Date of Award

2021

Degree Name

Biology

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Kyle Palmquist, Committee Chairperson

Second Advisor

Dr. Todd Hutchinson

Third Advisor

Dr. Anne Axel

Fourth Advisor

Dr. Shane Welch

Abstract

In the eastern U.S., fire is a natural disturbance process in Quercus (oak) forests. Fire is thought to promote oak regeneration and plant diversity by reducing competition, preparing a suitable seedbed, and increasing light availability. However, the era of fire suppression that began in the early 20th century is thought to have negatively impacted oak regeneration and the biodiversity of the understory layer. In this study, we examined the effects of prescribed fire on tree regeneration and the understory layer over 25 years. From a study initiated in 1994, we resampled 45 permanent vegetation plots measuring 1250 m2 across three fire treatments (unburned, burned every three years, annually burned) in the Wayne National Forest, Ohio. Pretreatment data was collected in 1995, low-intensity prescribed burns were conducted during 1996-1999, and that was followed by a somewhat fire-free period. Herbaceous plants, woody plants, and tree seedlings were tallied and identified in 16 quadrats measuring 2 m2 , and saplings were tallied and identified in 312.5 m2 . Using linear models and model selection using Akaike information criterion (AIC), we examined if seedling and sapling density changed from 1995 to 2019 and 2002 to 2019 in relation to fire, light availability, soil nutrients, and soil moisture. Changes in species richness for the understory layer was examined using linear mixed effects models. Differences in species composition were examined using Bray-Curtis dissimilarity, nonmetric multidimensional scaling, and permutational analysis of variance (PERMANOVA). Through time, Quercus saplings increased on some burned xeric areas (p < 0.01), while Acer seedlings and saplings decreased regardless of fire treatment and soil moisture (p < 0.01). Soil texture, forest structure, Integrated Moisture Index, and soil macronutrients were most related to changes in Quercus sapling density from 1995 to 2019. For the understory layer, species richness increased on burned areas through time (p < 0.01) and differences in species composition between fire treatments were significant (p = 0.05), with no significant effect of soil moisture for either changes in species richness or composition. Our results indicate that prescribed fire positively influenced Quercus regeneration on xeric sites and understory species richness across the moisture gradient over 25 years.

Subject(s)

Forest landscape management.

Prescribed burning.

Fire ecology.

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