Biology ETDs

Publication Date

5-1-2015

Abstract

Globally, increasing human populations have either caused or accelerated several types of environmental change. Symbiotic microbes have powerful effects on plant fitness, yet little study has been done on how microbial-plant relationships are affected by environmental changes. In two different ecosystems I explore how either nitrogen (N) pollution or drought can alter root associated microbe (RAM)-plant relationships using Next Generation Sequencing. In moist-meadow alpine tundra at Niwot Ridge, CO, I examine the relative contribution of host identity, N enrichment, and plant neighborhood on RAM diversity and community composition in two co-dominant plant species; Geum rossii and Deschampsia cespitosa. In New Mexican piñon-juniper woodlands, I sampled roots from a site in which mass Pinus edulis dieback was simulated to mimic the effects of extreme drought events, which are predicted to become more frequent as climate change progresses. I examine the effect of host and neighbor identity, as well as the effect of dead P. edulis neighbors, on root associated fungi (RAF) of P. edulis and Juniperus monosperma. I also compare RAF communities between piñon-juniper woodlands and more arid juniper savanna, a good proxy for what piñon-juniper woodlands will become should these extreme drought events become more frequent. I found that biotic assembly mechanisms (plant host and neighborhood) are important to structuring RAM communities in alpine tundra but not in piñon-juniper woodlands. In the arid southwest, abiotic factors appear to be more important in structuring RAF communities, while contrary to previous research, host identity has little effect on RAF community composition. These unusual results could be a product of the more sensitive sequencing methods, or an anomaly caused by the drought experienced by these field sites at time of sampling. In both ecosystems, plant neighborhood influenced RAM (community composition in alpine tundra, diversity in piñon-juniper woodland). In alpine tundra, both host identity and plant neighborhood mediated RAM response to N. These data emphasize the complex feedback systems between environment, plant communities, and their microbes. As a plant community becomes altered in response to the environment, the response of the microbial community to the environment will shift, making plant-microbe dynamics difficult to predict.

Project Sponsors

The Biology Graduate Student Association, UNM’s Office of Graduate Studies, the Mycological Society of America, the Fungal Environmental Sampling and Informatics Network, the National Science Foundation, and the Department of Energy

Language

English

Keywords

microbiology, ecology, molecular ecology, fungi, bacteria, next generation sequencing, microbial ecology, symbiosis, root associated microbes, mycorrhizae

Document Type

Dissertation

Degree Name

Microbial Ecology

Level of Degree

Doctoral

Department Name

UNM Biology Department

First Committee Member (Chair)

Robert L. Sinsabaugh

Second Committee Member

Donald O. Natvig

Third Committee Member

Scott L. Collins

Fourth Committee Member

Andrea Porras-Alfaro

Download

Included in

Biology Commons

Share

COinS