Year of Award


Document Type


Degree Type

Doctor of Philosophy (PhD)

Other Degree Name/Area of Focus

Integrative Microbiology and Biochemistry, Microbial Ecology

Department or School/College

Department of Chemistry and Biochemistry

Committee Chair

Matthias C. Rillig

Commitee Members

James Gannon, William Holben, Scott Miller, Tom Deluca, Paul Alaback


Micorbial Ecology, Mycorrhial Succession, Mycorrhizae


University of Montana


Arbuscular mycorrhizal fungi (AMF) are soil fungi associations with the majority of terrestrial plants. These fungi may affect a wide range of ecosystem processes from primary productivity to soil stabilization. Understanding the patterns and controls of AMF abundance during succession soil will be critical to predicting and managing ecosystem development. The work presented in chapter 2 is the first to describe changes in the abundance of mycorrhizal types during development of an unregulated floodplain. These findings are important to floodplain regulation and management strategies as they suggest that flow regulation that limits early site formation will limit the ecosystem contributions of AMF on dammed rivers. Chapter 3 builds on the findings from chapter 2 to determine the mechanisms of how litter may affect the abundance of a native AMF community. We test the hypothesis that litter from cottonwoods (Populus sp.) is inhibitory to AMF colonization. Our works shows that even small amounts of litter and realistic concentrations of litter leachates can strongly inhibit AMF colonization of two plant species, and that this inhibition is not solely a result of changes in the soil nutrient status. Chapter 3 also demonstrates that common soluble phenolics found in cottonwood litter are inhibitory to AMF at ecologically realistic concentrations, whereas other root colonizing fungi are unaffected. These findings offer another explanatory mechanism for the shift we and others have observed between AMF and ECMF during succession. Chapter 4 addresses the potential consequences of a changing AMF community with respect to the key AMF mediated process of soil stabilization. This work is the first to document a significant interaction between co-occurring species of plants and AMF in soil aggregate formation. Chapter 5 synthesizes our findings with others to understand the potential consequences and management options to control AMF succession and species composition in agroecosystems. Chapter 6 is a product of my work with the ECOS program, and is a lesson on the importance of soil organic matter that is designed for the youngest of students. The significance of this body of work is discussed in chapter 7.



© Copyright 2007 Jeffrey Scott Piotrowski