Project Title: Investigating the effect of competition on the growth and survival of the coastal sand
dune shrub Sea Elder
Principal Investigator: Dr. Heather Joesting (Assistant Professor of Biology)
The original aim of the Summer 2015 research in the Joesting lab was to investigate the effect of
competition on the growth and biomass of the sea elder (Iva imbricata), a perennial coastal sand
dune shrub (as was proposed for the Research and Scholarship Internal Grant). The project was
proposed to and approved by the Sapelo Island National Estuarine Research Reserve (NERR)
during the Spring 2015 semester after an initial site visit to Sapelo Island, GA. On this initial visit
in late April (at the beginning of the growing season for this plant species), very few individuals of
sea elder were located within the sand dune habitat on Sapelo Island. Since it was difficult to
estimate if there would be an adequate number of individuals within the sand dune system by the
beginning of the research (late May to June 2015), an alternative project was proposed to Sapelo
Island NERR to monitor seasonal and diurnal leaf morphology and physiology for the beach croton
(Croton punctatus), a perennial shrub common to the sand dunes of Georgia barrier islands. At the
onset of the summer research season, only one sea elder individual was located at the study site on
Sapelo Island, and thus, the alternative project was conducted in Summer 2015.
The goal of the alternative project was to examine the seasonal and diurnal leaf morphology
and physiology of beach croton within the sand dune environment on Sapelo Island, GA, to better
understand how this species has adapted to the abiotic factors of the habitat. Four undergraduate
students were actively involved in all aspects of this research, including experimental design, field
and laboratory data collection, and data analysis. Two trips to the study site on Sapelo Island were
completed June 1 – 2 and July 6 – 7, 2015. These trips involved a round-trip ferry ride to Sapelo
Island, field sampling from late morning to early evening on Day 1, an overnight stay at the
University of Georgia Marine Institute dormitory, and field sampling the following day (Day 2)
from early morning to midday. Two 20-m transects were established in the field and beach croton
individuals were identified along each transect. Weather stations equipped with sensors to measure
incident sunlight, air temperature, and sand temperature were erected at the beginning and end of
each transect. Diurnal measurements of leaf temperature, incident sunlight on the top and bottom
leaf surfaces, and photosynthetic activity, in addition to measurements of plant height, plant
diameter, and leaf salt deposition, were made in the field for each individual per transect. Leaves
were collected from the field and analyzed in the lab for leaf area, leaf width, leaf fresh and dry
weight, leaf chlorophyll content, and leaf trichome density on both the top and bottom of leaf
surfaces.
By the end of the Summer 2015, all field data was collected and most lab analyses were
completed. Two of the undergraduate research students will continue the remaining lab analyses,
in addition to data entry and data analysis for all collected data, in the Fall 2015 semester. One of
the undergraduate students involved has been named a 2015-16 Georgia Power Scholar and will
give an oral presentation on this research at the 2016 Armstrong Student Scholar Symposium. A
second undergraduate student will also present a portion of this research during the poster session
of the Student Scholar Symposium.
Additionally, this research will be presented by the
undergraduate students and myself at a major scientific meeting, Botany 2016, to be held in
Savannah, GA, July 30 – August 3 2016. Finally, a manuscript will be prepared for submission to
a peer-reviewed journal with both undergraduate students as co-authors.