Date of Award

2024

Degree Name

Biological Sciences

College

College of Science

Type of Degree

M.S.

Document Type

Thesis

First Advisor

Dr. Pamela Puppo, Chairperson

Second Advisor

Dr. Kyle Palmquist

Third Advisor

Dr. Todd Hutchinson

Abstract

Pollinators are declining due to climate change and habitat loss driven by agriculture and urbanization. In fire-adapted ecosystems, fire promotes the biodiversity of plants by creating space, reducing competition, and increasing light and nutrient availability. However, little is known regarding the effects of fire on floral abundance of plants used by Bombus. The overall goal of this project was to assess the long-term effects of fire on floral abundance and Bombus abundance. Our specific questions were: (1) How does fire frequency influence floral abundance?, (2) How does fire frequency influence floral abundance of species specifically utilized by bumble bees?, and (3) How does fire frequency influence bumble bee abundance? We hypothesized that plots with more frequent fire will tend to have a higher abundance of floral resources for pollinators. Vegetation surveys were conducted in 22 plots in the Wayne National Forest, Ohio. These plots are part of a fire experiment conducted from 1995 to 1999 with three treatments: frequent fire (annual), periodic fire (every 3 years), and control plots (no fire). Since the end of the experiment, periodic and frequent fire plots continued to experience burning, with sequential fires occurring in 2004, 2015, 2019. In each plot, all vascular plants species were identified, and all flowers,inflorescences, buds, and fruits were counted in 16 2 m2 quadrats (36 m2 ). Non-lethal surveys were conducted using a net to quantify Bombus abundance. Floral and Bombus surveys were conducted twice between May and September of 2022 to capture bees with different life histories. We determined which plants in our plots were considered to be focal species utilized by bumble bees and we calculated the total floral abundance of these species from our floral abundance counts. To understand what factors might be related to floral abundance, we identified predictor variables a priori (species richness, fire frequency, total cover (%), forb cover (%), woody cover (%), clay (%), sand (%), silt (%), canopy openness (%), pH, and IMI) and used model selection using corrected Akaike Information Criterion (AICc) to identify top models for total floral abundance and bumble bee host plant floral abundance. We used generalized linear models with a negative binomial distribution for each predictor variable with floral abundance separately because all predictors were significantly correlated. Model selection using AICc suggested that fire frequency and species richness, total cover (%), forb cover (%), woody cover (%), clay (%), sand (%), and silt (%) are significant predictors of total floral abundance. Total floral abundance was significantly higher in periodically and frequently burned plots relative to unburned plots. Fire enhanced the floral abundance of bumble bee host plants, especially in frequently burned plots sampled during late summer. However, total floral abundance between periodically burned and frequently burned plots did not differ and bumble bee abundance was relatively similar between no fire, periodically, and frequently burned plots. These results imply that an increase in fire frequency enhances floral abundance for bumble bees in our mixed oak forest plots.

Subject(s)

Plant ecology.

Fire management.

Pollinators.

Bees.

Wayne National Forest (Ohio).

Ohio.

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