Publication Date

8-2025

Date of Final Oral Examination (Defense)

4-23-2025

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Geoscience

Department

Geosciences

Supervisory Committee Chair

Anna Bergstrom, Ph.D.

Supervisory Committee Member

Ellyn Enderlin, Ph.D.

Supervisory Committee Member

Joshua Koch, Ph.D.

Supervisory Committee Member

James McNamara, Ph.D.

Abstract

Increased temperatures over the last 40 years have globally promoted a loss of ice and increase of plant cover and density, known as greening. Greening is seen more in arctic and alpine environments than elsewhere, and current literature states that new growth consists of low-lying tundra plants, as well as encroaching shrub communities into previously uninhabited rocky slopes. However, our understanding of greening processes and extent is potentially biased by study strategies. Many vegetation studies take place at either the small plot or arctic regional scale, and do not encapsulate the intricacies of watershed scale processes on greening. This study focuses on the Nellie Juan watershed in south central Alaska, and seeks to understand the rates and mechanisms of landcover change in this coastal watershed. We analyzed Landsat data over 35 years via a random forest classification to analyze landcover change trends and relate changes to watershed topography. We observed glacier recession across the watershed, with growth of 24 km2 of new vegetation. The largest change we documented was 18 km2 of new growth of low-lying heather tundra on previously bare and ice-covered slopes between 1986 and 2021. We also noted increases in mean NDVI of 0.117 across the watershed, indicating increased productivity in all plant communities. We found that elevation and aspect are primary controls on greening, as large scale landcover changes primarily occurred on high elevation north aspects. This study confirmed greening trends are present and trackable in the subarctic via moderate scale remote sensing, and did not find shrubification as presented in arctic landcover change studies. This work presents a framework for tracking landcover changes over time at the watershed scale for the often understudied subarctic.

DOI

10.18122/td.2398.boisestate

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