Impacts of Fire-Driven Vegetation Changes on Evapotranspiration in North American Boreal Forests

Author

Tyler Glen Albrethsen, University of Montana, MissoulaFollow

Year of Award

2025

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Systems Ecology

Department or School/College

College of Forestry and Conservation

Committee Chair

Dr. John Kimball

Commitee Members

Dr. John Kimball, Dr. Arthur Endsley, Dr. Anna Klene, Dr. Kelsey Jencso

Keywords

Evapotranspiration, Land Cover, MOD16, Remote Sensing, Boreal, Model

Subject Categories

Hydrology | Other Earth Sciences

Abstract

A growing body of evidence suggests that land cover change could be impacting evapotranspiration (ET) trends more than the direct impacts of climate change (Dashti et al., 2022; Zhang et al., 2015). In boreal forests, one of the Earth’s most important carbon sinks (Kang et al., 2006), climate and disturbance-driven land cover change is progressing rapidly, threatening the resilience of conifer-dominated forests (Baltzer et al., 2021; Massey et al., 2023). The spread of deciduous trees and the changing structure of boreal forests likely have large implications for the magnitude and seasonality of ecosystem water fluxes (Young-Robertson et al., 2016). This study introduces a process-based terrestrial ET model for North American boreal forests that incorporates annual landcover (Wang et al., 2019) and estimates of vegetation characteristics derived from gap-filled optical satellite imagery (Moreno-Martinez et al., 2020) to achieve a 30-meter resolution and explicitly account for land cover change. The model was used to assess regional trends in ET and the effects of wildfire disturbance on rates of ET. Results demonstrate that ET is generally increasing across the interior boreal forests of Alaska and northwest Canada, with three quarters of the increase attributable to land cover change in recent decades. Rates of ET are also responsive to post-fire regeneration and related to corresponding trends in vegetative composition and structure. After wildfire events, ET was shown to surpass pre-fire rates after 25 years of vegetation recovery. This study provides further evidence that land cover change is driving shifts in the water cycle at higher latitudes and establishes a model for future research.

Recommended Citation

Albrethsen, Tyler G., "Impacts of Fire-Driven Vegetation Changes on Evapotranspiration in North American Boreal Forests" (2025). Graduate Student Theses, Dissertations, & Professional Papers. https://scholarworks.umt.edu