence suggests that some morphologies vary significantly between different plant types, specifically between grassy fuel types, signified by unitless aspect ratios greater than 3.5, and woody fuel types, signified by aspect ratios less than 2.5 (Vachula et al., 2021). Using known, modern vegetation sampled from around Utah will help to better calibrate how charcoal particles are interpreted in the deep time record by determining the shapes and aspect ratios each type of plant tends to create, then exploring whether there are significant differences between plant types or between different tissues from the same plant, such as stems and leaves, and between different combustion temperatures.
The study site chosen was the Wasatch region of Utah. Five common species were collected from Little Cottonwood Canyon: white fir (Abies concolor), big sag