Date of Award

8-2020

Degree Type

Thesis

Degree Name

Master of Science

Department

Biology

Program

Biology

First Advisor/Chairperson

Alan Rebertus

Abstract

Inonotus obliquus, a conk forming polypore parasitic to birch (Betula spp.) trees in northern hardwood forests around the world, has been harvested intensively in recent years for its potentially medicinal properties. However, there is a dearth of ecological understanding of this fungus; even basic infection rates tend to be anecdotal or lack statistical rigor to guide new research and provide management guidelines ensuring sustainable harvest. Here I determine factors influencing conk formation at tree level by constructing a generalized linear mixed-effects model to predict host infection status, estimate infection rates in a variety of forest types and compare statistical methods for doing so, and examine basic morphological characteristics of conks. The study area included forest stands of diverse age and species compositions with different densities of birch at 11 sites throughout the Laurentian Mixed Forest Province. My surveys suggest I. obliquus infection rates are not dependent on host density but rather forest type, with the highest rates observed in mature forests of mixed species. Infection rates ranged from 1.36 to 5.9% ± 2.28 (95% CI). Belt transects are an efficient method to quickly estimate infection rates in stands, but I provide guidelines for sample sizes required to achieve desired levels of precision. At tree level, my model indicates infection status is predicted by DBH, tree species, and crown condition, with larger, older yellow birch in poorer condition more likely to bear conks.

Access Type

Open Access

Justification for Restricting Access

Manuscript is to be published in a journal.

Available for download on Monday, August 04, 2025

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