School of Civil and Environmental Engineering

Ph.D. Thesis Defense Announcement

Elucidating How Global Climate Change Factors Affect Soil Microbial Carbon Cycling Processes:  From Tropical Forests to the Alaskan Tundra

By

Eric Robert Johnston

Advisor:

Dr. Konstantinos T. Konstantinidis (CEE)

Committee Members:

Dr. Spyros Pavlostathis (CEE), Dr. Joe Brown (CEE),
Dr. Joel Kostka (BIOL), & Dr. James Tiedje (CME, MSU)

Date & Time: Thursday, August 9th, 2018, 10:00 AM

Location: Ford ES&T L1125

Soils harbor a large reservoir of carbon (C) that is several times greater than the amount present in the atmosphere. How climate change factors will affect microbial turnover of organic C (OC), resulting in release of C to the atmosphere, remains uncertain. Closing these knowledge gaps is necessary for improving predictions of future climate change and managing natural as well as agricultural ecosystems. To advance these topics, we have studied the responses of soil microbial communities to key climate change factors in tundra, temperate, and tropical ecosystems. Moderate warming of tundra soils (1-2°C above ambient) increased microbial potential for CO2 and methane production after just five years. Several of the most dominant and responsive taxa were also found to be widespread throughout the surrounding ecosystem. A similar study of Eurasian steppe soils revealed how warming stimulates microbial mechanisms involved in C release, but how the combination of increased temperatures and precipitation counteracts C loss through increased plant productivity. A study of phosphorus (P)-limited tropical soils revealed how P availability regulates microbial OC turnover, which has implications for the management of tropical ecosystems because enhanced plant growth is expected to increase OC and decrease P bioavailability. Collectively, these studies contribute to an improved understanding of the diversity and functionality of terrestrial soil microbiota and how future climate change might affect soil C release.