Date of Award:

8-2023

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Committee Chair(s)

Andrew Kulmatiski

Committee

Andrew Kulmatiski

Committee

Jeanette Norton

Committee

Peter Adler

Abstract

Plant-soil feedback is a process through which plants modify the properties of their associated soils, affecting their growth. PSF can play a key role in regulating plant growth and communities including altering plant invasion, rarity, and abundance. However, our understanding of the soil organisms that drive these plant growth responses is limited. Most studies treat soils as a ‘black box’ and do little to reveal which specific microbes or microbial communities may be responsible. This chapter examines two recent large PSF field experiments conducted in Minnesota, USA, and Jena, Germany. These experiments revealed that plants altered their soils, changing subsequent plant growth by roughly 25%. To unravel the factors influencing soil microbial communities, we analyzed the microbial communities in these two experiments. The analysis showed that the microbial communities varied between the two study sites, among years, and between bulk and rhizosphere soils. The microbial communities differed among rhizosphere soils cultivated by different plant species, showing that plants can shape distinct microbial communities. Our analyses revealed that the differences among soils were due to the influence of the entire microbial community rather than by individual microbial species. Additionally, rather than one or two plants consistently creating soils correlated with increased or decreased plant growth, we found that several plant species from three plant functional groups created soils significantly correlated with changes in plant growth. These findings indicate that different plant growth responses are likely caused by ubiquitous, generalist microbes that differentially affect plants, rather than specific microbes that associate with only one or two plant species. These results highlight the importance of considering the entire microbial community when adopting soil management strategies, rather than focusing solely on individual soil microbes. This may lead to more effective soil and plant management practices. Additionally, we found that it may be ubiquitous, generalist microbes that differentially affect plants causing plant growth changes rather than plant-specific microbes which could explain why PSF research results are so variable and why repeat experiments often get different results. This could provide guidance to researchers investigating how to leverage soil microbes in managing plants and plant communities.

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