Term of Award

Spring 2014

Degree Name

Master of Science in Biology (M.S.)

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.


Department of Biology

Committee Chair

Checo Colon-Gaud

Committee Member 1

Scott Harrison

Committee Member 2

Tiehand Wu


Microbial communities associated with decaying leaves play an important role in the cycling of nutrients in stream ecosystems. In headwater streams that are deemed as heterotrophic, bacteria and fungi are main drivers of organic matter decomposition and thus partly responsible for facilitating the cycling of nutrients from leaves that fall into the stream. The main objective of this study was to compare microbial community composition between different leaf types during breakdown in stream ecosystems. To achieve this objective, I used a combination of field and laboratory trials. Field experiments were performed at the Luquillo Experimental Forest using Dacryodes excelsa and Cecropia schreberiana leaves in June 2012 and at the Coweeta Long Term Ecological Research site using Acer rubrum and Quercus prinus leaves in June 2013. Laboratory trials using the same leaf types were set up in experimental chambers to model the systems found in these two regions. Decay rates and microbial communities were analyzed for individual leaf types during field and laboratory experiments. Although decay rates between leaf types in the field experiment did not differ, results from the laboratory trials suggest that A. rubrum has higher decay rates and thus decomposes faster than the other leaf types examined. Results also suggest that individual taxa colonizing leaves differed between leaf types but microbial community richness and Shannon’s diversity did not differ. These results suggest that different leaf types may harvest unique microbial communities responsible for facilitating the decay process even if these leaves are exposed to similar environmental conditions (i.e., decaying in the same stream or region).

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