Term of Award

Fall 2017

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

John Van Stan

Committee Member 1

Scott Harrison

Committee Member 2

Tiehang Wu


Transport pathways of microbes between ecosystem spheres (atmosphere, phyllosphere, and pedosphere) represent major fluxes in nutrient cycles and have the potential to significantly affect microbially-mediated biogeochemical processes. We quantified a previously unexamined microbial flux from the phyllosphere to the pedosphere during rainfall via throughfall (rainfall dripping from the canopy and through gaps) and stemflow (rainwater funneled down the stem). Bacterial concentrations were quantified using flow cytometry and validated with quantitative Polymerase Chain Reaction (qPCR) assays for samples from a Quercus virginiana (oak)- forest with heavy epiphyte cover (Tillandsia usneoides, Spanish moss) in coastal Georgia (Southeastern USA). Bacteria concentrations (cells mL-1) and fluxes (both cells m-2 h-1 and cells m-2 mm-1 of rainfall) were greater in stemflow relative to throughfall. However, throughfall delivers water to a larger land area (ha) resulting in throughfall producing the greatest proportion of rainfall bacteria when fluxes are modelled as cells ha-1 year-1. Annual total (throughfall plus stemflow from both species) bacterial flux was 3.4 quadrillion cells year-1 ha-1. The role of this previously unquantified bacterial flux to the forest floor may be significant by contributing functional community members (if living) or labile lysates (if dead) to soil communities. Further, bacterial community structure was characterized via Next-generation sequencing and plotted for relative abundance and diversity throughout the sampling period.

Research Data and Supplementary Material