Date of Award

Spring 1-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Katharine N. Suding

Second Advisor

Steven K. Schmidt

Third Advisor

William D. Bowman

Fourth Advisor

Noah Fierer

Fifth Advisor

Daniel F. Doak

Abstract

Over the course of Earth’s biological history, organisms have many times had to shift their geographic distributions in order to track changing abiotic conditions suitable for their growth, survival, and reproduction. Now more than ever, in the new geologic epoch of the Anthropocene, organisms will have to rapidly shift their ranges to adapt to climate change and other anthropogenic disturbances. The rearrangement of organisms can be facilitated or inhibited by biotic interactions between organisms. Here I examine plant range shifts in an alpine ecosystem in response to climate warming and earlier snowmelt, as well as the role of biotic interactions between plants and microorganisms in facilitating or limiting upwards range shifts. First, I use remote sensing to show that plants are shifting their distributions concurrently with climate warming. Then I present work from bacterial and fungal surveys to demonstrate that diverse microbial communities, including key mutualistic taxa, co-occur with some of the highest vascular plant communities in Colorado, and suggest both of these groups of microorganisms could play an important role in mediating plant range shifts. Next, I present work from a manipulative snowpack and microbial inoculation experiment that suggests plant interactions with microbes are important for plant growth and survival as they colonize previously unvegetated soils as growing seasons lengthen. Lastly, I present work on plant litter-driven plant-soil feedbacks to demonstrate how differences in litter chemistry and litter microbiomes can lead to species-specific effects on unvegetated soil microbial communities, which can then feed back and affect plant growth.

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