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Quantifying wild soil microbes: warming effects on taxon growth in the field

Purcell, Alicia Marie (2021) Quantifying wild soil microbes: warming effects on taxon growth in the field. Doctoral thesis, Northern Arizona University.

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Abstract

Microbes are dominant biota in soil where they interact with each other and plants, control nutrient cycling and greenhouse gas emissions, and determine carbon storage and release. Microbial communities and their activities are sensitive to temperature. The main goals of this dissertation are to obtain environmentally relevant measures of soil microbial growth in the field, quantify differences of the growing microbial communities in response to warming, and understand what drives this warming response. In Chapter 1, I introduce the theme of my dissertation which is that individual microbes are diverse in identity, function, and in their response to climate warming. I highlight the knowledge gaps in soil microbial ecology and why we must study individual microbes in a quantitative way. In Chapter 2, I introduce the main method used in this dissertation to quantify microbial growth, quantitative stable isotope probing (qSIP) with 18O-H2O. In Chapter 3, I determine if laboratory-based measurements of microbial growth inform field-based measurements of microbial growth and show that they do not. The remaining chapters utilize this field qSIP technique to quantify taxon-specific growth rate responses to warming in two ecosystems. Chapter 4 includes results from an elevation gradient transplant soil warming experiment from a mixed conifer forest, where plant-soil mesocosms were transplanted 15 years prior to a lower elevation site, the ponderosa pine forest. This experiment found that microbes decreased their growth rate with warming, likely due to a depletion in available carbon. The last two dissertation chapters focus on a short-term warming experiment to measure field growth rates of taxa in two sites along the Marr Ice Piedmont glacier chronosequence on Anvers Island, Antarctic Peninsula. In Chapter 5, I show that most microbial taxa increased their growth rate with warming. In Chapter 6, I show that phylogenetically related microbes did not grow or respond to warming at a similar rate, except for the early succession, bare fell-field soil that likely received an increase in available substrate from autotrophs responding to warming. I also determined that some functional groups including taxa involved in carbon and nitrogen cycling increased their growth rates significantly with warming. These studies provide valuable information for understanding microbial taxa activity, carbon and nutrient dynamics, and responses to environmental change, summarized in Chapter 7.

Item Type: Thesis (Doctoral)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: climate warming; field microbial taxon-specific growth rates; long-term warming elevation gradient transplant; quantitative stable isotope probing; short-term warming Antarctica; wild microbial ecology
Subjects: Q Science > QH Natural history > QH301 Biology
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited: 04 Feb 2022 21:04
Last Modified: 04 Feb 2022 21:04
URI: https://openknowledge.nau.edu/id/eprint/5654

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