Date of Award

2026

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Forest Science (PhD)

Administrative Home Department

College of Forest Resources and Environmental Science

Advisor 1

Steven L. Voelker

Committee Member 1

Julia I. Burton

Committee Member 2

Christopher R. Webster

Committee Member 3

Pengfei Xue

Committee Member 4

John D. Lenters

Abstract

The research presented in this dissertation focuses on developing a deeper understanding of the ecology and climate of the Lake Superior region. After an overview in Chapter 1, each of Chapters 2-4 addresses distinct research questions that are connected by the profound influence of Lake Superior on the climate, ecosystems, and people of this region. Chapter 2 uses spatial patterns in C and O tree-ring stable isotopes (δ18O and Δ13C) to investigate how the lake-effect mesoclimate influences terrestrial ecohydrology and plant physiological responses around Lake Superior. Chapter 3 describes the development of >800 years of pine establishment data, derived primarily from submerged logs preserved in lakes. These records, combined with co-located establishment data from on-land pine samples and fire history data, are used to assess how past fires influenced pine dynamics and how regional pine establishment patterns relate to fluxes of Indigenous populations into the region, first, and of Euro-American settlers, several centuries later. Chapter 4 uses various tree-ring records developed during this research, as well as others within Eastern North America, to reconstruct warm-season surface water temperature in Lake Superior back to 1500 CE. This reconstruction found that surface water temperatures over recent decades have no precedent in the past >500 years. During much of the 20th century, surface water temperatures were strongly coupled to large-scale modes of climate variability, but these connections appear to have weakened in recent decades.

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