Portland State University. Department of Environmental Science and Management
Term of Graduation
Date of Publication
Master of Science (M.S.) in Environmental Science and Management
Environmental Science and Management
1 online resource (x, 76 pages)
Snow-water storage is decreasing, while forest fires are increasing in duration, size, frequency, and intensity, due to climate change. Most forest fires occur in the seasonal snow zone, altering snow mass and energy balance for many years following fire. Following forest fires, Surface snow albedo (SSA) decreases, as light absorbing particles (LAP), particularly black carbon (BC) produced in forest fires get deposited throughout the snowpack, altering snowpack energy balance driving earlier snowmelt in burned forests. While SSA decreases, landscape snow albedo (LSA) increases following fire, as more of the snow-covered surface becomes visible beneath the burned forest canopy, brightening the snow albedo of the broad-scale landscape surface. Altered snow albedo has major hydrologic and climatic implications, impacting the environment and human life. We used MOD10A1 from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument to acquire daily snow albedo data from January 1st - April 30th, 2000 - 2019. The daily snow albedo was evaluated before and after fire occurrences, across a chrono-sequence of eight burned forests, relative to burn severity, years since fire occurrence, and forest density. LSA displayed a persistent increase for at least ten years following a fire, with a total increase of 33% across all eight forest fires and burn severity classifications over the entire temporal analysis. Two-thirds of that increase came the year immediately following the fire. High burn severity LSA observed a total increase of 63%, the highest difference for all burn severity classifications for the study. Moderate burn severity and unburned forest LSA saw an increase of 53% and 51%, respectively. When we examined seasonal LSA following a fire, winter experienced higher-than-average values whereas spring experienced lower-than-average values. For the post-fire analysis, a generalized additive model (GAM), multivariate linear regression models, and linear spline regression models of normalized LSA indicated that following the initial increase in LSA due to a forest fire disturbance, LSA remains relatively constant, increasing only slightly each year, until approximately six years post-fire, where a change in the rate of increase becomes greater, resulting in a delayed brightening effect in LSA. Therefore, resulting in a large portion of post-fire snow albedo change (PFSAC) to occur between the period of six to ten years post fire. The results indicated that the rate of increase in LSA slowed after approximately ten years following a fire, suggesting LSA in previously burned forests progress to become like that of an unburned, open meadow.
© 2021 Max Gersh
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Gersh, Max, "Forest Fire Effects on the Temporal Variability of Landscape Snow Albedo Relative to Burn Severity" (2021). Dissertations and Theses. Paper 5800.