PhD Defense by Xian Yang

Event Details
  • Date/Time:
    • Thursday October 31, 2019
      9:30 am - 11:30 am
  • Location: Marcus Nanotechnology Building Conference Room 1116
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Summaries

Summary Sentence: Ecological Community Assembly in the Face of Anthropogenic Environmental Changes

Full Summary: No summary paragraph submitted.

 

In partial fulfillment of the requirements for the degree of 

 

Doctor of Philosophy in Biology

in the 

School of Biological Sciences

 

Xian Yang

 

will defend her dissertation

 

Ecological Community Assembly in the Face of Anthropogenic Environmental Changes

 

Thursday, October 31, 2019

9:30 AM

            Marcus Nanotechnology Building

Conference Room 1116

 

Thesis Advisor:

Dr. Lin Jiang

School of Biological Sciences

Georgia Institute of Technology

 

Committee Members:

Dr. Mark E. Hay

School of Biological Sciences

Georgia Institute of Technology

 

Dr. Marc J. Weissburg

School of Biological Sciences

Georgia Institute of Technology

 

Dr. Linda E. Green

Department of Biology

Georgetown University

 

Dr. Nathan J. Sanders

Rubenstein School of Environment and Natural Resources

University of Vermont

 

Abstract

Anthropogenic environmental changes, such as increased nitrogen (N) deposition, changes in precipitation regimes, and habitat loss and fragmentation, are known to affect Earth’s ecosystems. Understanding mechanisms regulating the assembly of ecological communities in the face of anthropogenic environmental changes is one of the primary goals of contemporary ecology. In this dissertation, I present four studies addressing questions on community assembly under anthropogenic environmental changes. First, I conducted an experiment in a semi-arid grassland to examine how anthropogenic environmental changes, in the form of resource addition, influence phylogenetic alpha- and beta-diversity of the communities. I found N and water addition influenced different aspects of the grassland community structure. N addition altered plant community phylogenetic structure, driving communities towards phylogenetic overdispersion; water addition promoted phylogenetic convergence, driving communities to converge towards a more similar phylogenetic structure over time. Next, I used bacterivorous ciliated protists as model organisms to explore how the loss of a keystone local community affects metacommunity biodiversity and ecosystem functions. I found that local communities with distinct environmental conditions supported endemic species, and had greater impact on regional-scale diversity than other local communities, therefore qualifying them as keystone communities. These keystone communities also had significant impacts on ecosystem functions, including biomass production and particulate organic matter decomposition. Finally, I investigated the drivers of variation in the phyllosphere microbial community composition in a fragmented subtropical forest on the islands of the Thousand-Island Lake, China. I found that stochastic processes, rather than deterministic processes, played a prominent role in shaping phyllosphere bacterial and fungal communities in the context of habitat fragmentation. Taken together, these findings further our understanding of community assembly processes in the face of anthropogenic environmental changes.

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Phd Defense
Status
  • Created By: Tatianna Richardson
  • Workflow Status: Published
  • Created On: Oct 17, 2019 - 11:24am
  • Last Updated: Oct 17, 2019 - 11:24am