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

• Main Author: Purcell, Alicia Marie
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: QH301 Biology; Antarctic; Antarctic Peninsula; Anvers; Anvers Island; Marr; Marr Ice Piedmont; Antarc*
• Online Access: https://openknowledge.nau.edu/id/eprint/5654/; https://openknowledge.nau.edu/id/eprint/5654/1/Purcell_2021_quantifying_wild_soil_microbes_warming_effects_on_taxon_g.pdf

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 ...