Tindall defended her master’s thesis!

Photo of woman in front of mountains

Excitingly, master’s of science graduate student Tindall Ouverson successfully defended her thesis! Tindall is a student at Montana State University, and took over a collaborative project that stretches back when I left my postdoc position (to head to another job) in the Menalled Lab in 2017. Earlier this year, her first scientific paper was published, Temporal soil bacterial community responses to cropping systems and crop identity in dryland agroecosystems of the Northern Great Plains. More recently, she won first prize in the graduate students poster competition at the 2021 Montana State University LRES research colloquium.

Now that she has defended, Tindall will focus on revising the research thesis chapter which was not already published into a manuscript to submit for review at a scientific journal. After that, she is planning on pursuing her career in agricultural sustainability research and outreach.

RESPONSE OF SOIL BACTERIAL COMMUNITIES TO CROPPING SYSTEMS, TEMPORAL CHANGES, AND ENVIRONMENTAL CONDITIONS IN THE NORTHERN GREAT PLAINS

by

Laura Tindall Ouverson

Master of Science

Land Resources and Environmental Sciences

MONTANA STATE UNIVERSITY

Bozeman, Montana

July 12 2021

ABSTRACT

Soil bacterial communities are essential components of the soil ecosystem that support crop production and indicate a soil’s health. However, agriculture in semiarid drylands and their associated soil bacterial communities face increasingly warmer and drier conditions due to climate change. Two complementary studies were conducted to assess the response of soil bacterial communities to cropping systems, temporal changes, and soil temperature and moisture conditions in semiarid, dryland agricultural systems of the Northern Great Plains. 

The first study focused on soil bacterial community response to crop phase (i.e., crop species) of a rotation in contrasting cropping systems (chemical inputs and no-till, USDA-certified organic tilled, and USDA-certified organic sheep grazed) over a growing season. Organic grazed management supported more diverse bacterial communities than chemical no-till, though diversity in all systems decreased over the growing season. Organic grazed bacterial communities were distinct from those in the organic tilled and chemical no-till systems. An interaction between cropping system and crop phase affected community dissimilarity, indicating that overarching management systems and environmental conditions are influential on soil bacterial communities.

The second study evaluated soil bacterial communities in a winter wheat-cover crop or fallow rotation. Observations were conducted in the summer fallow and two cover crop mixtures differing by species composition and phenologies, terminated by three different methods (chemical, grazing, or haying), and subjected to either induced warmer/drier or ambient soil conditions. Only the presence and composition of cover crops affected bacterial community dissimilarity. Bacterial communities responded to an interaction between the presence and composition of cover crops and environmental conditions, but not termination. Additionally, soil bacterial communities from mid-season cover crops were distinct from early season and fallow. No treatments affected bacterial communities in 2019, which could be attributed to historic rainfall. Cover crop mixtures including species tolerant to warmer and drier conditions can foster diverse soil bacterial communities compared to fallow soils.

Overall, these studies increased our understanding of how soil bacterial communities respond to soil health building practices in the Northern Great Plains. Cropping systems can foster unique soil bacterial communities, but these effects may be moderated by environmental and temporal conditions.

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