Date of Award

2021

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

Evan Kane

Advisor 2

Rodney Chimner

Committee Member 1

Katherine Heckman

Committee Member 2

Noel Urban

Committee Member 3

Andrew Burton

Abstract

We sought to quantify the fire regimes of peatlands in the hemi-boreal zone of North America, and to understand the qualities of their peat. We used infrared spectrometry to accomplish both goals by gathering spectral information about the organic matter in each sample. We used a series of mixtures of natural peat and natural peat charcoal to isolate the spectral components associated with charcoal concentration. We built a multiple linear regression model which predicts the charcoal concentration in peat samples. We validated our data using nuclear magnetic resonance spectrometry. As a result, we can accurately predict the charcoal concentration of peat samples using only their infrared spectra. Applying this method, we analyzed the charcoal concentration throughout the peat profile in 29 sites in the hemi-boreal region of North America. These sites fell into four peatland ecotypes common in the hemi-boreal region, three types of poor fens, differing by tree cover, and forested rich fens. We found that the poor fen ecotypes had a mean fire return interval of 480 years, while the forested rich fens usually had no evidence of fire. We also found that fire frequency was negatively correlated with carbon accumulation in the poor fen ecotypes. These findings indicate that fire is a normal part of poor fen ecosystems but is rare in forested rich fens. Significant changes to these norms could have deleterious consequences for these ecosystems. We also performed analyses to compare the peat quality of these same ecotypes to one another. Peat quality refers to molecular lability. We were able to consider peat quality throughout each core. We identified that forested peatlands had more consistent, lower peat quality than open fens, which had high quality surface peat that declined in quality rapidly. Overall open poor fens had the highest peat quality, followed by forested poor fens, and finally forested rich fens. This implies that open poor fens are more vulnerable to both short- and long-term disturbances to temperature or water levels. Our research contributes knowledge that equips ecologists, managers, and policy makers to better understand, plan for, and conserve peatlands in our changing world.

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