Date of Award

Fall 2020

Project Type

Dissertation

Program or Major

Earth and Environmental Sciences

Degree Name

Doctor of Philosophy

First Advisor

Julia G Bryce

Second Advisor

Lara Gengarelly

Third Advisor

Erik Hobbie

Abstract

Increased understanding of the impact of biology on weathering rates and its response to environmental factors will lead to more accurate global models and enhanced management practices to optimize productive, healthy forests. Although biological contributions to weathering are established in the literature, more data to translate these observations for implementation in a predictive framework should be obtained (e.g. Taylor et al., 2012). Mycorrhizal fungi have implications for global carbon cycling and increasing carbon storage in soils (Soudzilovskaia et al., 2019) but the extent of their impact is still an area of active research with more studies of local weathering sites still needed (Finlay et al., 2020; Terrer et al., 2016; Norby et al., 2017).

This dissertation examines the role that microbes can have on moderating mineral weathering and nutrient cycling in terrestrial ecosystems. My research combines geochemical data from two field studies and one controlled growth experiment with prokaryotic community composition data to determine how rock type can drive microbial weathering. Results from the two field studies, the latter including microbial community data, suggest that weathering fluxes in forest stands with different dominant mycorrhizal vegetation may be more similar than previously thought and that abiotic factors and rock composition may be responsible for weathering fluxes at the field scale. The growth chamber experiment allowed me to examine two mycorrhizal symbioses across two distinct lithologies in a controlled environment and the results suggest that mycorrhizal weathering, especially that of AM fungi, may be enhanced when nutrients aren’t readily available. Overall this work helps use to constrain the importance of biological weathering.

In the final section of my dissertation I shift my focus to look at how scientists can help engage students in authentic science practice and how this experience might build students’ self-confidence in science. I examined an established citizen science program, NASA GLOBE, and focused on how students participation in collecting data using GLOBE protocols, analyzing and reporting it, and communicating this to peers at scientists at the Student Research Symposium (SRS) helped shape students views of themselves and their confidence with science practices. Attending the SRS was seen to have a significant impact on students’ confidence in their ability to practice science (ex. “I am able to construct scientific arguments”) and their belief that they are “good at science”. I hope this work offers an example to other citizen science programs of components that can be used to engage students and improve their confidence in science.

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