Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Biology

Program Name/Specialization

Integrative Biology

Faculty/School

Faculty of Science

First Advisor

Jennifer Baltzer

Advisor Role

Supervisor

Abstract

Up to 80% of the boreal biome is found within permafrost regions, and with rapid high latitude warming, widespread thaw is occurring. As permafrost thaws, the seasonally-thawed active layer thickens, increasing resource availability and plant productivity. Caribou lichen (predominantly Cladonia spp.) forms a critical winter food resource for caribou, a threatened species identified as a conservation priority by Federal, Territorial, and Indigenous governments. Caribou lichen proliferates in regions of low productivity, such as soils underlain by permafrost. Permafrost thaw may directly affect lichen through ground surface deformation and/or ponding, or indirectly via increases in aboveground biomass and associated reductions in light availability. To assess these relationships, we used long-term permafrost monitoring paired with vegetation surveys at sites across a latitudinal gradient from 61°N-69°N in the Northwest Territories, Canada. We used Generalized Linear Mixed Models to assess caribou lichen biomass as a function of permafrost conditions and environmental variables. We evaluated 1) how permafrost conditions affect caribou lichen biomass using permafrost extent (continuous, discontinuous, and sporadic), depth (shallow and deep/absent), and stability (aggrading, stable, and degrading) metrics; 2) the effect of key biotic (plant community) and abiotic (site drainage and fire history) drivers of caribou lichen biomass in permafrost landscapes; and 3) the relative importance of permafrost conditions compared to these biotic and abiotic variables. Continuous, shallow, and aggrading permafrost were all associated with greater caribou lichen biomass. These permafrost conditions limit plant growth, allowing caribou lichen to proliferate with reduced competition. Plant community composition was the most important biotic variable, with greater lichen biomass associated with open canopy plant communities. Site drainage was the most influential abiotic variable, where wet sites had greater lichen biomass compared to mesic or dry sites. Both biotic and abiotic variables were more important predictors than permafrost conditions. However, permafrost may indirectly impact lichen through its impacts on plant community composition and site moisture. More intact permafrost supported greater caribou lichen biomass, meaning that as climate warming drives continued permafrost thaw, caribou lichen habitat quality will likely be reduced in some regions. This study advances our knowledge of climate warming-induced disturbances on caribou forage.

Convocation Year

2026

Convocation Season

Fall

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Available for download on Thursday, May 27, 2027

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